heart, right

heart attack A sudden blockage of a coronary artery. Not infrequently, this leads to the death of part of the heart muscle due to its loss of blood supply. Typically, the loss of blood supply is caused by a complete blockage of a coronary artery by a blood clot. The interruption of blood flow is usually caused by arteriosclerosis, with narrowing of the coronary arteries, the culminating event being a thrombosis (clot). Death of the heart muscle often causes chest pain and electrical instability of the heart muscle tissue. Electrical instability of the heart may cause ventricular fibrillation (chaotic electrical disturbance), resulting in the inability of the heart to deliver oxygenated blood to the body. Permanent brain damage and death can result from heart attack unless oxygenated blood flow is restored within 5 minutes. Heart attack deaths can be avoided if a bystander starts CPR (cardiopulmonary resuscitation) within 5 minutes of the onset of ventricular fibrillation. 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 after a heart attack. Also known as a myocardial infarction (MI). See also cardiac arrest.