Your heart muscle needs oxygen to survive. A heart attack occurs when the blood flow that brings oxygen to the heart muscle is severely reduced or cut off completely (View an animation of blood flow). This happens because coronary arteries that supply the heart muscle with blood flow can slowly become narrrow from a buildup of fat, cholesterol and other substances that together are called plaque. This slow process is known as atherosclerosis . When a plaque in a heart artery breaks, a blood clot forms around the plaque. This blood clot can block the blood flow through the heart muscle. When the heart muscle is starved for oxygen and nutrients, it is called ischemia. When damage or death of part of the heart muscle occurs as a result of ischemia, it is called a heart attack or myocardial infarction (MI). About every 34 seconds, someone in the United States has a myocardial infarction (heart attack).

Your heart muscle needs oxygen to survive. A heart attack occurs when the blood flow that brings oxygen to the heart muscle is severely reduced or cut off completely (View an animation of blood flow). This happens because coronary arteries that supply the heart muscle with blood flow can slowly become narrrow from a buildup of fat, cholesterol and other substances that together are called plaque. This slow process is known as atherosclerosis . When a plaque in a heart artery breaks, a blood clot forms around the plaque. This blood clot can block the blood flow through the heart muscle. When the heart muscle is starved for oxygen and nutrients, it is called ischemia. When damage or death of part of the heart muscle occurs as a result of ischemia, it is called a heart attack or myocardial infarction (MI). About every 34 seconds, someone in the United States has a myocardial infarction (heart attack).

Atherosclerosis has no symptoms. One reason there may be no warning signs is that sometimes when a coronary artery becomes narrowed, other nearby vessels that also bring blood to the heart sometimes expand to help compensate. The network of expanded vessels is called collateral circulation and helps protect some people from heart attacks by getting needed blood to the heart. Collateral circulation can also develop after a heart attack to help the heart muscle recover.

When a heart attack occurs, the heart muscle that has lost blood supply begins to suffer injury. The amount of damage to the heart muscle depends on the size of the area supplied by the blocked artery and the time between injury and treatment. Damage to the heart muscle from a heart attack heals by forming scar tissue. It usually takes several weeks for your heart muscle to heal. The length of time depends on the extent of your injury and your own rate of healing. The heart is a very tough organ. Even though a part of it may have been severely injured, the rest keeps working. But because your heart has been damaged, it may be weaker and can't pump as much blood as usual. However, with proper treatment after a heart attack and lifestyle changes, further damage can be limited or prevented. Learn more about heart damage detection.

The answer is most likely yes. The heart muscle begins to heal soon after a heart attack and usually takes about eight weeks. Scar tissue may form in the damaged area, and that scar tissue does not contract or pump as well as healthy muscle tissue. That means that extent of damage to the heart muscle can impact how well the heart pumps blood throught the body. The degree of loss of function depends on the size and location of the scar tissue. Most heart attack survivors have some degree of coronary artery disease (CAD) and will have to make important lifestyle changes and possibly take medication to prevent a future heart attack and lead a full, productive life.

Learn more about diseases and conditions that affect your heart.

Learn more about recovering from heart attack.

No. One very common type of chest pain is called angina, or angina pectoris. It's a recurring discomfort that usually lasts only a few minutes. Angina occurs when your heart muscle doesn't get the blood supply and oxygen that it needs. The difference between angina and a heart attack is that angina attacks don't permanently damage the heart muscle. Often angina occurs during exercise or emotional stress when your heart rate and blood pressure increase and your heart muscle needs more oxygen. Learn about unstable angina.

Myocardial infarction – The damaging or death of an area of the heart muscle (myocardium) resulting from a blocked blood supply to that area; medical term for a heart attack.

Coronary thrombosis – Formation of a clot in one of the arteries that conduct blood to the heart muscle. Also called coronary occlusion.

Coronary occlusion – An obstruction of a coronary artery that hinders blood flow to some part of the heart muscle. A cause of heart attack.

Sometimes a coronary artery temporarily contracts or goes into spasm. When this happens the artery narrows and blood flow to part of the heart muscle decreases or stops. We're not sure what causes a spasm. A spasm can occur in normal-appearing blood vessels as well as in vessels partly blocked by atherosclerosis. A severe spasm can cause a heart attack.

No. But a heart attack can cause a cardiac arrest. Heart attacks are caused by a blockage that stops blood flow to the heart. Cardiac arrest is caused when the heart's electrical system malfunctions. In cardiac arrest (also called sudden cardiac death or SCD), death results when the heart suddenly stops working properly. This is caused by abnormal, or irregular, heart rhythms (called arrhythmias). The most common arrhythmia in cardiac arrest is ventricular fibrillation. This is when the heart's lower chambers suddenly start beating chaotically and don't pump blood. Death occurs within minutes after the heart stops. Cardiac arrest may be reversed if CPR (cardiopulmonary resuscitation) is performed and a defibrillator is used to shock the heart and restore a normal heart rhythm within a few minutes.