Heart attack

Heart attack: The death of heart muscle due to the loss of blood supply. The loss of blood supply is usually caused by a complete blockage of a coronary artery, one of the arteries that supplies blood to the heart muscle. Death of the heart muscle, in turn, causes chest pain and electrical instability of the heart muscle tissue.

The electrical instability of the heart causes ventricular fibrillation (chaotic electrical disturbances affecting the ventricles, the lower chambers of the heart). Orderly transmission of electrical signals in the heart is important for the regular beating (and the efficient pumping) of the heart. A heart undergoing ventricular fibrillation simply quivers and can not pump or deliver oxygenated blood to the brain. Permanent brain damage and death can occur unless oxygenated blood flow is restored within five minutes.

Many heart attack deaths are due to ventricular fibrillation that occurs before the victim can reach any medical assistance or the emergency room. These electrical disturbances of the heart can often be successfully treated with medications or other means by paramedics in the "field," or upon arrival to the hospital. Approximately 90-95% of heart attack victims who reach the hospital survive. The 5-10% who later die are those who have suffered major heart muscle damage, or who suffer an "extension" or enlargement of their heart attack.

Early heart attack deaths can be avoided if a bystander starts CPR (cardiopulmonary resuscitation) within five minutes of the onset of ventricular fibrillation. CPR involves breathing for the victim and applying external chest compression to make the heart pump. When paramedics arrive, medications and/or electrical shock (cardioversion) to the heart can be administered to convert ventricular fibrillation to a normal heart rhythm. Therefore, prompt CPR and rapid paramedic response can improve the survival chances from a heart attack.

The treatment of a heart attack may include the prompt administration of drugs to dissolve and prevent blood clots; an angioplasty or intracoronary stenting to open an obstructed artery; and medications that open (dilate) blood vessels. Early reopening of a blocked coronary artery reduces the amount of heart muscle damage, lessens the size of the heart attack, and improves prognosis. Patients suffering a heart attack are usually hospitalized for several days to detect heart rhythm disturbance, and observe for shortness of breath and chest pain.

A heart attack is also called a myocardial infarction or an MI. Myocardial refers to the myocardium, the heart muscle. Infarction is tissue death due to a local lack of oxygen.

MedTerms (TM) is the Medical Dictionary of MedicineNet.com.
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