beta Blockade after myocardial infarction: systematic review and meta regression analysis

Objectives To assess the effectiveness of beta blockers in short term treat ment for acute myocardial infarction and in longer term secondary preventio n; to examine predictive factors that may influence outcome and therefore c hoice of drug; and to examine the clinical importance of the results in the light of current treatment. Design Systematic review of randomised controlled trials. Setting Randomised controlled trials. Subjects Patients with acute or past myocardial infarction. Intervention beta Blockers compared with control. Main outcome measures All cause mortality and non-fatal reinfarction. Results Overall, 5477 of 54 234 patients (10.1%) randomised to beta blocker s or control died. We identified a 23% reduction in the odds of death in lo ng term trials (95% confidence interval 15%, to 31%), but only a 4% reducti on in the odds of death in short term trials (-8% to 15%). Meta regression in long term trials did not identify a significant reduction in effectivene ss in drugs with cardioselectivity but did identify a near significant tren d towards decreased benefit in drugs with intrinsic sympathomimetic activit y. Most evidence is available for propranolol timolol, and metoprolol. In l ong term trials, the number needed to treat for 2 years to avoid a death is 42, which compares favourably with other treatments for patients with acut e or past myocardial infarction. Conclusions beta Blockers are effective in long term secondary prevention a fter myocardial infarction, but they are underused in such cases and lead t o avoidable mortality and morbidity.