Coronary artery disease is an impairment of blood flow in your coronary arteries (the arteries that supply blood to the heart muscle itself). Most coronary artery disease (CAD) is caused by atherosclerosis, a disorder that causes thickening and hardening of the arteries. These changes in the blood vessels, like most causes of CAD, lead to narrowing/obstruction of the vessels, which results in a diminished blood supply to the heart muscle.
Other causes of CAD include:
- coronary spasm
- coronary artery embolism
Fatty material, cholesterol, and other substances can form a sticky material inside your arteries. This material is called plaque. When plaque builds up on the walls of your blood vessels, it’s called atherosclerosis.
When plaque builds up in your coronary arteries, it causes them to harden and narrow. When arteries are narrow, less blood is able to pass through them. Your blood delivers oxygen and other nutrients to your heart. If you have atherosclerosis, this means that your heart is not getting as much blood as it should. The heart is always working and needs a consistent minimum supply of oxygen and nutrients. When your heart doesn’t receive enough oxygen due to insufficient blood flow through the narrowed, atherosclerotic coronary arteries, this damages the heart muscle and it will eventually die if a regular, adequate supply is not restored.
Researchers believe that the buildup of plaque in the arteries begins with damage to the inner layers of the arteries. This damage may be caused by:
- high blood pressure
- high cholesterol and fat in the blood
- high blood sugar from diabetes or insulin resistance
- blood vessel inflammation
- radiation therapy to the chest (such as for certain cancers)
Over time, the plaque sticks to the injured areas and begins to accumulate. This buildup can inflame the arterial lining, which can cause scarring that thickens the arterial wall, reducing blood flow even further. These plaques in the arteries can also rupture, which can lead to clot formation and eventually cause a heart attack if the clot blocks the passage of blood to the heart.
A coronary artery spasm occurs when the muscles in the arterial wall tighten temporarily, narrowing the passage of blood. Spasms can occur in any arteries, not just in those with atherosclerosis. The sudden narrowing of the artery reduces blood flow to the heart and may cause angina (chest pain and pressure) or a heart attack.
No one knows exactly what causes coronary artery spasm, but it’s most common in people who smoke or have high blood pressure or high cholesterol. Spasms may occur spontaneously, but some events can trigger the spasm, such as:
- emotional stress
- exposure to cold
- stimulants such as cocaine and amphetamines
- alcohol withdrawal
- medications that narrow blood vessels (vasoconstrictors)
An embolism is an obstruction in a blood vessel that gets stuck while traveling through the bloodstream. The obstruction is usually a blood clot but it can also be air, fat, tumor tissue, or other foreign matter. An obstruction in a coronary artery can reduce or block blood flow to the heart muscle, which can lead to a heart attack.
The walls of the coronary arteries are composed of three layers. A dissection occurs when one or more of these layers separate. This separation allows blood to accumulate between the layers. The accumulation of blood between the layers of the arterial wall causes narrowing of the arterial space where blood normally flows and thus restricts blood flow to the heart.
Coronary dissection can also occur as a complication of a relatively common medical procedure known as cardiac catheterization. In this procedure, a small, flexible instrument is inserted into the coronary vessels in order to either identify or remove a preexisting obstruction to blood flow. Spontaneous coronary dissection, a rare cause of CAD, occurs most commonly in women with a condition known as fibromuscular dysplasia.
A coronary artery aneurysm is a bulge in a section of a coronary artery. It is more common in men than in women and occurs most often in the right coronary artery. Aneurysms are often caused by atherosclerosis because the blood can’t flow as it normally should and instead pools in a section of the artery. The walls become thinner because the bulge created by the aneurysm stretches the walls of the artery. When this is combined with a sluggish and irregular blood flow common in atherosclerosis, the artery can rupture and/or an embolus (clot) can form.
Vasculitis is an inflammation of the blood vessels. In many cases, the precise cause is unknown. It develops when your immune system attacks your blood vessels as though they were foreign invaders. Inflammation in the blood vessels can cause:
- narrowing of the vessels
- blockage of the vessels
- rupture of the vessels
Vasculitis is typically a systemic disease. That means it may affect blood vessels throughout your body. This may include your coronary arteries. Inflammation in your coronary arteries reduces blood flow to your heart muscle.