Heart Attack 2

What is angina pectoris?

Angina pectoris is chest pain or pressure that occurs when the oxygen supply to the heart muscle cannot keep up with oxygen consumption by the heart muscle. (Oxygen consumption by the heart muscle increases with physical exertion or excitement and decreases with rest and relaxation.) Most commonly, the inadequate supply of oxygen is due to narrowing of the coronary arteries by atherosclerosis. When coronary arteries are narrowed by more than 50% to 70%, the arteries cannot increase the supply of blood to the heart muscle during exertion or other periods of high oxygen demand. An insufficient supply of oxygen to the heart muscle causes chest pain (angina). Chest pain that occurs with exercise or exertion is called exertional angina. Please read the MedicineNet Angina article for more information on the different types of angina.

What is a heart attack?

A heart attack (myocardial infarction) is the death of heart muscle due to the sudden and complete blockage of a coronary artery by a blood clot. A coronary artery blockage usually occurs in arteries that contain cholesterol plaques. A plaque can rupture and initiate the formation of a blood clot next to it. A blood clot can completely block blood flow through a coronary artery and deprive the heart muscle of needed nutrients and oxygen. The heart muscle then dies, which produces a heart attack. For additional information, please read the Heart Attack article, and the Heart Attack Photo Essay, with real pictures of coronary artery blockage.

Ventricular fibrillation

A heart attack can trigger the sudden onset of ventricular fibrillation. Ventricular fibrillation is a chaotic electrical rhythm of the heart that causes cardiac arrest (the heart stands still and ceases to pump blood). Ventricular fibrillation causes permanent brain damage and death unless a normal heartbeat can be restored within five minutes of its onset. Of the 1 million Americans who suffer heart attacks annually, approximately 400,000 of them die suddenly and unexpectedly from ventricular fibrillation before the victims can reach any medical assistance. For these people, the first sign of coronary heart disease is sudden, unexpected death.