Causes, Risk Factors, Symptoms

A heart attack, or myocardial infarction, occurs when an area of the heart muscle is damaged or dies because a coronary artery (an artery that delivers blood to the heart muscle itself) has been blocked and the oxygen-rich blood supply to that area of the heart has been drastically reduced. The damaged muscle tissue of the heart is replaced with scar tissue, which does not function as muscle but rather as a kind of patch. When the area of damage is large enough, the ability of the heart to pump blood can be seriously diminished.

Although the chances of surviving a heart attack are now better than ever and complete recovery is common, heart attack is still the number one cause of death in the United States. Heart attacks that do not result in death may lead to serious complications, including shock, cardiac arrhythmia (irregularity of the heartbeat), and congestive heart failure, in which the heart is not able to pump enough blood to meet the needs of the body.

Heart attack is damage to the heart muscle stemming from blocked or clogged arteries.

A heart attack occurs when an area of the heart
 is damaged or dies because the coronary artery
supplying the area has been blocked by a
blood clot or advanced atherosclerosis.

Causes

Heart attack is caused by the blockage of a coronary artery by a thrombus (blood clot) or by atherosclerosis, a disease in which the arteries become clogged by fatty deposits that can rupture and obstruct the artery. Damage to the heart muscle occurs when the narrowed coronary arteries are unable to deliver the extra oxygenated blood needed by the heart during emotional stress or physical exertion.

Risk Factors

A number of factors have been associated with an increased risk of heart attack, including diabetes and a family history of heart disease. Hypertension (high blood pressure) increases the resistance in the blood vessels, forcing the heart to pump harder to push blood through the body. Smoking constricts and damages the arteries and reduces blood flow to the heart muscle. Stress increases the oxygen requirement of the heart muscle.

A diet high in saturated fats (fats that are usually solid at room temperature, including those animal fats found in butter and meats) has been found to increase the serum cholesterol level in the blood and thus the chances of developing atherosclerosis. The lack of moderate, regular exercise results in poor tone of the heart muscle and may also prevent the development of collateral circulation (a system of smaller blood vessels that bypass a blocked artery and increase the blood supply to the area served by that artery). Cocaine, taken by inhalation or intravenously, can cause heart attacks and is a common cause of heart attacks in young people who are otherwise healthy.

Symptoms

The major symptom of a heart attack is a crushing pain in the middle of the chest, behind the breastbone; the pain can also extend down one or both arms and into the neck, back, teeth, or jaws. Fatigue, heavy perspiration, dizziness, difficulty in breathing, and fever may accompany this pain. The pain may be somewhat similar to that due to angina pectoris, but the pain of a heart attack is more intense, will not be relieved by nitroglycerin, and will not go away within a few minutes, as angina pain will. Also, a heart attack can take place during sleep, which is uncommon for angina pain.

Heart attacks may be very mild, signaled only by slight discomfort, faintness, and nausea. In very serious cases, a heart attack may be accompanied by cardiac arrest (cessation of the heartbeat) or ventricular fibrillation (degeneration of the normal, steady heartbeat to a useless quivering that prevents blood from being pumped through the body).

In the next section, we'll review the important factors needed for a proper diagnosis and such treatment techniques as cardiopulmonary resuscitation for someone experiencing a heart attack.