A survey of the literature concerning 20 years' experience of β-blockade after myocardial infarction indicates that several positive effects are achieved and that these are neither marginal nor transient. Mortality is reduced during the first year from about 10 to 7%. This has been shown for the individual β-blockers metoprolol, propranolol, and timolol, and also when the data on all β-blocker trials have been pooled. The effect is further enhanced if therapy continues. Patients at high risk of mortality can be separated fairly accurately from those at low risk. Thus, prophylactic treatment with the sole purpose of reducing mortality can be individualized. Effects on reinfarction are also already present after 1 year and are enhanced during further follow-up. It has not yet been possible, however, to identify those patients in whom this end-point will not be influenced. Furthermore, during extended follow-up, the proportion of asymptomatic patients who are free of side effects increases during treatment with β-blockade, whereas it decreases during placebo therapy, due mostly to increased numbers of patients suffering from complications such as reinfarction, angina pectoris, cerebrovascular incidents, arrhythmias, or disturbances in the peripheral circulation. Twenty percent of patients experienced improved fitness when β-blockade treatment was withdrawn, which balances the beneficial effects. No other drugs have been shown to have comparable beneficial effects. We conclude that the practical implications of the clinical trials indicate that β-blockade should be continued for at least 3 years after myocardial infarction in patients without severe side effects.
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