Primary and secondary prevention of myocardial infarction and strokes
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AIM: To summarize the risk factors associated with coronary heart disease and strokes and to evaluate measures used in the prevention and treatment of these diseases. METHOD: A review of the results of randomly allocated clinical trials of treatment for both primary and secondary prevention of coronary heart disease and strokes. RESULTS: Reductions in elevated blood pressure and cholesterol and cessation of cigarette smoking have clearly been shown to reduce the incidence of coronary heart disease. A reduction in blood pressure has also been shown to reduce the risk of strokes. In addition to other classical risk factors, such as abnormal serum lipids, diabetes and a genetic predisposition, recent studies have shown that elevated levels of fibrinogen and other clotting factors, elevated levels of renin and decreased levels of anti-oxidant vitamins such as E, C and beta-carotene can predict coronary heart disease and strokes. Thrombolytic therapy, aspirin and beta-blockers have been shown to reduce mortality in patients with myocardial infarction, and the latter two agents reduce mortality, re-infarction and strokes with long-term use. Treatment with intravenous magnesium and nitrates has shown promise but larger trials are required to confirm the results. Both aspirin and heparin have proven value in reducing the incidence of myocardial infarction and death in unstable angina. Following an acute myocardial infarction, long-term therapy with aspirin, beta-blockers, lipid-lowering agents and oral anticoagulants has been shown to reduce mortality and re-infarction. In patients with large infarcts associated with a low ejection fraction or heart failure, the use of angiotensin converting enzyme (ACE) inhibitors reduces mortality, hospitalization for heart failure and re-infarction. The use of diuretics to lower blood pressure reduces strokes. In contrast, calcium antagonists do not appear to consistently reduce mortality or prevent vascular events when used for primary or secondary prevention of either myocardial infarction or strokes. CONCLUSIONS: Myocardial infarction and strokes can be prevented by refraining from smoking and maintaining appropriate blood pressure levels and a favourable balance of lipids. Following a myocardial infarction, further drug treatment should include aspirin, thrombolytic therapy (in acute myocardial infarction), beta-blockers, ACE inhibitors (in patients with a low ejection fraction) and perhaps anticoagulants.
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