Atherosclerosis is a condition where fatty deposits called plaques build up inside your artery walls, gradually narrowing and stiffening the vessels that carry blood throughout your body. It’s the underlying cause of most heart attacks and strokes, and ischemic heart disease alone, its most common consequence, killed roughly 9.14 million people worldwide in 2019.
How Plaque Forms Inside Your Arteries
Your arteries are lined with a thin layer of cells called the endothelium. This lining does more than just sit there. It controls how much your blood vessels expand or contract, prevents blood from clotting where it shouldn’t, and acts as a gatekeeper deciding what passes into the artery wall. When that lining gets damaged, the entire process of atherosclerosis begins.
Damage to the endothelium can come from high blood pressure, smoking, high blood sugar, or even turbulent blood flow at places where arteries branch or curve. Once damaged, the lining becomes leaky, and LDL cholesterol (the “bad” cholesterol) starts seeping into the artery wall beneath it. There, the cholesterol particles get chemically modified through oxidation, which triggers an alarm signal.
Your immune system responds by sending white blood cells called monocytes to the site. These cells burrow into the artery wall and transform into macrophages, essentially cleanup cells designed to swallow the modified cholesterol. But they take in too much. Gorged with fat, these macrophages become what researchers call “foam cells” because of their bubbly appearance under a microscope. Clusters of foam cells form what’s known as a fatty streak, the earliest visible sign of atherosclerosis. Fatty streaks have been found in the arteries of people as young as their teens and twenties.
Over years and decades, these fatty streaks grow. Smooth muscle cells from deeper in the artery wall migrate toward the surface and produce a fibrous cap of tough tissue over the fatty core. The result is a mature plaque: a mound of fat, dead cells, calcium deposits, and fibrous tissue bulging into the artery and restricting blood flow.
Stable Plaques vs. Dangerous Ones
Not all plaques are equally dangerous, and the size of a plaque doesn’t always predict the risk. What matters most is its structure. A stable plaque typically has a thick, strong fibrous cap covering a relatively small core of fatty material. It may narrow the artery significantly but is less likely to cause a sudden heart attack or stroke.
A vulnerable plaque is a different story. Based on autopsy studies, a vulnerable plaque has three defining features: a thin fibrous cap (less than 65 micrometers thick), a large pool of lipids underneath, and a concentration of activated immune cells near the cap. When that thin cap ruptures, the fatty, necrotic core spills into the bloodstream, instantly triggering a blood clot. That clot can partially or completely block the artery within minutes, cutting off blood supply to whatever organ the artery feeds. This is the mechanism behind most heart attacks and many strokes.
Where Atherosclerosis Strikes
Atherosclerosis can develop in virtually any artery, but it gets different names depending on which vessels are involved:
- Coronary artery disease (CAD): plaque in the arteries feeding the heart muscle, the most common and most deadly form
- Carotid artery disease: plaque in the neck arteries supplying the brain, a major cause of stroke
- Peripheral artery disease (PAD): plaque in the arteries of the legs, arms, or pelvis, often causing pain during walking
- Renal artery stenosis: plaque in the arteries supplying the kidneys, which can contribute to high blood pressure and kidney damage
- Mesenteric artery ischemia: plaque in the arteries feeding the intestines, causing abdominal pain after eating
Many people have atherosclerosis developing in more than one of these areas at the same time, since the risk factors affect arteries throughout the body.
Why You Won’t Feel It Until It’s Advanced
One of the most important things to understand about atherosclerosis is that it produces no symptoms for most of its life. Plaques can grow for decades without causing any noticeable problems. Arteries have some ability to remodel and expand outward to accommodate growing plaques, so blood flow may remain adequate even as the disease progresses.
Symptoms typically appear only when an artery is narrowed enough to limit blood flow during exertion, or when a plaque ruptures and triggers a clot. In the heart, this might show up as chest pain or pressure during exercise. In the legs, it might mean cramping or heaviness when walking. In the arteries feeding the brain, it could cause brief episodes of weakness, vision changes, or slurred speech. For some people, the first sign of atherosclerosis is a heart attack or stroke with no prior warning at all. This is why screening and risk factor management matter so much, even when you feel perfectly healthy.
Major Risk Factors
High blood pressure is one of the strongest accelerators. It damages artery walls through sheer mechanical force, thickening them and making plaques more prone to rupture. Research has shown that even mild increases in blood pressure directly stimulate the progression of plaques, independent of other mechanisms.
High LDL cholesterol provides the raw material for plaque formation. The more LDL circulating in your blood, the more that infiltrates damaged artery walls. Current guidelines from the American Heart Association and American College of Cardiology recommend an LDL level below 100 mg/dL for people at moderate risk, below 70 mg/dL for those at high risk, and below 55 mg/dL for people who already have established cardiovascular disease.
Smoking is particularly destructive. Smokers under 60 have five times the risk of atherosclerosis compared to nonsmokers. For those over 60, the risk is doubled. Smoking damages the endothelial lining, promotes inflammation, and makes blood more prone to clotting.
Diabetes accelerates atherosclerosis through multiple pathways, including chronic inflammation and damage from elevated blood sugar. Other contributors include obesity, physical inactivity, a diet high in saturated fat and processed foods, chronic stress, and a family history of early heart disease.
How Atherosclerosis Is Detected
Because atherosclerosis is silent for so long, doctors often screen for it based on risk factors rather than waiting for symptoms. A physical exam can sometimes reveal clues like weak pulses, abnormal sounds in the arteries (called bruits), or differences in blood pressure between limbs.
CT angiography is one of the most informative imaging tools available. It can visualize the coronary arteries in detail, measure how much the lumen is narrowed, and characterize plaque composition, sorting plaques into calcified, partially calcified, or non-calcified types. It detects non-calcified plaques with roughly 90% accuracy when those plaques are thicker than 1 millimeter.
A coronary calcium score, measured with a quick CT scan, quantifies the amount of calcium in your heart’s arteries. Since calcification is part of the atherosclerotic process, a higher score indicates more extensive disease. Ultrasound of the carotid arteries can measure the thickness of the artery wall in real time, providing another window into early disease. For patients already known to have significant blockages, intravascular ultrasound, a tiny probe threaded inside the artery, gives the most detailed view of plaque size and structure.
Slowing and Reversing Plaque Buildup
Atherosclerosis was once considered a one-way street, a disease that could only get worse. That’s no longer true. Multiple clinical studies have shown that aggressive cholesterol-lowering therapy can stabilize plaques and, in some cases, shrink them. The key mechanisms behind plaque regression aren’t simply a reversal of how plaques form. Instead, the process involves removing lipids and dead cell material from the artery wall, thickening the fibrous cap to make it less likely to rupture, and halting the inflammatory cycle that drives plaque growth.
Cholesterol-lowering medications remain the cornerstone of treatment. In clinical trials, combining a statin with a cholesterol absorption blocker produced a more pronounced increase in fibrous cap thickness (0.08 mm vs. 0.04 mm with a statin alone) and a significant reduction in the size of lipid-rich plaques. The PACMAN-AMI trial went further, using three different imaging techniques simultaneously to confirm that adding a PCSK9 inhibitor (a newer class of cholesterol-lowering medication) to high-intensity statin therapy produced meaningful plaque regression and improved plaque stability even beyond what statins achieved on their own.
Lifestyle changes form the other half of the equation, and their effects are real, not just motivational advice. Regular aerobic exercise improves endothelial function, lowers blood pressure, raises HDL cholesterol, and reduces inflammation. A diet emphasizing vegetables, fruits, whole grains, fish, and unsaturated fats while limiting processed meats and refined carbohydrates directly lowers the amount of LDL available to infiltrate artery walls. Quitting smoking allows damaged endothelium to begin repairing itself, and the excess cardiovascular risk from smoking drops substantially within the first few years after stopping. Maintaining a healthy weight reduces the metabolic stress that drives chronic inflammation throughout the vascular system.
The earlier these interventions begin, the more effective they are. A 40-year-old who gets their LDL and blood pressure under control has decades of reduced plaque progression ahead of them, while someone who waits until their 60s is working against a much larger burden of established disease.