The causes of heart disease are as varied as the types of heart disease. Some of the most common causes of heart disease include atherosclerosis ("hardening of the arteries"), changes in the electrical activity of the heart, birth defects, and infections. Here are some common types of heart disease and their causes.

Coronary artery disease (CAD) is associated with atherosclerosis ("hardening of the arteries"). Atherosclerosis is caused by the build-up of plaque, which is made of cholesterol and other substances, along the walls of the arteries. Angina (chest pain) occurs when the heart is receiving less oxygen than it needs to work normally. This is caused by narrowing of arteries lined with plaque and cholesterol, reducing the amount of blood reaching a particular area of the heart. If plaque in an artery ruptures, the body forms a blood clot to repair the damage. The clot can block an artery to the heart and cause a heart attack.

Arrhythmia may occur because the special nerve cells that produce the electrical signals of the heart (telling the heart when to pump) don't work properly or the signals are in some way being blocked, slowed down, sped up, or forced to move in a different path. Arrhythmias can also occur when another part of the heart starts to produce electrical signals, adding to the signals from the special nerve cells and disrupting the normal heartbeat.

Heart failure is caused by conditions that weaken the heart or affect its ability to pump blood. Coronary artery disease, heart attack, high blood pressure, diabetes, heart valve disease, heart enlargement, abnormal heart structures caused by inherited disease, and severe lung disease are all possible causes of heart failure.

Heart valve disease can either be present at birth or be acquired after birth. When heart valve disease is present at birth, it is referred to as congenital heart valve disease and usually involves the aortic or pulmonic valve. Heart valve disease that occurs later in life can be caused by infections such as rheumatic fever or endocarditis (infection of the heart valves), heart attack, high blood pressure, and heart muscle disease.

Heart muscle disease or cardiomyopathy can be caused by viral infections of the heart muscle (myocarditis), genetics, radiation, or connective tissue disorders (e.g., amyloidosis). In some cases, there is no known caused of the heart muscle disease.

Congenital heart disease is a type of birth defect that causes problems with the heart at birth. For most people, the cause of congenital heart disease is unknown.