Definition

ABCA1 is a protein that pumps cholesterol out of cells and hands it to HDL particles for the trip back to the liver.

Why it matters

It is the first step of reverse cholesterol transport. People with two broken copies develop Tangier disease, with almost no HDL at all — a natural experiment in what HDL actually does.

Definition

Absolute risk is the real chance that something will happen to you, written as a percentage. If your absolute risk of a heart attack in the next ten years is 12 percent, that means about 12 out of every 100 people like you would have one.

Why it matters

This is different from relative risk, which only compares two groups. A drug that cuts risk by 25 percent sounds huge, but if your starting risk was tiny, the real-world benefit is tiny too. Always ask about the absolute number.

Definition

ACCORD was a large trial testing whether driving blood sugar down very aggressively in people with type 2 diabetes would prevent heart attacks.

Why it matters

It did not, and the intensive arm had more deaths. The lesson was that lowering a number is not automatically the same as helping the patient — a theme that recurs throughout cardiology.

Definition

Added sugar is sugar that gets put into food during processing or cooking, rather than sugar that occurs naturally in fruit or milk.

Why it matters

Too much added sugar can raise triglycerides, add body fat around the middle, and push the body toward insulin resistance. All three of these make heart disease more likely.

Definition

Adherence means actually taking your medicine the way it was prescribed, day after day.

Why it matters

This matters more than most people realize. Cholesterol medicines work by lowering your particle count over many years. Skipping doses doesn't just reduce the benefit a little — it can erase most of it, because the protection comes from the total exposure over time.

Definition

Adjudication is the process in which an independent committee reviews each reported event in a trial and decides what actually happened, without knowing which treatment the patient received.

Why it matters

It stops enthusiasm from shaping the results. Whether a hospital visit counted as a heart attack should not depend on which arm of the trial the patient was in.

Definition

The adventitia is the tough outermost layer of an artery, made largely of connective tissue, nerves, and the small vessels that feed the wall.

Why it matters

It was long treated as packaging. It is now understood to take an active part in inflammation and in how an artery reshapes itself as plaque grows.

Definition

Aerobic exercise is steady activity that gets you breathing harder for a while, like walking fast, cycling, swimming, or jogging.

Why it matters

It improves fitness, blood pressure, blood sugar, and how well your blood vessels work. It is one of the best things you can do for your health. But it does not lower your ApoB particle count very much, which is why very fit people can still have plaque.

Definition

The Agatston score is the specific formula used to turn a calcium CT scan into a single number, weighting each calcium deposit by how dense and how large it is.

Why it matters

When someone says "my calcium score is 150," this is the scale they mean. Because it weights density, two people with similar amounts of calcium can score differently.

Definition

Alcohol is the ingredient in beer, wine, and spirits that makes them intoxicating.

Why it matters

For years people were told a daily glass of wine was good for the heart. Newer and better studies have taken that idea apart. The people who drank lightly were healthier for other reasons. Alcohol raises blood pressure and triglycerides, and there is no amount that doctors recommend for heart protection.

Definition

Alirocumab, sold as Praluent, is an injectable antibody that blocks PCSK9, given every two to four weeks.

Why it matters

It lowers LDL and ApoB by roughly half on top of a statin, and reduced repeat events in patients recovering from a heart attack.

Definition

Alzheimer's disease is a brain illness that slowly destroys memory and thinking.

Why it matters

It used to be treated as completely separate from heart disease. Newer research suggests the two share more than we thought, including the same cholesterol-carrying particles and damage to the tiny blood vessels that feed the brain.

Definition

Anabolic resistance is when older muscles stop responding well to protein. A younger person can eat a modest amount of protein and build muscle. An older person eating the same amount may build almost none.

Why it matters

This is why protein needs go up with age rather than down, especially for older athletes trying to hold onto muscle.

Definition

Angina is chest discomfort that happens when the heart muscle isn't getting enough oxygen. People describe it as pressure, tightness, squeezing, or burning, and it can spread to the arm, neck, or jaw.

Why it matters

Not everyone gets classic chest pain. Some people just feel short of breath, unusually tired, or sick to their stomach. Very fit people sometimes feel almost nothing at all, which is exactly what makes their disease dangerous.

Definition

An angiogram is a test where doctors thread a thin tube into your arteries and inject dye, so the inside of the arteries shows up on an X-ray.

Why it matters

It shows the open channel that blood flows through. Its big weakness is that it does not show the artery wall — and plaque grows in the wall. An artery can look almost normal on an angiogram while carrying a lot of disease.

Definition

Angioplasty is a procedure where a small balloon is inflated inside a narrowed artery to push the blockage open. A stent is usually left behind to hold it open.

Why it matters

It is very good at relieving symptoms and saving lives during a heart attack. What it does not do is fix the disease itself, which is spread throughout all your arteries, not just the one spot that got fixed.

Definition

ANGPTL3 is a protein that slows the breakdown of triglyceride-rich particles in the blood.

Why it matters

People born with a broken copy have low triglycerides, low LDL, and less heart disease — which made it an obvious drug target. Evinacumab blocks it and is used in the most severe inherited cholesterol disorders.

Definition

An anticoagulant reduces the blood's ability to clot by interfering with clotting proteins. Warfarin and apixaban are examples.

Why it matters

It is a different tool from aspirin, which acts on platelets instead. Anticoagulants are used for atrial fibrillation and clots in veins; using one where the other is needed leaves a person poorly protected.

Definition

An antioxidant is a substance that mops up damaging molecules in the body. Vitamin E and beta-carotene are examples.

Why it matters

The theory sounded great, and antioxidant pills were popular for years. But when researchers actually tested them in large trials, they did not prevent heart attacks, and a few appeared to cause harm. It is a good reminder that a sensible-sounding idea still has to be tested.

Definition

Antiplatelet therapy uses drugs that make platelets less likely to clump — aspirin, clopidogrel, ticagrelor.

Why it matters

It is the mainstay after a stent or a heart attack, where a clot forming on a damaged or instrumented surface is the immediate danger. The benefit is always weighed against bleeding.

Definition

The aorta is the biggest artery in your body. It carries blood out of the heart and down through the chest and belly, sending branches everywhere.

Why it matters

Because it handles so much pressure, it can stretch, stiffen with age, or develop a bulge. In athletes, the aorta is often slightly larger than average, which raises questions about what counts as normal.

Definition

An aortic aneurysm is a bulge in the wall of the aorta, like a weak spot on a garden hose.

Why it matters

Small ones often cause no trouble and are simply watched over time. Larger ones can tear or burst, which is a life-threatening emergency. Size and how fast it is growing are what doctors watch most closely.

Definition

The aortic valve is the one-way gate between the heart's main pumping chamber and the aorta.

Why it matters

It can narrow with age as calcium builds up on it, or leak. Elevated Lp(a) is one of the few known risk factors for the narrowing, connecting valve disease to the same particle biology as plaque.

Definition

ApoB is a protein that sits on the outside of every cholesterol particle that can get stuck in your artery wall and cause plaque. Each of those particles carries exactly one ApoB.

Why it matters

That one-to-one rule is what makes it so useful. Measuring ApoB counts the particles. A standard cholesterol test measures the cargo inside the particles instead, which can be misleading if your particles are unusually empty or full.

Definition

Discordance is when your ApoB and your LDL cholesterol tell two different stories. Your LDL looks fine, but your particle count is high — or the reverse.

Why it matters

It happens when your particles are carrying less cholesterol than usual, so it takes more of them to add up to the same number on the lab report. It is especially common in people with insulin resistance or diabetes. When the two disagree, ApoB is the one that tracks your actual risk.

Definition

APOC3 is the gene for a protein that blocks the clearance of triglyceride-rich particles from your blood.

Why it matters

Less of it means faster clearance. People carrying a naturally broken copy have lower triglycerides and fewer heart attacks, which is strong evidence that these particles are causing harm rather than just tagging along.

Definition

APOE is a gene that comes in three common versions, labeled E2, E3, and E4. It controls how efficiently your liver clears leftover fat particles.

Why it matters

The E4 version raises both cholesterol and Alzheimer's risk, which is one of the threads connecting heart disease and brain disease. Knowing your type does not change treatment much, but it can explain an otherwise puzzling lipid pattern.

Definition

An apolipoprotein is a protein attached to a fat-carrying particle in your blood. Fat and water don't mix, so these proteins act like a wrapper that lets fat travel safely through the bloodstream.

Why it matters

Different wrappers mark different kinds of particles. ApoB marks the harmful ones. ApoA-I marks HDL. Knowing which wrapper you are measuring tells you which particles you are counting.

Definition

Apolipoprotein A-I is the main structural protein of HDL particles, roughly the HDL equivalent of what ApoB is for the harmful ones.

Why it matters

It carries out the actual work of collecting cholesterol from cells. Measuring it gives a slightly better picture of HDL function than the cholesterol number alone, though neither has proven useful as a treatment target.

Definition

ARIC, the Atherosclerosis Risk in Communities study, has followed thousands of American adults since the late 1980s.

Why it matters

Decades of follow-up let researchers watch risk factors measured in middle age play out into actual events much later. It is one of the studies behind the idea that exposure over time, not a single reading, is what counts.

Definition

Remodeling is the way an artery changes shape as plaque builds up. Often the artery bulges outward to make room, keeping the opening in the middle wide enough for blood to pass.

Why it matters

This is why heart disease can hide for decades. The artery is quietly filling with plaque, but because it expanded outward, tests that only look at the opening say everything is fine.

Definition

An artery is a blood vessel that carries blood away from the heart to the rest of the body.

Why it matters

Artery walls have layers. Plaque does not build up inside the open channel like gunk in a pipe — it builds up inside the wall itself. That difference explains a lot about why heart disease is so easy to miss.

Definition

Aspirin makes blood platelets less sticky, so clots are less likely to form.

Why it matters

If you have already had a heart attack or stroke, daily aspirin usually helps. If you have not, the picture changed: newer studies found the bleeding risk roughly cancels out the benefit for most healthy adults. This is one of the clearest examples of medical advice reversing based on better evidence.

Definition

ASTEROID was a trial that gave patients the highest dose of rosuvastatin and photographed their coronary plaque with intravascular ultrasound before and after.

Why it matters

It showed measurable plaque shrinkage — one of the first clear demonstrations that very low LDL can reverse disease, not merely halt it.

Definition

Atherogenesis is the step-by-step process of a plaque forming.

Why it matters

It starts when an ApoB particle slips into the artery wall and gets trapped. The body treats it as an invader and sends in immune cells. Those cells eat the trapped cholesterol, get stuck themselves, and die there. Repeat this for twenty years and you have a plaque.

Definition

Atheroma is another word for the fatty deposit inside an artery wall — essentially a synonym for plaque, used more often in research writing.

Why it matters

The root gives us "atherosclerosis." It comes from a Greek word for gruel, describing what the soft core of a plaque actually looks like.

Definition

Atherosclerosis is the disease behind most heart attacks and many strokes. Cholesterol particles get stuck in the wall of an artery, the body sends immune cells to clean up, and over years that mess hardens into plaque.

Why it matters

The key thing to understand is that it starts young — often in the teens and twenties — and grows silently for decades before anyone notices. By the time it causes a symptom, it has usually been building for most of your life.

Definition

Athlete's heart describes the normal changes that happen to a heart trained hard for years. The walls thicken a bit, the chambers get bigger, and the resting pulse drops.

Why it matters

These changes are healthy adaptations, not disease. The complication is that they can look similar to real heart problems on a test, so they need to be read by someone who understands athletes.

Definition

Atorvastatin, sold as Lipitor, is one of the two strongest statins and among the most prescribed medicines in the world.

Why it matters

At high dose it typically lowers LDL by around half. It is inexpensive, generic, and backed by more outcome evidence than almost any other drug in medicine.

Definition

Atrial fibrillation, often shortened to AFib, is a fast and irregular heartbeat that starts in the upper chambers of the heart.

Why it matters

Because those chambers quiver instead of squeezing properly, blood can pool and form a clot, which may travel to the brain and cause a stroke. Interestingly, endurance athletes get AFib more often than couch potatoes — one of the few ways heavy exercise raises a risk instead of lowering it.

Definition

An automated external defibrillator, or AED, is a portable device that can shock a stopped heart back into rhythm. It talks you through what to do, and it will not deliver a shock unless one is needed.

Why it matters

When someone collapses from cardiac arrest, survival drops with every passing minute. A bystander with an AED nearby saves far more lives than waiting for an ambulance.

Definition

Belly fat that sits deep in the abdomen, wrapped around the organs, is called visceral fat. It is different from the softer fat you can pinch under the skin.

Why it matters

Visceral fat is active. It sends out chemical signals that raise blood sugar, blood pressure, and triglycerides. This is why waist size can predict heart trouble better than weight on the scale.

Definition

Bempedoic acid is a cholesterol-lowering pill that works in the liver, at a point just before where statins act.

Why it matters

Its main advantage is that it stays out of muscle tissue, so it rarely causes the muscle aches some people get from statins. That makes it a useful option for people who truly cannot tolerate a statin.

Definition

A beta blocker is a medicine that slows the heart and makes it beat less forcefully, which lowers blood pressure and reduces how much oxygen the heart needs.

Why it matters

Common examples include metoprolol and carvedilol. They are widely used after heart attacks and in heart failure, where a calmer, slower heart is easier on damaged muscle.

Definition

A bicuspid aortic valve has two flaps instead of the usual three. It is present from birth in roughly one person in a hundred.

Why it matters

It is the most common heart abnormality people are born with. It tends to narrow earlier in life and often comes with a wider aorta, so both need periodic monitoring.

Definition

Bile acids are made by your liver from cholesterol and released into the gut to help digest fat.

Why it matters

This is the body's main route for disposing of cholesterol. Soluble fiber works by binding bile acids so they leave the body instead of being reabsorbed, forcing the liver to pull more cholesterol from the blood.

Definition

A biomarker is something measurable in the body that tells you about health or disease — a lab value, a scan result, a blood pressure reading.

Why it matters

The catch is that changing a biomarker does not automatically mean you have changed your fate. A number can improve while the underlying disease keeps going. Good biomarkers are ones that have been proven to track real outcomes.

Definition

A blood clot is a clump of blood cells and protein that forms to stop bleeding.

Why it matters

Clots are lifesaving when you cut yourself. They are dangerous when they form inside an artery. Most heart attacks happen when a plaque cracks open and a clot forms on top of it, suddenly shutting off blood flow.

Definition

Blood pressure is the force of blood pushing against your artery walls. It is written as two numbers, like 120/80. The top number is the pressure when your heart squeezes, the bottom is when it relaxes.

Why it matters

High blood pressure damages artery walls over time and makes it easier for cholesterol particles to get in. It usually causes no symptoms at all, which is why it gets missed for years.

Definition

Blood sugar, or glucose, is the fuel your cells run on. Your body works hard to keep it in a narrow range.

Why it matters

When it stays high for years, it damages blood vessels throughout the body — including the ones feeding your heart, kidneys, eyes, and nerves. High blood sugar often shows up alongside high triglycerides and a high particle count.

Definition

Body mass index, or BMI, is a number calculated from your height and weight, used as a rough measure of body size.

Why it matters

It is convenient but crude. It cannot tell muscle from fat, and it says nothing about where your fat is stored. A muscular athlete can land in the overweight range while being perfectly healthy, and a thin person can carry dangerous visceral fat.

Definition

The Bogalusa Heart Study examined the arteries of children and young adults who died in accidents in a Louisiana town.

Why it matters

The findings were startling: fatty streaks and early plaque in teenagers, and more of it in those with higher cholesterol and blood pressure. It is direct evidence that heart disease begins decades before anyone feels anything.

Definition

Bypass surgery takes a healthy blood vessel from somewhere else in your body and uses it to route blood around a badly blocked coronary artery.

Why it matters

Like a stent, it restores blood flow to muscle that was starving. Also like a stent, it treats one location. The disease process continues in the rest of your arteries unless the underlying causes are addressed.

Definition

C-reactive protein, or CRP, is a substance your liver makes when there is inflammation somewhere in your body. A sensitive version of the test, hs-CRP, is used to estimate heart risk.

Why it matters

A high result means inflammation, but not where it is coming from — a cold, arthritis, or gum disease will raise it too. It adds information but does not replace measuring your particle count.

Definition

Calcification is when calcium gets deposited into a plaque, turning part of it hard and bony.

Why it matters

It sounds bad, and a high total amount does signal a lot of disease. But the hardening itself is partly the body's repair job — a hard, stable plaque is less likely to crack open than a soft, greasy one. This is why statins and heavy exercise can both make plaque look more calcified while making it safer.

Definition

Calcified plaque is the hardened, calcium-filled part of a plaque. It shows up brightly on a CT scan, which is what a calcium scan measures.

Why it matters

Athletes often have more calcified plaque than non-athletes, but it tends to be the dense, stable kind. The amount and the type both matter, not just the total number.

Definition

Carbohydrates are the sugars and starches in food — bread, rice, pasta, fruit, potatoes, sweets.

Why it matters

Quality matters more than quantity for most people. Whole grains, beans, and vegetables behave very differently in the body than white flour and sugar, even though they are all technically carbohydrates.

Definition

CARDIA has followed young adults from their twenties into later life, tracking fitness, cholesterol, blood pressure, and what eventually happened to them.

Why it matters

Because it started so early, it captured the years when plaque is silently forming. It supplies much of the evidence that risk factors in your twenties shape your arteries in your fifties.

Definition

Cardiac arrest is when the heart suddenly stops pumping and the person collapses, stops breathing normally, and loses consciousness within seconds.

Why it matters

It is not the same as a heart attack. A heart attack is a plumbing problem — blocked blood flow. Cardiac arrest is an electrical problem — the heart's rhythm falls apart. A heart attack can trigger one, but so can other things. Without CPR and a defibrillator, survival drops fast.

Definition

Cardiac catheterization is a procedure where a thin tube is threaded through a blood vessel, usually from the wrist or groin, up into the heart's arteries.

Why it matters

Doctors use it to see blockages, measure pressures, and often to place a stent in the same session. It is how many people first learn how much disease they actually have.

Definition

Cardiac MRI uses magnetic fields rather than X-rays to image the heart in fine detail, with no radiation.

Why it matters

It is the best test for scarring in the heart muscle, which makes it valuable for distinguishing an athlete's healthy enlarged heart from genuine disease.

Definition

Cardiomyopathy is disease of the heart muscle itself, rather than of the arteries feeding it.

Why it matters

The muscle may thicken, stretch, or stiffen. Several forms are inherited, and they are among the leading causes of sudden death in young athletes — a different problem entirely from plaque.

Definition

Cardiorespiratory fitness is how well your heart, lungs, and muscles work together to use oxygen during hard exercise. It is often measured as VO2 max.

Why it matters

It is one of the strongest predictors of how long you will live — stronger than most lab values. But being extremely fit does not make you immune to plaque, which is a hard lesson many endurance athletes have learned.

Definition

Cardiovascular disease is the umbrella term for problems with the heart and blood vessels, including heart attacks, strokes, and blocked leg arteries.

Why it matters

It is the leading cause of death worldwide. Most of it traces back to the same underlying process: plaque slowly building in artery walls over decades.

Definition

Carnitine is a nutrient found mostly in red meat. Your body also makes some on its own.

Why it matters

It matters here because gut bacteria can convert carnitine into a compound called TMAO, which has been linked to heart disease. How strong that link really is remains debated.

Definition

The carotid arteries run up either side of your neck and supply blood to your brain.

Why it matters

They are easy to scan with ultrasound, so researchers often use them to study plaque without needing to look at the heart directly. Plaque in a carotid artery can break loose and cause a stroke.

Definition

A case-control study starts with people who already have a disease, finds similar people who do not, and looks backward for differences.

Why it matters

It is efficient for rare conditions. Its weakness is that it relies on recall and records from the past, and people who are ill tend to remember their history differently.

Definition

Causation means one thing actually makes another thing happen. It is different from correlation, which only means two things tend to show up together.

Why it matters

This distinction runs through almost every health headline you read. Wine drinkers were healthier — but the wine was not the reason. Sorting real causes from tag-alongs is most of the work in medical research.

Definition

CETP is a protein that swaps cholesterol and triglycerides between HDL and the harmful ApoB particles.

Why it matters

Blocking it raises HDL dramatically, so drug companies spent billions trying. Most of those drugs failed to prevent heart attacks, and one caused harm. It became the clearest evidence that raising HDL is not itself a treatment.

Definition

Cholesterol is a waxy substance your body needs. It goes into cell walls, hormones, vitamin D, and the bile that digests your food. You would die without it.

Why it matters

The problem is not cholesterol existing. The problem is how much of it is riding around in your bloodstream inside particles that can burrow into artery walls.

Definition

When cholesterol accumulates past what a plaque can hold in solution, it crystallizes into sharp needle-like structures.

Why it matters

These crystals physically damage immune cells and trip the NLRP3 alarm, producing a burst of inflammation. They can also puncture a fibrous cap from the inside.

Definition

Cholesterol efflux capacity is a laboratory test of how well someone's HDL actually pulls cholesterol out of cells — a measure of function rather than quantity.

Why it matters

It predicts risk better than the HDL number does, which supports the view that HDL quality is what matters. It remains a research test, not something you can order routinely.

Definition

Cholesterol synthesis is your body making its own cholesterol, mostly in the liver. Almost every cell can do it.

Why it matters

This is why cutting cholesterol out of your food does less than people expect — when you eat less, your body simply makes more. It is also why statins work: they slow the factory rather than blocking the food.

Definition

See CETP for the full entry.

Definition

Choline is a nutrient found in eggs, red meat, and liver. Your body genuinely needs it, especially for the brain.

Why it matters

Like carnitine, it can be converted by gut bacteria into TMAO. This is the biological chain that connects certain foods to a possible heart risk through the gut microbiome.

Definition

Chronic kidney disease is a lasting reduction in the kidneys' ability to filter waste from the blood.

Why it matters

It raises cardiovascular risk independently and steeply — many people with kidney disease die of heart disease before their kidneys fail. It also alters calcium handling in blood vessels.

Definition

A chylomicron is a very large particle that carries fat from a meal out of your intestines and into your bloodstream.

Why it matters

Whole chylomicrons are too big to squeeze into an artery wall, so they are not directly dangerous. But as they shrink and drop off their cargo, the leftovers — called remnants — are small enough to get in and cause trouble.

Definition

A clinical trial is a study where researchers give one group a treatment and another group a placebo or standard care, then compare what happens.

Why it matters

When people are assigned randomly, it is the most reliable way we have to find out if something truly works. Observational studies can only watch what people already do, which leaves room for other explanations.

Definition

Coconut oil is a cooking fat that got marketed as a superfood despite being very high in saturated fat.

Why it matters

Studies consistently show it raises LDL cholesterol, similar to butter. The health-food reputation came from marketing and a few misread studies, not from evidence that it protects your heart.

Definition

A cohort study follows a large group of people over time, recording what they eat or do and what happens to their health years later.

Why it matters

These studies are valuable for spotting patterns, but they cannot prove cause. People who choose a habit usually differ in other ways too, and those differences can be the real explanation.

Definition

Colchicine is an old, cheap anti-inflammatory drug, used for centuries in gout, now repurposed for heart disease.

Why it matters

It reduces events in people who keep having them despite well-controlled cholesterol. It is the most practical evidence so far that treating inflammation directly adds something.

Definition

Collateral circulation is a network of small backup blood vessels that can grow around a blocked artery, like a detour around a closed road.

Why it matters

People who develop good collaterals sometimes survive blockages that would otherwise be devastating. Long-term exercise appears to encourage them, which may be one reason very fit people can have severe disease without symptoms.

Definition

A composite endpoint bundles several different outcomes together and counts whichever happens first.

Why it matters

Bundling makes trials smaller and faster. It can also mislead, because a headline reduction may be driven entirely by the least serious component — more procedures avoided rather than fewer deaths.

Definition

Computed tomography, or CT, takes X-ray images from many angles and reconstructs them into cross-sections of the body.

Why it matters

It is the technology behind both the calcium scan and CT angiography — the two tests that let doctors see coronary plaque without threading a catheter into an artery.

Definition

A confidence interval is the range of values that are statistically compatible with what a study found.

Why it matters

It shows how solid a result is. A narrow interval means a precise finding; a wide one that crosses "no effect" means the study could not really tell whether the treatment worked.

Definition

Confounding is when a hidden third factor makes two unrelated things look connected.

Why it matters

Classic example: people who take vitamins are healthier. But they also exercise more, smoke less, and see doctors more often. The vitamin gets credit for what those other habits did. Untangling confounding is why good studies are so hard to run.

Definition

A very large Danish study that measured lipids, including Lp(a) and remnant cholesterol, in tens of thousands of people and followed their health for years.

Why it matters

Denmark's national health records make follow-up unusually complete. Much of what we know about remnant cholesterol and Lp(a) as independent risks comes from this dataset.

Definition

CORDIOPREV compared a Mediterranean diet against a low-fat diet in people who already had coronary disease, following them for seven years.

Why it matters

It is one of the few long, well-run dietary trials in people with established disease, and it reported fewer events on the Mediterranean pattern.

Definition

The coronary arteries are the small vessels that wrap around the outside of your heart and feed the heart muscle itself.

Why it matters

They are surprisingly small — roughly the width of a coffee stirrer. When one gets blocked, the muscle it feeds starts to die within minutes.

Definition

A coronary artery calcium score, or CAC score, comes from a quick CT scan that measures how much hardened plaque is in your heart's arteries. No dye, no needles, about ten minutes.

Why it matters

A score of zero is genuinely reassuring for most middle-aged people. A high score means real disease is present, even if you feel perfectly fine. It is one of the few tests that can show you your disease instead of just estimating your odds.

Definition

Coronary artery disease is plaque buildup in the arteries feeding the heart muscle.

Why it matters

It is the most common form of heart disease and the usual cause of heart attacks. It builds silently for decades, which is why the first symptom for many people is also a serious event.

Definition

Coronary CT angiography, or CCTA, is a CT scan done with dye in your veins that produces detailed pictures of your heart's arteries.

Why it matters

Unlike a calcium scan, it can see soft plaque as well as hard plaque, and unlike an invasive angiogram it requires no catheter. It shows both how narrow an artery is and what the plaque is made of.

Definition

Coronary flow reserve compares blood flow through the heart's arteries at rest with flow when the heart is working hard.

Why it matters

A poor result with clear large arteries points to trouble in the tiny vessels instead — a real and often missed cause of chest pain, especially in women.

Definition

A cross-sectional study takes a single snapshot of a population at one moment.

Why it matters

It can show that two things occur together but never which came first. Studies of this kind are frequently reported as if they showed cause, and they cannot.

Definition

The Cholesterol Treatment Trialists' Collaboration pools the raw data from every major statin trial rather than just comparing published summaries.

Why it matters

With hundreds of thousands of patients, it produced the central finding of modern lipid care: each unit of LDL reduction buys a roughly proportional reduction in events, no matter how you achieve it.

Definition

Cumulative exposure is the total amount of harmful cholesterol particles your arteries have been soaked in across your entire life — how high, multiplied by how long.

Why it matters

This is the single most important idea on this site. Someone with a moderately high level since age 20 can end up with more damage than someone with a very high level starting at 55. Plaque adds up. Starting earlier matters more than starting harder.

Definition

Curing a disease means stopping the process that causes it. Reversing means undoing damage that has already been done. They are not the same thing.

Why it matters

With heart disease you can stop the process almost completely by driving particle levels low enough. Undoing the existing plaque is slower and only partial. Being clear about which one is being promised matters a great deal when reading health claims.

Definition

De novo lipogenesis is your liver manufacturing fat from scratch, mostly out of excess carbohydrate.

Why it matters

It is how a very high sugar or refined starch intake ends up raising triglycerides and depositing fat in the liver, even when you are not eating much fat.

Definition

Diabetes is a condition where blood sugar stays too high, either because the body makes too little insulin or because it stops responding to the insulin it makes.

Why it matters

It roughly doubles heart disease risk. Part of that is the sugar damaging blood vessels, and part is that diabetes usually comes bundled with high triglycerides and a high particle count that a standard cholesterol test can miss.

Definition

Diastolic blood pressure is the bottom number in a blood pressure reading. It is the pressure in your arteries while the heart is relaxing between beats.

Why it matters

In younger adults it is often the more meaningful of the two numbers. In older adults, the top number usually matters more because arteries have stiffened.

Definition

Dietary cholesterol is the cholesterol in food — eggs, shrimp, liver, and other animal products.

Why it matters

For most people it has a surprisingly small effect on blood cholesterol, because the body compensates by making less. Saturated fat in food generally raises blood cholesterol more than cholesterol in food does. This is why egg advice kept flip-flopping for decades.

Definition

See ApoB Discordance for the full entry.

Definition

A dose-response relationship means more of something produces more of an effect, in a consistent gradient.

Why it matters

It is one of the classic signs that a relationship is causal rather than coincidental. LDL and heart disease show it clearly: the higher and the longer, the more plaque.

Definition

Dyslipidemia is the medical word for an unhealthy pattern of fats in the blood. It can mean high LDL, high triglycerides, low HDL, or some combination.

Why it matters

The word describes a pattern rather than one number, which is why treatment depends on which part is off and why.

Definition

An echocardiogram is an ultrasound picture of your heart. A technician moves a probe across your chest and sound waves build a moving image of the chambers and valves.

Why it matters

It shows how well the heart is pumping and whether the valves are working. It does not show plaque in the coronary arteries, so a normal echo does not mean your arteries are clear.

Definition

Efferocytosis is the housekeeping process by which immune cells clear away other cells that have died.

Why it matters

Inside a plaque this cleanup fails. Dead foam cells pile up instead of being removed, and that debris becomes the necrotic core. Restoring the cleanup is an active area of drug research.

Definition

Ejection fraction is the percentage of blood the main pumping chamber squeezes out with each beat. A normal value is somewhere around 55 to 70 percent.

Why it matters

A low number means the heart is not pumping strongly, often after a heart attack or from long-standing high blood pressure.

Definition

An electrocardiogram — ECG or EKG — records your heart's electrical activity through stickers placed on your skin. It takes about a minute and is painless.

Why it matters

It can reveal rhythm problems, signs of a current or past heart attack, and some inherited electrical conditions that put young athletes at risk. It is a normal-looking test in many people who still have significant plaque.

Definition

An emergency action plan is a written, practiced plan for what happens if someone collapses at a school, gym, or sporting event: who calls 911, who starts CPR, and who runs for the defibrillator.

Why it matters

Places with a rehearsed plan save dramatically more lives than places that simply own a defibrillator. Having the equipment is not the same as knowing what to do with it.

Definition

Endothelial dysfunction is when that thin lining stops doing its job well. Vessels don't widen properly, and the barrier gets leakier.

Why it matters

It is one of the earliest changes in heart disease, showing up long before any plaque is visible on a scan. Smoking, high blood pressure, high blood sugar, and high particle counts all damage it.

Definition

The endothelium is the ultra-thin, slippery lining on the inside of every blood vessel. It is only one cell thick.

Why it matters

It is far more than a coating. It controls how much your vessels relax or tighten, keeps blood from clotting where it shouldn't, and decides what gets through into the wall. When it stops working properly, cholesterol particles slip in more easily.

Definition

Epidemiology is the study of health patterns in large groups of people — who gets sick, where, and what they had in common.

Why it matters

It generates most of the diet headlines you see. It is genuinely useful for spotting clues, but on its own it cannot prove that one thing caused another.

Definition

Estrogen is a hormone, present at much higher levels in women before menopause, that affects blood vessels, cholesterol, and bone.

Why it matters

It appears to offer some protection to arteries, which is part of why women tend to develop heart disease about ten years later than men. What happens when estrogen drops at menopause, and whether replacing it helps, is more complicated than it was once made to sound.

Definition

Evinacumab is an injectable antibody that blocks ANGPTL3, used for the most severe inherited cholesterol disorders.

Why it matters

It works even in patients whose LDL receptors barely function, because it lowers cholesterol by a route that does not depend on them. For children with the homozygous form, that distinction is life-changing.

Definition

Evolocumab is an injectable cholesterol medicine in the PCSK9 inhibitor family, usually given every two to four weeks.

Why it matters

It works by protecting the liver's cholesterol-removing receptors, and it can cut LDL and ApoB by half or more even in people already on a statin.

Definition

The extracellular matrix is the scaffolding of collagen and other fibers that holds tissue together and gives an artery wall its strength.

Why it matters

It is what a fibrous cap is made of. When inflammatory enzymes break it down faster than cells rebuild it, the cap thins and the plaque becomes fragile.

Definition

Ezetimibe is a pill that blocks your intestines from absorbing cholesterol.

Why it matters

On its own it lowers cholesterol modestly. Its real value is as a partner drug — added to a statin, it pushes levels lower without increasing the statin dose, and it very rarely causes side effects.

Definition

Familial hypercholesterolemia, or FH, is an inherited condition where the liver cannot clear cholesterol from the blood properly. Levels are very high from birth.

Why it matters

Roughly one in 250 people has it, and most of them don't know. Because the exposure starts in childhood, heart attacks can happen in a person's thirties or forties. It is one of the strongest arguments for checking cholesterol early rather than waiting for middle age.

Definition

Family history means whether your close relatives developed heart disease, and how young they were when it happened.

Why it matters

Early disease in a parent or sibling — before about 55 in men or 65 in women — is a meaningful warning sign. It can reflect shared genes, shared habits, or both, and it should push you toward testing sooner rather than later.

Definition

Fatty liver is fat accumulating inside liver cells, now usually called metabolic dysfunction-associated steatotic liver disease.

Why it matters

It is extremely common, usually silent, and closely tied to insulin resistance. A fatty liver also produces more ApoB particles, so it raises cardiovascular risk as well as liver risk.

Definition

A fatty streak is the earliest visible stage of atherosclerosis — a flat yellow smear of cholesterol-filled immune cells just under the artery lining.

Why it matters

They appear in childhood and are present in most teenagers. Not all become plaques, but they are where the process starts, which is why prevention is increasingly discussed as a lifelong matter.

Definition

Fiber is the part of plant food your body cannot digest. It is found in beans, oats, vegetables, fruit, and whole grains.

Why it matters

Soluble fiber grabs onto bile in your gut and carries it out, which forces your liver to pull cholesterol from your blood to make more. That is a genuine cholesterol-lowering effect from food, not just a general healthy-eating claim.

Definition

Fibrates are pills that lower triglycerides by making the body break down fat-carrying particles more quickly.

Why it matters

They reliably improve the numbers. Whether they prevent heart attacks is much less clear, and most trials have been disappointing except possibly in people with very high triglycerides and low HDL.

Definition

The fibrous cap is the tough layer of tissue covering a plaque, separating its greasy core from the bloodstream.

Why it matters

Think of it as a lid. A thick lid holds. A thin one can tear, and when it does, a clot forms on the spot and a heart attack follows. Much of what cholesterol medicine does is make that lid thicker.

Definition

A foam cell is an immune cell that has eaten so much trapped cholesterol that it swells up and looks foamy under a microscope.

Why it matters

These cells came to help, then got stuck and died where they sat. Piles of dead foam cells form the greasy center of a plaque. They are the reason plaque is as much an immune problem as a fat problem.

Definition

FOURIER tested evolocumab, a PCSK9 inhibitor, in patients who already had cardiovascular disease and were on statins.

Why it matters

It drove LDL down to around 30 mg/dL and still reduced events, with no sign of a floor below which lowering stopped helping. It largely settled the question of whether very low LDL is safe.

Definition

Fractional flow reserve measures the pressure drop across a narrowing to find out whether it is actually restricting blood flow.

Why it matters

Eyeballing an angiogram is unreliable. A lesion that looks tight may pass plenty of blood, and stenting one that does not need it provides no benefit. This test decides which narrowings are worth treating.

Definition

The Framingham Heart Study began in 1948 in one Massachusetts town and has now followed three generations of families.

Why it matters

It gave us the phrase "risk factor" and identified cholesterol, blood pressure, and smoking as the drivers of heart disease. Nearly every risk calculator descends from it.

Definition

Free fatty acids are fat molecules travelling loose in the blood after being released from fat stores.

Why it matters

Visceral fat dumps them straight into the vein feeding the liver. The liver responds by making more triglycerides and more ApoB particles — the mechanical link between belly fat and a bad lipid panel.

Definition

A gene variant is a small difference in your DNA compared with most other people.

Why it matters

Some variants raise cholesterol, some lower it, and some barely matter. Studying people who were born with naturally low cholesterol has been one of the most powerful ways to prove that lowering it actually prevents heart attacks.

Definition

Genetics is the study of what you inherit from your parents.

Why it matters

Your genes strongly influence your cholesterol, blood pressure, and how early plaque starts forming. What they do not do is seal your fate. Genes set your starting point and how fast the meter runs; what you do about it still changes the outcome.

Definition

Gestational diabetes is high blood sugar that appears during pregnancy and usually resolves after delivery.

Why it matters

Resolving is not the end of it. It signals a metabolism that struggles under load, and it strongly predicts later type 2 diabetes and cardiovascular disease.

Definition

GLAGOV added a PCSK9 inhibitor to statin therapy and measured coronary plaque with intravascular ultrasound before and after.

Why it matters

Plaque shrank, and it shrank even in patients whose starting LDL was already considered good. It is a key piece of evidence that lower is better for reversing disease, not just slowing it.

Definition

GLP-1 receptor agonists are injectable medicines — semaglutide and tirzepatide are the best known — that copy a gut hormone controlling appetite and blood sugar.

Why it matters

They cause substantial weight loss, but the interesting finding is that they reduce heart attacks and strokes faster than the weight comes off. That suggests they are doing something to blood vessels directly, not just shrinking waistlines.

Definition

Glucose is the sugar your blood carries to fuel your cells.

Why it matters

Your body keeps it in a tight range using insulin. When that system starts failing, glucose creeps up — and the damage to blood vessels begins well before the number is high enough to be called diabetes.

Definition

Glycemic control is how steadily your blood sugar is kept in a healthy range over time.

Why it matters

Good control clearly protects the small vessels of the eyes, kidneys, and nerves. Its effect on heart attacks is weaker, which is why cholesterol and blood pressure still need treating in their own right.

Definition

The glycocalyx is a delicate sugar-rich coating on the inner surface of blood vessels, a kind of gel layer between the blood and the cells.

Why it matters

It acts as a first barrier and helps the vessel sense blood flow. Damage to it — from high blood sugar, inflammation, or turbulent flow — is one of the earliest events in vascular disease.

Definition

The gut microbiome is the enormous community of bacteria living in your intestines. There are trillions of them, and they are not passive passengers.

Why it matters

They break down parts of your food into new compounds that enter your bloodstream. That means what you eat can affect your heart indirectly, through what your bacteria make out of it.

Definition

A hazard ratio compares how quickly events happen in two groups. A ratio of 0.75 means events occurred at three-quarters the rate in the treated group.

Why it matters

It is a relative measure, so it says nothing about how common the event was to begin with. A hazard ratio of 0.5 sounds dramatic whether the risk fell from 40 percent to 20 or from 0.4 percent to 0.2.

Definition

HDL, or high-density lipoprotein, is the particle often called "good cholesterol." It picks up cholesterol from tissues and carries it back to the liver.

Why it matters

The nickname has aged badly. People with naturally high HDL are healthier, but drugs that raise HDL have repeatedly failed to prevent heart attacks. High HDL seems to be a sign of good health rather than a cause of it.

Definition

A heart attack happens when blood flow to part of the heart muscle is cut off and that muscle starts to die.

Why it matters

The usual trigger is not a slow closing of the artery. It is a plaque cracking open, with a clot forming on top in minutes. That is why heart attacks so often strike people who felt fine the day before, and why plaques too small to cause symptoms can still kill.

Definition

Heart failure means the heart cannot pump well enough to meet the body's needs. The name is misleading — it does not mean the heart has stopped.

Why it matters

It causes breathlessness, swollen legs, and fatigue. Common causes include past heart attacks, long-standing high blood pressure, and valve problems.

Definition

Heart rate is how many times your heart beats per minute.

Why it matters

A lower resting rate usually reflects better fitness — trained endurance athletes often sit in the 40s. On its own, though, resting heart rate says very little about whether you have plaque.

Definition

Hemoglobin A1c is a blood test showing your average blood sugar over the past two to three months, rather than at one moment.

Why it matters

Because it averages, it catches problems a single fasting test can miss. It is the standard way diabetes and prediabetes are diagnosed and tracked.

Definition

A high-intensity statin is a dose expected to cut LDL by 50 percent or more — in practice, higher doses of atorvastatin or rosuvastatin.

Why it matters

Guidelines call for this level after a heart attack or in very high-risk patients, rather than starting low and slowly working up. The size of the reduction is what drives the benefit.

Definition

HMGCR is the gene for HMG-CoA reductase, the enzyme that performs the rate-limiting step in making cholesterol. It is the exact target of every statin.

Why it matters

People born with a naturally less active version have lower cholesterol and fewer heart attacks — essentially a lifelong, low-dose statin from birth. That genetic evidence is why statins are trusted as causal, not just correlated.

Definition

Homozygous familial hypercholesterolemia, or HoFH, is the rare and severe form of inherited high cholesterol, where a child inherits the faulty gene from both parents instead of one.

Why it matters

Cholesterol levels can be four to eight times normal from birth. Without aggressive treatment, these children can develop the arteries of a 60-year-old before they finish school. It is the most extreme demonstration of what lifelong cholesterol exposure does.

Definition

Hormone replacement therapy, or HRT, gives estrogen — sometimes with progesterone — to women whose levels dropped at menopause.

Why it matters

The story here has swung wildly. Early studies suggested it protected the heart, a large trial then suggested harm, and closer analysis showed that timing and delivery method matter enormously. Starting near menopause with a patch looks very different from starting fifteen years later with a pill.

Definition

HUYGENS used optical coherence tomography — a very high-resolution imaging catheter — to see whether a PCSK9 inhibitor changed plaque structure after a heart attack.

Why it matters

Fibrous caps got thicker and lipid cores got smaller. It is direct visual evidence for plaque stabilization, not just a change in a lab number.

Definition

Hypertension is the medical term for high blood pressure.

Why it matters

It damages artery walls year after year without causing any symptoms, which is how it earned the nickname "silent killer." Along with cholesterol particles and smoking, it is one of the main forces driving plaque growth.

Definition

Hypertrophic cardiomyopathy is an inherited condition in which the heart muscle grows abnormally thick.

Why it matters

It is a leading cause of sudden cardiac death in young athletes. The difficulty is that a trained heart is also thicker than average, so telling healthy adaptation from disease takes careful specialist assessment.

Definition

ICAM-1 is a molecule that appears on the surface of the blood vessel lining and acts like Velcro, catching passing immune cells.

Why it matters

It is one of the first visible signs that an artery wall has turned inflamed and started recruiting the cells that will eventually build a plaque.

Definition

Icosapent ethyl is a purified, high-dose form of the omega-3 fat EPA, sold as Vascepa.

Why it matters

Unlike ordinary fish oil it reduced events in a major trial. The result is debated, because the placebo used may itself have been harmful, and other purified omega-3 trials have been negative.

Definition

IDL, or intermediate-density lipoprotein, is a particle that forms partway through the process of a big triglyceride-carrying particle shrinking down into an LDL particle.

Why it matters

It carries ApoB, so it can lodge in artery walls just like LDL can. A standard cholesterol panel does not list it separately, which is one more reason the standard panel undercounts your real risk.

Definition

Interleukin-6, or IL-6, is a signaling molecule the immune system uses to spread an inflammatory message through the body.

Why it matters

It sits upstream of C-reactive protein, which is why CRP rises when IL-6 does. Blocking this pathway is one of the main strategies being tested for reducing inflammatory risk that persists after cholesterol is controlled.

Definition

IMPROVE-IT added ezetimibe to a statin after a heart attack, testing whether lowering LDL by a non-statin mechanism would help.

Why it matters

It did. That mattered enormously, because it showed the benefit comes from the lower LDL itself rather than from something special about statins.

Definition

Inclisiran is a cholesterol-lowering injection given just twice a year after the first two doses.

Why it matters

Instead of blocking a protein the way other drugs do, it tells the liver to stop making that protein in the first place. Twice-yearly dosing solves the biggest weakness of daily pills, which is that people forget to take them.

Definition

Inflammation is your immune system's response to injury or something it treats as an invader. It brings swelling, heat, and cleanup cells.

Why it matters

In arteries, inflammation starts because cholesterol particles got trapped in the wall. It then makes everything worse — thinning the plaque's protective cap and enlarging its greasy core. It is a powerful accelerator, but it is not the spark.

Definition

Insulin is a hormone made by your pancreas. Its main job is letting sugar move out of your blood and into your cells for fuel.

Why it matters

You cannot live without it. Trouble starts either when your body stops making enough of it, or when your cells stop listening to it.

Definition

Insulin resistance is when your cells stop responding well to insulin, so your pancreas has to pump out more and more to do the same job.

Why it matters

It usually shows up years before blood sugar rises enough to be called diabetes. It also scrambles your cholesterol particles — making them smaller and more numerous — so your LDL number can look fine while your actual particle count is high.

Definition

Insulin sensitivity is how well your cells respond to insulin. It is the opposite of insulin resistance.

Why it matters

Better sensitivity means lower insulin levels, better blood sugar, and lower triglycerides. Exercise improves it within a single session, which is one reason activity helps even before any weight is lost.

Definition

The intima is the innermost layer of an artery wall, sitting just beneath the smooth lining.

Why it matters

This is where plaque actually forms. Not in the open channel where blood flows — inside the wall itself. Getting this straight changes how you picture the whole disease.

Definition

Intima-media thickness, or IMT, is a measurement of how thick the inner layers of an artery have become, usually taken in the neck with ultrasound.

Why it matters

Researchers like it because it is easy and harmless to measure repeatedly. Just be careful reading claims about it: a thinner measurement in a study is not the same thing as plaque shrinking in your heart.

Definition

Intraplaque hemorrhage is bleeding inside a plaque, from the fragile little vessels that grew into it.

Why it matters

Blood spilled inside a plaque dumps cholesterol-rich membrane straight into the core, and the plaque can grow suddenly rather than gradually. It is one route by which a modest plaque becomes a dangerous one quickly.

Definition

Intravascular ultrasound, or IVUS, uses a tiny ultrasound probe threaded inside a coronary artery to photograph the wall from within.

Why it matters

It is the closest thing we have to seeing plaque directly in a living person. Studies using it are how we know that aggressive cholesterol lowering can genuinely shrink plaque, not just slow it down.

Definition

Ischemia is when a tissue is not getting enough blood and oxygen for what it is being asked to do.

Why it matters

In the heart it may cause chest pressure or breathlessness — or nothing at all. Silent ischemia is common in very fit people and in people with diabetes, which is exactly what makes it dangerous.

Definition

An ischemic stroke happens when blood flow to part of the brain is blocked and brain tissue starts to die.

Why it matters

Warning signs come on suddenly: a drooping face, a weak arm, slurred speech, sudden vision or balance trouble. Every minute counts, so this is a call-911-immediately situation, not a wait-and-see one.

Definition

A J-curve describes a pattern where risk is higher at both very high and very low values of something, with a sweet spot in the middle. Plotted on a graph it looks like the letter J.

Why it matters

It comes up most with blood pressure. Bringing very high pressure down clearly helps, but pushing it extremely low may not help everyone, especially older people with stiff arteries.

Definition

JUPITER tested a statin in people whose cholesterol was normal but whose CRP was elevated, suggesting hidden inflammation.

Why it matters

Events dropped substantially, and the trial is a landmark in the argument that inflammation carries risk independent of cholesterol. Critics note the statin lowered both, so the two effects are hard to separate.

Definition

A ketogenic diet is very low in carbohydrates and very high in fat, which pushes the body to burn fat and make ketones for fuel.

Why it matters

It often improves weight, blood sugar, and triglycerides. But cholesterol responses vary enormously — some people barely change while others see their LDL and ApoB shoot up dramatically. Better blood sugar does not cancel out a large rise in harmful particles.

Definition

Kidney disease means the kidneys have lost some of their ability to filter waste from your blood.

Why it matters

It raises heart risk on its own, separately from anything else. Damaged kidneys drive up blood pressure, promote inflammation, and disturb the way calcium is handled in blood vessels.

Definition

LDL, or low-density lipoprotein, is the main particle that carries cholesterol through your blood — and the main one that gets stuck in artery walls.

Why it matters

Be careful with the word. Sometimes LDL means the particles themselves, and sometimes it means the cholesterol inside them. Those are different things, and confusing them is behind a lot of misleading lab results.

Definition

LDL apheresis is a treatment that filters harmful cholesterol particles directly out of the blood, using a machine similar to dialysis. It is usually done every week or two.

Why it matters

It is reserved for people with severe inherited cholesterol conditions who cannot get low enough on medication alone. The effect is dramatic but temporary, since the liver keeps producing more.

Definition

LDL cholesterol, or LDL-C, is the amount of cholesterol sitting inside your LDL particles. It is the number on almost every standard lab report.

Why it matters

Here is the catch: it measures cargo, not vehicles. Two people with identical LDL-C can be carrying very different numbers of particles. The one with more particles has more risk, and the standard panel won't tell them.

Definition

LDL particle number counts how many LDL particles are circulating, rather than how much cholesterol they contain.

Why it matters

It catches people whose cholesterol looks acceptable but who are carrying a large number of relatively empty particles. ApoB does much the same job and is cheaper and more widely available.

Definition

The LDL receptor is a docking port on liver cells that grabs LDL particles out of the blood and pulls them in to be broken down.

Why it matters

The more of these ports you have working, the cleaner your blood stays. Statins, ezetimibe, PCSK9 inhibitors, and inclisiran all end up doing the same basic thing: increasing the number of working receptors.

Definition

LDLR is the gene that builds the LDL receptor, the docking port your liver uses to pull cholesterol particles out of circulation.

Why it matters

Faults in this gene are the most common cause of familial hypercholesterolemia. How much working receptor a person can build largely determines how high their cholesterol runs from birth.

Definition

A lean mass hyper-responder is someone lean and athletic whose LDL cholesterol rises enormously on a low-carbohydrate diet — sometimes to levels normally seen only in inherited disorders.

Why it matters

Supporters argue that in a metabolically healthy person this pattern may be harmless. That claim has not been tested against hard outcomes like heart attacks, so it remains an open question rather than a settled one.

Definition

Leucine is one of the building blocks of protein, and the one that acts as a switch telling muscle to start rebuilding itself.

Why it matters

Older muscle needs a bigger push on that switch than young muscle does. That is why protein advice for a 70-year-old athlete looks different from advice for a 25-year-old.

Definition

Lifestyle medicine uses everyday behavior — food, movement, sleep, stress, not smoking — to prevent and treat disease.

Why it matters

These changes are genuinely powerful and improve almost every measure of health. What they usually cannot do on their own is fully correct severe inherited cholesterol problems or erase decades of accumulated damage.

Definition

Linoleic acid is the main polyunsaturated fat in seed oils such as soybean, sunflower, and corn oil. Your body cannot make it, so you must get it from food.

Why it matters

Replacing saturated fat with it reliably lowers LDL cholesterol. Claims that it causes inflammation have circulated widely online but have held up poorly when actually tested in people.

Definition

The lipid core is the soft, greasy center of a plaque, made of cholesterol and the debris of dead immune cells.

Why it matters

A big core under a thin cap is the dangerous combination. Strong cholesterol treatment shrinks that core and thickens the cap, which is why plaques can become much safer even when they don't get much smaller.

Definition

Lipid lowering means reducing the harmful, ApoB-carrying particles in your blood — through food, medication, or both.

Why it matters

How much benefit you get depends on three things: how far the particles come down, how early you start, and how long you keep it up. Starting earlier is worth more than most people assume.

Definition

A lipoprotein is a tiny package that carries fat and cholesterol through your bloodstream. Since fat won't dissolve in water, it needs a protein wrapper to travel.

Why it matters

There are several kinds — chylomicrons, VLDL, IDL, LDL, HDL, and Lp(a). Which ones you have too many of matters more than your total cholesterol number.

Definition

Lipoprotein lipase is an enzyme anchored to the walls of small blood vessels that strips triglycerides out of passing particles and hands the fat to muscle and fat tissue.

Why it matters

When it works poorly, triglyceride-rich particles linger in the blood and turn into the remnants that lodge in artery walls. Several proteins your body makes, including ApoC-III and ANGPTL3, exist to throttle it.

Definition

Lipoprotein(a), written Lp(a) and said "L-P-little-a," is an LDL-like particle with an extra sticky protein attached.

Why it matters

Your level is set almost entirely by genetics — diet and exercise barely budge it. A high level raises the risk of heart attack, stroke, and narrowed aortic valves. Every adult should have it checked at least once, since one test answers the question for life.

Definition

Low-attenuation plaque is the very darkest, fattiest plaque on a CT scan — soft enough that X-rays pass through it easily.

Why it matters

Of everything a scan can measure, the amount of this material has turned out to be among the strongest predictors of a future heart attack, outperforming both calcium score and percentage narrowing.

Definition

LPA is the gene that determines how much lipoprotein(a) you make. Your version is fixed at conception.

Why it matters

This is why Lp(a) barely responds to diet or exercise, and why a single measurement is usually enough for life. Variation in this one gene explains most of the difference between people.

Definition

The lumen is the open channel inside a blood vessel where blood actually flows.

Why it matters

Older tests only showed the lumen. The trouble is that arteries bulge outward as plaque grows, so the lumen can look wide open while the wall is full of disease. A clear lumen is not a clean artery.

Definition

A macrophage is a large immune cell that swallows debris and invaders. The name literally means "big eater."

Why it matters

In an artery wall, macrophages eat trapped cholesterol particles, become bloated foam cells, and eventually die there. Their remains build the core of a plaque.

Definition

A major adverse cardiovascular event, or MACE, is a bundle of bad outcomes counted together in a study — typically cardiovascular death, heart attack, and stroke.

Why it matters

Watch this one closely when reading trials. Different studies bundle different things, and a headline improvement can sometimes be driven almost entirely by one minor component rather than by fewer deaths.

Definition

A masters athlete is a competitor over about 35 who trains and races seriously, often for decades.

Why it matters

This group challenges standard assumptions. They have exceptional fitness alongside sometimes surprising coronary calcium, altered protein needs, and a raised risk of atrial fibrillation — so ordinary advice can fit them badly.

Definition

Matrix metalloproteinases are enzymes that cut through the collagen scaffolding of tissue. Immune cells inside plaques release them.

Why it matters

They are the demolition crew that thins a fibrous cap from below. This is the mechanism by which inflammation converts a stable plaque into one that can rupture.

Definition

The Mediterranean diet emphasizes vegetables, fruit, beans, whole grains, nuts, and olive oil, with fish and little red meat.

Why it matters

It has strong evidence for reducing heart attacks and strokes. What it has not clearly shown is the ability to shrink existing coronary plaque — a different and higher bar that only a few very intensive diets have been tested against.

Definition

Mendelian randomization is a clever research method that uses the genes people were born with as a natural experiment.

Why it matters

Because genes are shuffled randomly at conception, comparing people who inherited naturally low cholesterol with those who didn't sidesteps the usual confusion about lifestyle. It is a major reason we are confident cholesterol particles cause heart disease rather than just accompanying it.

Definition

Menopause is when a woman's periods stop permanently, usually around age 51, as estrogen levels fall.

Why it matters

Cardiovascular risk tends to climb afterward. Cholesterol rises, blood pressure often increases, and fat redistributes toward the abdomen. It is a good moment to get a full risk assessment rather than assuming heart disease is a men's problem.

Definition

MESA, the Multi-Ethnic Study of Atherosclerosis, followed thousands of adults with no known heart disease, scanning their arteries and tracking outcomes.

Why it matters

It is the source of much of what we know about calcium scores in practice — including how a score of zero predicts low risk, and how quickly that reassurance fades with age.

Definition

A meta-analysis statistically combines the results of many separate studies into one overall estimate.

Why it matters

Pooling gives more precision than any single trial. But it inherits whatever flaws the original studies had — combining weak studies produces a confident-looking answer built on weak foundations.

Definition

Metabolic health describes how well your body handles blood sugar, blood pressure, fats, and body fat storage.

Why it matters

You can be thin and metabolically unhealthy, or heavier with good numbers. But good metabolic health does not cancel out a high ApoB or a high Lp(a) — those still need addressing on their own.

Definition

Metabolic syndrome is a cluster of five problems that tend to travel together: a large waist, high triglycerides, low HDL, high blood pressure, and high blood sugar. Having three or more counts.

Why it matters

It usually points to insulin resistance underneath. It is a useful warning flag, but each piece still needs to be measured and treated in its own right.

Definition

Microvascular dysfunction is disease in the smallest blood vessels of the heart, too small to see on any angiogram.

Why it matters

A person can have genuine chest pain and real oxygen shortage while being told their arteries are clean. It is more common in women and in people with diabetes, and it needs different testing to find.

Definition

Monounsaturated fat is the main fat in olive oil, avocados, and most nuts.

Why it matters

Swapping saturated fat for it lowers LDL cholesterol. The benefit comes from the swap, though — pouring extra olive oil on top of an otherwise unchanged diet is not the same experiment.

Definition

Some people report aching or weak muscles after starting a statin. Real statin muscle injury exists, but it is rare.

Why it matters

Carefully designed studies where neither patient nor doctor knew who got the real pill found that most reported symptoms appeared just as often on placebo. This is called the nocebo effect — expecting a side effect can produce it. It matters because it leads many people to quit a medicine that was protecting them.

Definition

See Heart Attack for the full entry.

Definition

Myocarditis is inflammation of the heart muscle, usually triggered by a viral infection.

Why it matters

Most cases recover fully, but exercising through it can be dangerous and it is one recognized cause of sudden death in young people. Standard advice is to rest until cleared.

Definition

The myocardium is the muscular wall of the heart — the part that actually squeezes to push blood around your body.

Why it matters

When it is starved of oxygen for too long, the damage is permanent. Muscle that dies is replaced by scar tissue, which does not contract.

Definition

The napkin-ring sign is a distinctive pattern on a CT scan: a dark, fatty plaque core surrounded by a bright rim, so the cross-section resembles a ring.

Why it matters

It is one of the few high-risk plaque features a radiologist can spot by eye, and it flags a plaque considerably more likely to cause trouble.

Definition

The necrotic core is the dead, mushy center of an advanced plaque, built from immune cells that ate trapped cholesterol and then died in place.

Why it matters

A large core makes a plaque fragile. It is one of the main features that turns a quiet plaque into one that might crack open and cause a heart attack.

Definition

Neovascularization is the growth of new blood vessels. Inside a plaque, they sprout from the vessels feeding the artery's own wall.

Why it matters

These new vessels are leaky and fragile. They deliver more inflammatory cells into the plaque and are the usual source of bleeding within it.

Definition

Neu5Gc is a sugar molecule found in red meat. Humans lost the ability to make it millions of years ago, but we still absorb it when we eat beef, pork, or lamb.

Why it matters

Because our bodies see it as foreign, we make antibodies against it. Some researchers think this low-grade immune reaction against our own tissues may be one reason red meat is tied to heart disease.

Definition

Niacin is vitamin B3, which at very high doses lowers LDL and raises HDL.

Why it matters

It looked promising for decades. Then large trials adding it to statins showed no benefit and more side effects, and it was largely abandoned — another casualty of the idea that raising HDL helps.

Definition

Nitric oxide is a gas your blood vessel lining makes to tell the vessel to relax and widen.

Why it matters

More nitric oxide means better blood flow and lower pressure. When the lining is damaged by smoking, high blood sugar, or high particle counts, it makes less of it — one of the very first steps toward heart disease.

Definition

NLRP3 is an alarm system inside immune cells. When it detects something it treats as a threat, it triggers a burst of inflammatory signaling.

Why it matters

Cholesterol crystals inside a plaque can set it off, which is one of the clearest mechanical links between trapped cholesterol and inflammation. It is the pathway colchicine is thought to dampen.

Definition

The nocebo effect is the placebo effect in reverse: if you expect a medicine to cause a side effect, you are more likely to actually feel it.

Why it matters

This is not imaginary — the discomfort is real. It matters enormously with statins, where studies giving people real pills and dummy pills without telling them found muscle aches happening at nearly the same rate in both groups.

Definition

Non-calcified plaque is the soft, fatty portion of a plaque that has not hardened with calcium. It shows up dark on a CT scan.

Why it matters

This is the part most likely to rupture. It is also invisible to a plain calcium scan, which is why a low calcium score in a young person is less reassuring than it sounds.

Definition

Non-HDL cholesterol is a simple calculation: your total cholesterol minus your HDL. What's left is the cholesterol riding in all the particles that can harm your arteries.

Why it matters

It costs nothing extra, appears on every lab report you already have, and predicts risk better than LDL alone. If you cannot get an ApoB test, this is the next best thing.

Definition

NPC1L1 is the transporter in your intestine that absorbs cholesterol from food and bile. Ezetimibe blocks it.

Why it matters

People born with a less active version absorb less cholesterol and have fewer heart attacks — genetic confirmation, arriving before the drug trials finished, that this was a worthwhile target.

Definition

Number needed to treat, or NNT, is how many people must take a treatment for one of them to benefit.

Why it matters

An NNT of 50 means fifty people take the drug so that one avoids a heart attack. It sounds discouraging until you realize nobody knows in advance who the one will be — and that most preventive medicine works this way.

Definition

Obesity means carrying enough excess body fat to affect health.

Why it matters

Where the fat sits matters as much as how much there is. Fat packed deep around the organs is far more harmful than the same weight carried on the hips and thighs, which is why two people at the same weight can have very different risk.

Definition

An observational study watches what people already do and tracks what happens to them. Nobody is assigned anything.

Why it matters

These studies are where most nutrition headlines come from. They are useful for generating ideas, but people who choose a habit differ in dozens of other ways, so they cannot prove the habit caused the result.

Definition

ODYSSEY OUTCOMES tested alirocumab in patients recovering from a recent heart attack.

Why it matters

It reduced repeat events and, in the highest-risk patients, deaths. Together with FOURIER it established PCSK9 inhibitors as genuine outcome drugs rather than just powerful number-movers.

Definition

Olive oil is the main fat of the Mediterranean diet, rich in monounsaturated fat and, in the extra virgin form, in plant compounds called polyphenols.

Why it matters

It is a reasonable fat to build a diet around. Where the evidence gets stretched is in claims that it is uniquely protective — much of its benefit appears to come from replacing worse fats rather than from special properties of its own.

Definition

Omega-3s are fats found mainly in oily fish, walnuts, and flaxseed.

Why it matters

They clearly lower triglycerides at high doses. Whether ordinary fish oil capsules prevent heart attacks is much less certain, and trial results have been mixed depending on the dose and the exact form used.

Definition

Optical coherence tomography, or OCT, threads a light-based probe into a coronary artery. It sees roughly ten times finer detail than ultrasound.

Why it matters

It is the only tool that can actually measure the thickness of a plaque's fibrous cap in a living person. That makes it the standard for asking whether a treatment made a plaque safer.

Definition

The ORION trials tested inclisiran, the twice-yearly injection that silences PCSK9 production inside liver cells.

Why it matters

They showed LDL staying roughly halved with only two doses a year. The finding matters as much for adherence as for chemistry — a treatment you cannot forget to take.

Definition

Oxidative stress is an imbalance between damaging reactive molecules and the body's ability to neutralize them.

Why it matters

It contributes to modifying LDL particles inside the artery wall, which is what makes them inflammatory. Supplementing antioxidants has nonetheless failed to prevent heart attacks, so the mechanism has not translated into a treatment.

Definition

Oxidized LDL is an LDL particle that has been chemically damaged after getting stuck in an artery wall.

Why it matters

This damage is what makes the immune system treat it as an invader. A normal LDL particle is largely ignored; a damaged one triggers the whole inflammatory cascade that builds a plaque.

Definition

A p-value estimates how likely you would be to see a result at least this striking if the treatment did nothing at all.

Why it matters

The conventional cutoff of 0.05 is a convention, not a law of nature. A small p-value says a result is unlikely to be chance; it says nothing about whether the effect is large enough to matter to a patient.

Definition

PACMAN-AMI gave a PCSK9 inhibitor to patients immediately after a heart attack and imaged their non-culprit arteries with three different catheter techniques.

Why it matters

Plaque shrank, caps thickened, and fat content fell — all within a year. It showed how quickly aggressive lowering starts changing plaque structure.

Definition

PCSK9 is a protein made by your liver that destroys the docking ports your liver uses to pull cholesterol out of your blood.

Why it matters

Fewer ports means more cholesterol staying in circulation. People born with a broken version of this protein have low cholesterol and remarkably few heart attacks — a discovery that led directly to a whole class of new drugs.

Definition

A PCSK9 inhibitor is a medicine that blocks that cholesterol-destroying protein, leaving more docking ports available to clear particles from the blood.

Why it matters

These are injections, not pills, given every two to four weeks. They can cut LDL and ApoB by half or more even on top of a statin, and they are especially valuable for inherited high cholesterol.

Definition

PDAY, short for Pathobiological Determinants of Atherosclerosis in Youth, examined the arteries of young people aged 15 to 34 who died of other causes.

Why it matters

Raised lesions were already present in a substantial fraction of them, and the amount tracked with their cholesterol and smoking. Along with Bogalusa, it is why prevention is now discussed as a lifelong project.

Definition

Percent atheroma volume, or PAV, is the share of an artery segment taken up by plaque rather than open channel.

Why it matters

It is the standard yardstick in plaque-regression trials. Because it is a percentage of the whole vessel, it is fairer than measuring one spot — and it reveals how small real regression is, usually a change of one or two percentage points.

Definition

Peripheral artery disease is plaque narrowing the arteries in your legs.

Why it matters

The classic symptom is cramping calf pain when walking that goes away with rest. It is important beyond the legs: if plaque is bad enough there to cause symptoms, it is almost certainly present in the heart too.

Definition

Phytosterols are the plant equivalents of cholesterol, found in nuts, seeds, and vegetable oils, and added to some margarines.

Why it matters

They block some cholesterol absorption and lower LDL by a few percent. A rare inherited condition causes them to build up dangerously, which is why they are not simply harmless in everyone.

Definition

A placebo is a dummy treatment — a sugar pill or a saline injection — given so researchers can tell what a real drug actually does.

Why it matters

People genuinely improve on placebos, which is exactly why it is needed. Without a placebo group, you cannot separate the drug's effect from hope, attention, and time.

Definition

A plant-based, or plant-predominant, diet is built mostly around vegetables, fruit, beans, whole grains, nuts, and seeds, with animal foods limited or absent.

Why it matters

These diets reliably lower LDL and ApoB, mostly by cutting saturated fat and adding fiber. Whether they do anything extra for arteries beyond that particle-lowering effect is an active and unsettled research question.

Definition

Plaque is the buildup of cholesterol, immune cells, scar tissue, and calcium inside an artery wall.

Why it matters

It is not like grease coating the inside of a pipe. It grows within the wall itself, often for thirty years or more, without causing a single symptom.

Definition

Plaque burden is the total amount of plaque in your arteries, everywhere — not just at the single worst spot.

Why it matters

This turns out to predict heart attacks better than how narrow any one artery is. Someone with widespread mild disease can be at higher risk than someone with one impressive-looking blockage.

Definition

Plaque erosion is when the lining over a plaque simply wears away and a clot forms, without the cap tearing open.

Why it matters

It causes a meaningful share of heart attacks, and it behaves differently from rupture — often in younger patients, more often in women and smokers. It may respond differently to treatment.

Definition

Plaque regression means existing plaque actually gets smaller, rather than just growing more slowly.

Why it matters

It is possible, and it has been photographed happening with intensive cholesterol lowering. But the changes are modest — usually a few percent of plaque volume. Beware anyone promising to melt your arteries clean.

Definition

Plaque rupture is when the protective cap over a plaque tears open, spilling its contents into the bloodstream.

Why it matters

Your body responds the way it responds to any wound: it forms a clot. Except this clot is inside a coronary artery, and it can block it completely within minutes. This is how most heart attacks actually happen.

Definition

Plaque stabilization is making an existing plaque less likely to crack open — thickening its cap, shrinking its greasy core, and calming the inflammation inside it.

Why it matters

This is probably the main reason cholesterol medicines start preventing heart attacks within months, long before any measurable amount of plaque has disappeared. Safer matters more than smaller.

Definition

Plaque volume is the total physical amount of plaque in a stretch of artery, measured in cubic millimeters.

Why it matters

It captures something percentage narrowing misses. An artery can hold a large volume of plaque while looking barely narrowed, because the vessel expanded outward to accommodate it.

Definition

A polygenic risk score adds up the effects of many small genetic variants to estimate your inherited risk of a disease.

Why it matters

No single one of these variants means much. Together they can identify people whose risk is as high as someone with a well-known inherited cholesterol disorder, even though no single gene stands out.

Definition

Polyunsaturated fat is found in seed oils, nuts, seeds, and fish. Omega-3 and omega-6 fats both belong to this family.

Why it matters

Replacing saturated fat with it lowers LDL cholesterol and, in good trials, reduces heart events. It is the swap that matters, not simply adding more.

Definition

Positron emission tomography, or PET, uses a mildly radioactive tracer to show which tissues are metabolically busy.

Why it matters

In arteries it can highlight active inflammation or calcification happening right now, rather than the accumulated damage a CT shows. It is mostly a research tool at present.

Definition

Postprandial lipemia is the surge of fat particles in your blood in the hours after eating a meal containing fat.

Why it matters

Most lipid panels are drawn fasting, so they miss this entirely. Yet arteries spend most of the day in the fed state, and an exaggerated post-meal surge may carry risk a fasting number never reveals.

Definition

Prediabetes means blood sugar is higher than normal but not yet high enough to be called diabetes.

Why it matters

It is often dismissed as borderline, which is a mistake. Artery damage and the shift toward small, numerous cholesterol particles are already underway at this stage.

Definition

PREDIMED randomly assigned thousands of high-risk Spanish adults to a Mediterranean diet with extra olive oil, the same diet with extra nuts, or a low-fat control diet.

Why it matters

It is the most influential dietary trial in cardiology and reported roughly 30 percent fewer major events. It was retracted and republished after randomization problems were found at some sites, with similar conclusions.

Definition

Preeclampsia is dangerously high blood pressure developing during pregnancy, often with protein in the urine.

Why it matters

It is now recognized as an early warning of lifelong cardiovascular risk. Women who had it face substantially higher rates of later heart disease and stroke, so a pregnancy history belongs in any risk assessment.

Definition

Primary prevention is treating someone who has never had a heart attack or stroke, to keep the first one from happening.

Why it matters

The bar for treatment is higher here than for someone who already has known disease, because the benefit per person is smaller. This distinction is why aspirin advice differs so sharply between the two groups.

Definition

Proprotein convertases are enzymes that activate other proteins by cutting them. PCSK9 belongs to this family — its full name is proprotein convertase subtilisin/kexin type 9.

Why it matters

The name explains the abbreviation. PCSK9 is the ninth member of the family to be identified, and the only one that turned out to be a major cholesterol target.

Definition

A prospective cohort enrolls healthy people, records their characteristics, and then waits to see what happens.

Why it matters

Measuring exposures before anyone gets sick avoids the problem of asking sick people to remember their old habits. It still cannot prove cause, because participants chose their own behavior.

Definition

Protein is the nutrient your body uses to build and repair muscle and tissue.

Why it matters

How much you need changes with age. Older adults, especially active ones, need noticeably more than the standard recommendation to maintain muscle — the amount that suffices at 30 leaves a 70-year-old slowly losing ground.

Definition

Proteoglycans are sticky sugar-and-protein molecules in the artery wall. ApoB particles bind to them and get held in place.

Why it matters

This is the trapping step. A particle that enters and leaves again causes no harm; one that sticks starts a plaque. It explains why the number of particles passing through matters so much.

Definition

Publication bias is the tendency for studies with striking positive results to get published while studies finding nothing quietly disappear.

Why it matters

It makes the published literature look more favorable than reality. It is a major reason why exciting early findings so often shrink when larger trials are run.

Definition

Pulse wave velocity measures how fast the pressure wave from each heartbeat travels along your arteries. Stiffer arteries carry it faster.

Why it matters

It is the standard measure of arterial stiffness and one of the better estimates of how old your blood vessels behave, independent of your birthday.

Definition

Quantitative coronary angiography is a way of measuring artery narrowing precisely from angiogram images, rather than eyeballing it.

Why it matters

Early studies of whether diet or drugs could reverse heart disease relied on this method. It measures the open channel only, which is why its findings need careful interpretation.

Definition

A randomized controlled trial assigns people to a treatment or a comparison group purely by chance, then follows both groups.

Why it matters

Randomizing is the whole trick. It means the two groups should be alike in every way except the treatment, so any difference in outcome can fairly be blamed on the treatment itself. It is the strongest evidence medicine has.

Definition

Reactive oxygen species are unstable oxygen-containing molecules produced as a by-product of normal metabolism.

Why it matters

In moderation they act as useful signals. In excess they damage proteins, fats, and DNA — including the LDL particles trapped in an artery wall.

Definition

Red meat includes beef, pork, and lamb.

Why it matters

It is linked to higher heart risk through several possible routes: saturated fat raising cholesterol particles, gut bacteria turning its nutrients into TMAO, and an immune reaction to a foreign sugar it contains. How much each route contributes is still debated.

Definition

Relative risk compares two groups: this group had 30 percent fewer heart attacks than that group.

Why it matters

It is the number used in almost every headline, and it can be deeply misleading on its own. Thirty percent off a large risk is meaningful. Thirty percent off a tiny risk is almost nothing. Always ask what it is 30 percent of.

Definition

Remnant cholesterol is the cholesterol carried in the leftovers of triglyceride-rich particles, after they have dropped off most of their fat.

Why it matters

These leftovers are small enough to get into artery walls and are thought to be particularly good at causing trouble. They are a major reason people with high triglycerides carry extra risk that LDL alone does not capture.

Definition

Residual risk is the risk that remains after you have done the obvious things — cholesterol treated, blood pressure controlled, not smoking.

Why it matters

It comes from sources like Lp(a), ongoing inflammation, insulin resistance, and kidney disease. Recognizing it is what pushes doctors to look past the standard checklist when someone keeps having events anyway.

Definition

Resistance training is working your muscles against a load — weights, bands, or your own body weight.

Why it matters

It was long treated as separate from heart health, something for building muscle rather than protecting arteries. That view has shifted. It improves blood pressure, blood sugar, and body composition, and it protects the muscle that aging otherwise takes away.

Definition

The response-to-retention hypothesis holds that atherosclerosis begins when ApoB particles are retained in the artery wall, with inflammation following as a consequence.

Why it matters

It is the organizing idea behind modern prevention. It settles the chicken-and-egg question by putting the particle first: no retained particles, no plaque, however much inflammation is present.

Definition

REVERSAL compared moderate and intensive statin therapy, using intravascular ultrasound to measure what happened to coronary plaque.

Why it matters

Plaque kept growing on the moderate dose and stopped on the intensive one. It was an early demonstration that how far you lower LDL changes the disease itself, not just the risk statistics.

Definition

Reverse causation is when the arrow points the other way — the illness caused the exposure rather than the exposure causing the illness.

Why it matters

It explains several persistent myths. Low cholesterol appears linked to cancer partly because early undiagnosed cancer lowers cholesterol, and non-drinkers look unhealthy partly because some quit drinking due to illness.

Definition

Reverse cholesterol transport is the process of moving cholesterol out of tissues, including artery walls, and back to the liver for disposal. HDL particles do the hauling.

Why it matters

How well this system works appears to matter more than how much HDL you have. That is likely why drugs that simply raised HDL numbers failed to prevent heart attacks.

Definition

Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the joints.

Why it matters

The inflammation is not confined to joints. People with it develop cardiovascular disease earlier and more often than their standard risk factors predict, so guidelines treat it as a risk enhancer.

Definition

A risk calculator estimates your chance of a heart attack or stroke over the next ten years, using your age, cholesterol, blood pressure, and a few other inputs.

Why it matters

They are useful starting points but systematically underestimate risk in younger people, because ten-year windows hide a lifetime of accumulating exposure. Most also ignore family history and Lp(a) entirely.

Definition

A risk factor is something that raises your chance of developing a disease — high cholesterol particles, high blood pressure, smoking, diabetes, family history.

Why it matters

Some you can change and some you cannot. The encouraging finding is that people who keep all the changeable ones in good shape from a young age develop remarkably little heart disease.

Definition

Rosuvastatin, sold as Crestor, is the most potent statin available and stays largely in the liver rather than spreading through the body.

Why it matters

It produces the largest LDL reductions of any statin and was the drug used in the trials that first demonstrated plaque regression.

Definition

SAMSON was an unusual trial in which patients who had quit statins because of side effects took, in random order, the statin, an identical placebo, and no pill at all.

Why it matters

Symptoms were nearly as bad on the placebo as on the real drug. It is the strongest evidence that most statin side effects are a nocebo response, and many participants restarted treatment afterward.

Definition

Sarcopenia is the progressive loss of muscle mass and strength that comes with age.

Why it matters

It predicts falls, disability, and death, and it accelerates sharply after about 60. Resistance training and adequate protein are the only well-established defenses, and both become more important with age rather than less.

Definition

Saturated fat is the kind that stays solid at room temperature — butter, the fat in red meat, coconut oil, and palm oil.

Why it matters

It raises LDL cholesterol by making your liver less efficient at clearing particles from your blood. Replacing it with unsaturated fat lowers cholesterol. Replacing it with sugar and refined flour does not, which is where a lot of confusing advice came from.

Definition

SATURN compared the two strongest statins head to head at maximum dose, measuring coronary plaque with intravascular ultrasound.

Why it matters

Both shrank plaque and the difference between them was small. What predicted regression was how low the LDL went, not which brand delivered it.

Definition

Secondary prevention is treating someone who has already had a heart attack, stroke, or stent, to stop the next one.

Why it matters

The math here is completely different from prevention in a healthy person. Risk is high, benefit per person is large, and treatments that are optional for a healthy 45-year-old become close to essential.

Definition

Seed oils are cooking oils pressed from seeds — soybean, sunflower, canola, corn, safflower.

Why it matters

They have become a popular villain online, blamed for inflammation and disease. When actually tested, replacing saturated fat with them lowers LDL cholesterol and, in controlled trials, reduces heart events. The claimed inflammatory harm has not held up well in humans.

Definition

Semaglutide is the medicine sold as Ozempic and Wegovy. It mimics a gut hormone that reduces appetite and improves blood sugar.

Why it matters

It produces large weight loss, but its heart benefits appear earlier than the weight loss can explain — which suggests it is acting on blood vessels and inflammation directly.

Definition

SGLT2 inhibitors are diabetes pills that make the kidneys flush excess sugar out in the urine.

Why it matters

Their biggest surprise was outside diabetes: they reduce hospitalization for heart failure and slow kidney disease, including in people without diabetes at all.

Definition

Silent ischemia is when the heart muscle is starved of oxygen but the person feels nothing at all.

Why it matters

Highly trained athletes are particularly prone to it. Years of hard exercise raise pain tolerance, build backup blood vessels, and teach people to ignore discomfort. The result is severe disease that produces no warning until something serious happens.

Definition

Sleep apnea is repeated pausing of breathing during sleep, usually because the airway collapses.

Why it matters

Each pause drops oxygen and jolts the nervous system. Over years this drives high blood pressure, atrial fibrillation, and insulin resistance. It is common, often undiagnosed, and treatable.

Definition

Small dense LDL particles are LDL particles that are smaller and carrying less cholesterol than usual.

Why it matters

They are more common in people with insulin resistance and high triglycerides. Because each one holds less cholesterol, you need many more of them to reach the same LDL number — so a normal result can be hiding a very high particle count.

Definition

Smoking damages the lining of your blood vessels, raises blood pressure, makes blood clot more easily, and speeds up plaque growth.

Why it matters

It is the single most damaging modifiable risk factor for the heart. The good news is that risk starts dropping within months of stopping and keeps falling for years.

Definition

Smooth muscle cells make up the middle layer of an artery and control how much the vessel tightens or relaxes.

Why it matters

During plaque formation they migrate inward and build the fibrous cap, which is protective. But they can also change character and take on cholesterol themselves, contributing to the plaque they are covering.

Definition

SPRINT tested whether pushing systolic blood pressure below 120 was better than the usual target of under 140.

Why it matters

The tighter target reduced events and deaths, and changed guidelines worldwide. It also increased some side effects, so the right target still depends on the individual.

Definition

SR-B1 is the receptor on liver cells that takes cholesterol from HDL particles and releases it for disposal in bile.

Why it matters

It completes the return journey. Oddly, people with a broken version have high HDL but higher heart risk — another reason the HDL number alone tells you little.

Definition

A statin slows the enzyme your liver uses to make cholesterol. Your liver responds by pulling more cholesterol out of your blood, which is where the real benefit comes from.

Why it matters

Statins are the most studied cardiovascular medicines in existence, tested in hundreds of thousands of people. They lower LDL and ApoB, stabilize plaques, and reduce heart attacks and deaths.

Definition

Statistical power is a study's ability to detect a real effect if one exists. It depends mostly on how many events occur.

Why it matters

An underpowered trial that finds nothing has not shown the treatment does not work — only that the study was too small to tell. The two conclusions are constantly confused.

Definition

Stenosis is narrowing — usually described as a percentage, like a 70 percent blockage.

Why it matters

It gets more attention than it deserves. Most heart attacks come from plaques that were nowhere near 70 percent narrowed. What the plaque is made of matters more than how tight the squeeze is.

Definition

A stent is a small metal mesh tube expanded inside a narrowed artery to hold it open.

Why it matters

During a heart attack, stents save lives. For stable chest pain, large trials found they relieve symptoms but do not prevent future heart attacks better than medication alone. A stent fixes one spot; the disease lives in all your arteries.

Definition

A sterol is a family of waxy molecules built on the same four-ring structure. Cholesterol is the one animals make; plants make their own versions.

Why it matters

Plant sterols compete with cholesterol for absorption in the gut, which is why sterol-fortified spreads modestly lower LDL.

Definition

A stress test watches your heart while you exercise on a treadmill or bike, sometimes with imaging added.

Why it matters

It is designed to find arteries narrowed enough to limit blood flow under load. It misses a great deal of plaque, because a plaque can be large and dangerous without narrowing the artery enough to fail this test.

Definition

A stroke happens when blood flow to part of the brain stops, either from a blockage or from bleeding.

Why it matters

Signs come on suddenly: face drooping, arm weakness, slurred speech, sudden vision or balance problems. Call emergency services immediately — treatments that limit the damage only work within a short window.

Definition

Subclinical atherosclerosis means plaque is present but has not yet caused any symptoms or events.

Why it matters

This describes an enormous number of apparently healthy adults. It is the whole reason imaging tests exist: to find the disease during the decades when it is silent and still highly treatable.

Definition

The subendothelial space is the narrow gap just beneath the artery's inner lining, between that single layer of cells and the muscle beneath.

Why it matters

This is exactly where ApoB particles get trapped and where every plaque begins. Everything else in atherosclerosis follows from what accumulates in this thin layer.

Definition

Sudden cardiac death is when the heart abruptly stops and the person dies within minutes, often with no prior warning.

Why it matters

In older adults it usually follows a heart attack. In young athletes the causes are different — inherited heart muscle or electrical conditions. Fast CPR and a defibrillator are what change the outcome.

Definition

A surrogate marker is a stand-in measurement used because the thing you really care about takes too long to observe.

Why it matters

Cholesterol is a good surrogate — lowering it genuinely reduces heart attacks. Others have failed badly: drugs that improved the number on the report while patients did no better, or worse. A moved number is a promise, not a result.

Definition

A systematic review searches for every study on a question using a pre-declared method, then assesses them by consistent criteria.

Why it matters

The pre-declared search is the point. It prevents an author from quietly including studies that support their view and omitting those that do not.

Definition

Systolic blood pressure is the top number — the pressure in your arteries while your heart is squeezing.

Why it matters

In adults over about 50 it is the more important of the two numbers, because arteries stiffen with age and that stiffness pushes the top number up.

Definition

Testosterone is the main male sex hormone, though women produce it too in smaller amounts.

Why it matters

For heart purposes, the total number on a lab report can be misleading. Much of it is locked to a carrier protein and unavailable to your tissues, so two men with the same total can be in very different situations.

Definition

Thrombosis is a blood clot forming inside a blood vessel.

Why it matters

Clotting is a survival mechanism when you are bleeding. Inside a coronary artery, on top of a cracked plaque, it is what turns a slow disease into a sudden emergency.

Definition

Tirzepatide, sold as Mounjaro and Zepbound, acts on two gut hormone receptors rather than one.

Why it matters

It produces greater weight loss and blood sugar improvement than the single-target drugs, with cardiovascular outcome evidence still accumulating.

Definition

TMAO is a compound your gut bacteria produce from nutrients found in red meat, eggs, and some fish. Higher blood levels have been linked to heart disease.

Why it matters

Whether TMAO actually causes the damage or is simply a signal of a diet and gut pattern that does remains genuinely unsettled. Fish raises it more than steak does, which complicates the simple story considerably.

Definition

Total cholesterol adds together the cholesterol in all your particles, harmful and helpful alike.

Why it matters

Because it lumps everything into one number, it can hide more than it reveals. A person with high HDL and a person with high LDL can post the same total while facing very different risks.

Definition

Trans fat is an artificially altered fat once used to make processed foods last longer on the shelf.

Why it matters

It is the worst fat ever studied for the heart — it raises LDL and lowers HDL at the same time. It has now been banned or phased out in most countries, one of the clearest public health wins in nutrition.

Definition

Transcytosis is the process by which a cell picks something up on one side, carries it across, and releases it on the other.

Why it matters

This is how LDL particles cross the artery's inner lining. They do not slip through gaps — they are actively ferried across, which is why a perfectly intact lining still lets cholesterol in.

Definition

Triglycerides are the main form of fat in your blood and in your body's storage.

Why it matters

High levels usually signal that something metabolic is off — too much alcohol, insulin resistance, or excess calories. They also come packaged in particles whose leftovers can lodge in artery walls, so they carry risk of their own.

Definition

Troponin is a protein that leaks into the blood when heart muscle is damaged. A blood test for it is how heart attacks are confirmed.

Why it matters

Modern tests are so sensitive they can detect very small amounts, which sometimes turns up minor heart strain after extreme endurance events in otherwise healthy athletes.

Definition

UK Biobank holds detailed genetic, lifestyle, and health data on half a million British volunteers, linked to their medical records.

Why it matters

Its size and genetic depth make it the workhorse behind much modern Mendelian randomization — the method that separates causes from coincidences.

Definition

Unsaturated fat is liquid at room temperature and comes from plants and fish — olive oil, nuts, seeds, avocado, seed oils.

Why it matters

Replacing saturated fat with it lowers LDL cholesterol and reduces heart events. This is one of the most consistent findings in all of nutrition science.

Definition

Unstable angina is chest discomfort that appears at rest, comes on with less effort than before, or is suddenly getting worse.

Why it matters

Unlike stable angina, which is predictable, this pattern suggests a plaque has become active and a heart attack may be close behind. It is treated as an emergency.

Definition

The vasa vasorum are tiny blood vessels that supply the wall of a larger artery. The name means "vessels of the vessels."

Why it matters

An artery wall is thick enough to need its own blood supply. As a plaque grows, these vessels multiply into it — bringing inflammatory cells and the risk of bleeding inside the plaque.

Definition

Vascular age is an estimate of how old your arteries behave, compared with your actual age.

Why it matters

A 50-year-old can have arteries acting like a 65-year-old's, or a 40-year-old's. Unlike your birthday, this number can move in both directions depending on what you do about it.

Definition

VCAM-1 is a sticky molecule that appears on an inflamed vessel lining and grabs passing white blood cells so they can burrow into the wall.

Why it matters

It is one of the earliest steps in plaque formation, switching on before there is anything to see on a scan.

Definition

A vegetarian diet excludes meat, and a vegan diet excludes all animal products.

Why it matters

These diets are associated with longer life and less heart disease, but the comparison groups matter. Vegetarians also tend to smoke less, drink less, and exercise more, so untangling the diet from the lifestyle around it is genuinely difficult.

Definition

See Belly Fat for the full entry.

Definition

VLDL, or very-low-density lipoprotein, is the particle your liver makes to ship triglycerides out to the rest of the body.

Why it matters

As it drops off its cargo it shrinks, becoming IDL and then LDL. It carries ApoB the whole way, so it counts toward your harmful particle total from start to finish.

Definition

VO2 max is the maximum amount of oxygen your body can use during all-out exercise. It is the standard measure of cardiorespiratory fitness.

Why it matters

It is one of the strongest predictors of lifespan we have. It is also not a plaque test — world-class VO2 max values have been recorded in people with severe coronary disease.

Definition

A vulnerable plaque is one at high risk of cracking open: a thin cap, a large greasy core, active inflammation, and often outward bulging of the artery.

Why it matters

These plaques frequently do not narrow the artery much, which is exactly the problem. They can look unimpressive on a test right up until the day they cause a heart attack.

Definition

Waist circumference is simply the measurement around your middle, taken at the level of your belly button.

Why it matters

It is a rough but useful estimate of visceral fat, and it often tells you more about heart risk than the number on your scale. A tape measure is a genuinely underrated health tool.

Definition

Weight loss means reducing body fat, whether through food changes, exercise, medication, or surgery.

Why it matters

Losing visceral fat improves blood pressure, blood sugar, and triglycerides substantially. Its effect on ApoB is usually more modest, which is why weight loss alone often does not fix a high particle count.

Definition

A whole food plant-based diet is built from vegetables, fruit, beans, whole grains, nuts, and seeds, with animal products and processed foods largely removed.

Why it matters

The strictest versions are the only dietary approach that has been paired with imaging evidence of coronary plaque actually shrinking. Those studies were small and intensive, and the diets are demanding to sustain.

Definition

A xanthoma is a yellowish deposit of cholesterol that builds up in the skin or in tendons, most often around the knuckles, elbows, knees, or the Achilles tendon.

Why it matters

They are a visible sign of very high cholesterol, usually from an inherited condition. When they appear in a child, it points toward the severe inherited form and calls for urgent evaluation.

Definition

A zero calcium score means a CT scan found no hardened plaque in your heart's arteries at all.

Why it matters

For most middle-aged adults this is genuinely good news and predicts a low risk over the next decade. It is not a permanent clearance, though. Young people and those with very high Lp(a) can carry soft plaque that a calcium scan cannot see.