How does high cholesterol cause heart disease?

The term “cardiovascular disease” refers to medical conditions involving the heart and blood vessels. The most common type of cardiovascular disease is coronary artery disease (CAD). CAD occurs when arterial plaque builds up in the coronary arteries, blood vessels that carry blood to the heart. The medical term for the buildup of arterial plaque is atherosclerosis.

Plaque buildup can cause arteries to become narrow and stiff. This can reduce blood flow. When this occurs in the coronary arteries, the heart muscle receives less blood and less oxygen. This can weaken the heart muscle.

Complications can include arrhythmias (irregular heart rhythms) and heart failure (where the heart cannot pump enough blood). Blood vessels can also become completely blocked, causing heart attack or stroke.

Excess LDL is the main building block of arterial plaques

Cholesterol is carried through the body by particles called lipoproteins. There are two main types of lipoproteins that work together. Low-density lipoprotein (LDL) transports cholesterol to different organs and tissues, where it is used to make cell membranes, hormones, and other substances the body needs.

High-density lipoprotein (HDL) helps carry excess cholesterol from tissues and blood vessel walls to the liver, where it can be removed from the blood. Healthy HDL levels are associated with a lower risk of cardiovascular disease.

Arterial plaque forms as a result of several factors. One is damage to the endothelium, a layer of tissue that covers the inner walls of blood vessels. The other is excess amounts of LDL in the blood.

A simplified look at how arterial plaques form:

• Excess LDL in the blood becomes trapped in damaged sections of endothelium.
• The trapped LDL undergoes a chemical change called oxidation.
• Immune cells called scavenger cells move into the endothelium and consume the oxidized LDL.
• As scavenger cells fill with LDL, they become foam cells.
• Foam cells release chemicals that signal inflammation and cell growth.
• Inflammation causes additional damage to the endothelium. More LDL and debris accumulate. This accumulation creates the soft inner core of the plaque.
• A layer of smooth muscle (called a fibrous cap) forms to cover the plaque. This holds the plaque in place and prevents it from rupturing. It also causes the blood vessel to become narrow and stiff.

If a plaque ruptures, a blood clot can form and block a blood vessel completely. If a blood clot blocks a blood vessel that supplies the heart, it can cause a heart attack. A blockage in a blood vessel that supplies the brain can cause a stroke.

Other risk factors, including blood sugar

High cholesterol levels are not the only factors that contribute to arterial plaque. Other important risk factors include:

• Uncontrolled blood glucose. Chronically elevated blood glucose levels can cause damage to the endothelium inside blood vessels and promote the formation of arterial plaque. Many people with diabetes also have cardiovascular disease.
• Hypertension, or high blood pressure. Blood pressure is the force that blood exerts against the walls of blood vessels as it moves through the body. When blood pressure is too high for too long, it can cause damage to blood vessel walls, creating locations where LDL can collect and plaques can form.
• Chemicals in tobacco smoke damage blood vessel walls, lower HDL levels, and cause other problems that increase the risk of atherosclerosis and other heart problems.
• Overweight and obesity are linked with higher blood pressure, unhealthy cholesterol, uncontrolled blood glucose levels, and other risk factors for cardiovascular disease.

When several risk factors are combined, the risk of atherosclerosis and other heart problems will increase.

Working with a healthcare provider

A healthcare provider will be your best source of information. Talk to a healthcare provider about your risk of cardiovascular disease and what you can do to lower your risk.

Following a heart-healthy diet and getting regular exercise can improve cholesterol levels, blood glucose levels, and blood pressure. Many people also need to take medications to manage these numbers and prevent complications.

For anyone who smokes, quitting will lower the risk of cardiovascular disease and other health conditions, including chronic obstructive pulmonary disease (COPD) and many types of cancer. For a person with overweight/obesity, losing 5 to 10 percent of total body weight can often reduce risk and improve health.