Do β-blockers reduce short-term mortality following acute myocardial infarction? A systematic review and meta-analysis

Objective: Acute myocardial infarction (AMI) remains a major cause of death and beta-blockers are known to reduce long-term mortality in post-AMI patients. We sought to determine whether patients receiving beta-blockers acutely (within 72 h) following AMI had a lower mortality rate at 6 weeks than patients receiving placebo. Methods: We conducted a systematic review of randomized controlled clinical trials that assessed 6-week mortality and compared beta-blockers with placebo in patients randomized within the first 72 hours following AMI. We searched these databases: MEDLINE (1966-2006), EMBASE (1980-2007), Cochrane Central Register of Controlled Trials, Health Star (1966-2007), Cochrane Database for Systematic Reviews, ACP Journal Club (1991-2007), Database of Abstracts of Reviews of Effect (< 1st quarter 2007) and Conference Papers Index (1984-2007). Two blinded reviewers extracted the data and rated study quality using the Jadad score and the adequacy of allocation concealment score, which was adopted by the Cochrane group. We calculated pooled odds ratios (ORs) using a random effect model and performed sensitivity analyses to explore the stability of the overall treatment effect. Results: We included 18 studies (13 were rated high-quality) with 74 643 enrolled participants and had 5095 deaths. Compared with placebo, adding beta-blockers to other interventions within 72 hours after AMI did not result in a statistically significant reduction in 6-week mortality (OR 0.95, 95% confidence interval [CI] 0.90-1.01). When restricted to high quality studies, the OR for 6-week mortality reduction was 0.96 (95% CI 0.91-1.02). We found similar results including studies that enrolled patients within 24 hours after AMI. However, a subgroup analysis that excluded high-risk patients with Killip class III and above showed that beta-blockers resulted in a significant reduction in short-term mortality (OR 0.93, 95% CI 0.88-0.99). Conclusion: Acute intervention with beta-blockers does not result in a statistically significant short-term survival benefit following AMI but may be beneficial for low-risk ( Killip class I) patients.