The heart receives its blood supply from the three coronary arteries that leave the aorta just outside the left ventricle. Like a tree, these three major arteries divide into smaller and smaller blood vessels until the entire heart wall is penetrated by hundreds of tiny blood vessels.
Coronary artery disease is caused by various gradual changes that occur in the coronary arteries. Collectively these changes are referred to as arteriosclero- sis, which means hardening and thickening (literally “scarring”) of the wall. Ath- erosclerosis is the most common type of arteriosclerosis. Atherosclerosis is the gradual thickening and hardening of an artery’s inner wall by the formation of fatty deposits called plaques. These plaques cause narrowing of the artery’s internal channel, thereby reducing the ﬂow of blood (and oxygen) to the heart. This is similar to the way layers of minerals form a deposit inside a water pipe; as the minerals accumulate, the stream of water becomes steadily smaller.
Atherosclerosis is the buildup of a cholesterol-containing substance called plaque inside arteries.Plaque often has a fatty core with a hard coating.The buildup of plaque can reduce or block the ﬂow of blood to vital organs.
Plaque and Blood Clots
A buildup of plaque inside an artery is often the start of a blood clot. Plaque tends to crack (top).Your body interprets these cracks as injuries and forms blood clots around them to seal them and allow them to heal (center).If a clot inside a coronary artery grows large enough (bottom), it can block blood ﬂow in the artery and cause a heart attack.
As the plaques become thicker, their surface becomes rougher. This encour- ages formation of blood clots within the artery. Small pieces of a blood clot can break off and travel through the bloodstream and block smaller blood vessels, causing a heart attack or stroke.
Atherosclerosis occurs more commonly in the coronary arteries than in other arteries of the body. The thickening of the artery wall progresses slowly until only a trickle of blood moves through the narrowed channel. The process may continue at the same rate until a small artery has been closed completely. As the artery gradually closes, the blood supply to the heart muscle becomes inade- quate, causing heart damage.
Coronary artery disease is the most common result of an inadequate blood supply to the heart muscle. The most common symptom of coronary artery dis- ease is angina (see below); the most serious consequence is a heart attack.