Heart Attack and Acute Coronary Syndrome

Introduction

The heart is the human body's hardest working organ. Throughout life it continuously pumps blood enriched with oxygen and vital nutrients through a network of arteries to all tissues of the body. To perform this strenuous task, the heart muscle itself needs a plentiful supply of oxygen-rich blood, provided through a network of coronary arteries. These arteries carry oxygen-rich blood to the heart's muscular walls (the myocardium).

A heart attack (myocardial infarction) occurs when blood flow to the heart muscle is blocked, and tissue death occurs from loss of oxygen, severely damaging a portion of the heart.

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Coronary Artery Disease. Coronary artery disease causes nearly all heart attacks. Coronary artery disease is the end result of a complex process called atherosclerosis (commonly called "hardening of the arteries"). This causes blockage of arteries (ischemia) and prevents oxygen-rich blood from reaching the heart. [For more information, see In-Depth Report #3: Coronary artery disease.]

Click the icon to see an image of atherosclerosis.

Heart Attack

Heart attack (myocardial infarction) is among the most serious outcome of atherosclerosis. It can occur as a result of one of two effects of atherosclerosis:

• If the plaque develops fissures or tears. Blood platelets adhere to the site to seal off the plaque, and a blood clot (thrombus) forms. A heart attack can then occur if the blood clot completely blocks the passage of oxygen-rich blood to the heart.
• If the artery becomes completely blocked after gradual buildup of plaque due to atherosclerosis. Heart attack may occur if not enough oxygen containing blood can flow through this blockage.

Click the icon to see an image of an acute myocardial infarction.

Angina

Angina, the primary symptom of coronary artery disease, is typically experienced as chest pain. There are two kinds of angina:

• Stable Angina. This is predictable chest pain that can usually be managed with lifestyle changes and medications, such as low-dose aspirin and nitrates.
• Unstable Angina. This situation is much more serious than stable angina, and is often an intermediate stage between stable angina and a heart attack. Unstable angina is part of a condition called acute coronary syndrome.