Heart disease can be caused by a congenital problem with the heart, by infections such as rheumatic fever that damage the heart valves, or most commonly by atherosclerosis.

Atherosclerosis or hardening of the arteries is a major cause of heart disease. Atherosclerosis occurs when buildup of cholesterol and fat create plaques that thicken the walls of blood vessels causing them to stiffen and become more narrow.

When atherosclerosis is severe, it can weaken the heart in several ways. When it is widespread in arteries throughout the body, the heart must work extra hard to pump the same amount of blood through the now narrower vessels because the space for the blood to move through is smaller. Over the long term, the heart cannot sustain this heavy work load and begins to weaken, leading to the condition known as heart failure.

When atherosclerosis occurs in the vessels that nourish the heart itself, called the coronary arteries, the result is coronary artery disease. This condition results in reduced blood flow to the heart muscle tissue and can cause angina (chest pain) and if the blockage of these arteries is severe, can lead to heart attack (myocardial infarction).