Atherosclerosis is a progressive, inflammatory cardiovascular disease characterized by the accumulation of lipids, inflammatory cells, smooth muscle cells, and fibrous tissue within the intima (innermost layer) of medium and large arteries. This buildup forms plaques (atheromas) that can calcify over time, reduce arterial elasticity, narrow the vessel lumen, and ultimately lead to ischemia, thrombosis, or complete vessel occlusion. It is a leading underlying cause of coronary artery disease, peripheral artery disease, stroke, and other cardiovascular events.
Atherosclerosis is the gradual buildup of plaque in the walls of your arteries. Arteries are blood vessels that carry oxygen-rich blood to organs and tissues throughout your body. Plaque (atheroma) is a sticky substance made of fat, cholesterol, calcium and other substances.
As plaque builds up, your artery wall grows thicker and harder. This “hardening of the arteries” is usually a silent process in the early stages. You may not notice symptoms for a long time. But eventually, as the plaque grows, the opening (lumen) of your artery narrows, leaving less room for blood to flow. This means less blood can reach your organs and tissues. Plus, the constant force of blood flow can lead to plaque erosion or rupture, causing a blood clot to form.
A narrowed artery is like a highway reduced to one lane. But a blood clot is like a barricade in the middle of the road. It blocks blood flow to certain organs or tissues the artery normally feeds. The effects on your body depend on where the blood clot forms. For example, blockages in a coronary artery deprive your heart of oxygen-rich blood, leading to a heart attack.
How common is atherosclerosis?
Atherosclerosis is very common. The complications of plaque buildup (including heart attacks and strokes) are the leading cause of death worldwide.
In America, about half of people age 45 to 84 have atherosclerosis but aren’t aware of it, according to the U.S. National Institutes of Health.
Symptoms and Causes
Back to video
Learn more about the signs of atherosclerosis.
What are the symptoms?
Atherosclerosis symptoms often don’t start until an artery is very narrow or blocked. Many people don’t know they have plaque buildup until they have a medical emergency like a heart attack or stroke.
You may notice symptoms of atherosclerosis if your artery is more than 70% blocked. You can have symptoms in different parts of your body, depending on the location of the blockage. Affected locations may include:
Heart
Coronary artery disease (CAD, which can lead to a heart attack) happens in the arteries that supply blood to your heart.
You may experience:
Shortness of breath (dyspnea) during light physical activity.
These factors can damage your artery’s inner lining (endothelium). This causes atherosclerosis to begin. The damage usually occurs slowly and over time.
Atherosclerosis codes are primarily found in categories I25 (Chronic ischemic heart disease) and I70 (Atherosclerosis). This is a large family — below are the most clinically essential codes.
⚠️ Coding Note: For inpatient coding, atherosclerosis of the coronary arteries should be coded with the highest level of specificity — always capture whether it involves native vessels vs. bypass grafts, the presence/type of angina, and complicating factors like lipid-rich plaque (I25.83) or calcified lesion (I25.84). The I70 category for peripheral atherosclerosis requires laterality, vessel type, and presence of ulceration/gangrene for full specificity.
Crystal's MCW Coder Hub