Sunday, January 15, 2006

myocardial infarction (heart attack)

Myocardial infarction is the rapid death of part of the heart muscle as a result of the sudden blockage of one of the branches of a coronary artery. This blockage may be caused by the formation of a blood clot in the coronary artery, progression of atherosclerotic changes, or prolonged constriction of the arteries. A myocardial infarction may be extensive enough to cause immediate death or it may cause necrosis of a portion of the myocardium (heart muscle) with subsequent healing by scar formation or fibrosis. Heart attack is the major cause of death in people over age 65. Over 2,000 per 100,000 population in the United States suffer heart attacks. Symptoms include chest pain, sweating, nausea, vomiting, cyanosis, shock, decreasing blood pressure, confusion, weakness, and a rapid weak pulse. The pain is described as sudden, severe, crushing, or viselike in the substernal region that may radiate to the neck, jaw, arms, back, or abdomen and lasts longer than 10 minutes. This pain occurs at random and is not associated with effort as angina is. Although pain is the most common symptom, it is not necessarily present. The incidence of painless myocardial infarcts increase with age and in the elderly the chief complaint may be a sudden shortness of breath.
Treatment usually involves hospitalization to resuscitate and stabilize the person. During the acute phase of the myocardial infarction the goal of treatment is to reduce the workload of the heart. Generally, an intravenous route is established and the patient is given morphine sulfate to relieve pain and apprehension, and to produce dilation of the blood vessels. The person is placed on bed rest for 24 to 48 hours in order to limit the size of the infarction. Rest and reassurance are essential. Sometimes, sedation with Valium or an equivalent is necessary to achieve this. Ventricular fibrillation is one of the most serious threats during an myocardial infarction. Because of this, the person should be constantly monitored with EKG and frequent vital signs. If premature ventricular beats (PVBs) are documented, intravenous lidocaine is usually administered. Oxygen therapy is administered for 24 hours or until symptoms resolve to correct a decrease in arterial oxygen pressure caused by ventilation-perfusion abnormalities. Anticoagulation therapy mayor may not be administered. Some physicians feel it might be beneficial to give intravenous heparin until the patient is ambulating well.
A soft, low-salt diet is recommended for the first few days following a myocardial infarction. A stool softener should be given since the intense straining may trigger arrhythmias, cardiac arrest, or pulmonary embolus. The clot may be dissolved, in some cases, with streptokinase (an enzyme). Some people may benefit from balloon dilation of the coronary blockage. If these methods are not useful, coronary bypass surgery may be necessary.
Coronary bypass surgery involves bypassing an obstructed area of the coronary vessels with a graft or artificial substitute. During hospitalization a rehabilitation program will begin. Progressive activity is closely monitored. If cyanosis (blueness of the skin), arrhythmias, resting heart rate greater than 100, or resting blood pressure greater than 160/95 during an exercise session are present, the session should be terminated. After discharge from the hospital the person is usually put on a gradually increasing walking program. Education is an important part of the treatment for myocardial infarction patient. The education program should include an individualized presentation of risk factors, medications, diet, and it should stress the importance of gradual progressive activity. Contrary to a common myth, a person can resume sexual intercourse following a myocardial infarction. In general, the person should abstain from intercourse for four to six weeks. If the person can walk two flights of stairs without cardiac difficulties he or she is generally able to perform sexual intercourse safely.
Myocardial infarction is a serious event and one of the major causes of death among the elderly. Many people, however, live an active and comfortable life for years following a myocardial infarction.
Phipps, W. J., et al. Medical Surgical Nursing. St. Louis: C. V. Mosby Co., 1983.
Scherer, J. C. Introductory Medical-Surgical Nursing. Philadelphia: J. B. Lippincott Co., 1982.

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