Background: To assess the influence of beta2-receptor suppression on top of selective beta1-receptor blockade on the occurrence of vascular events and on all-cause mortality in patients with acute coronary syndrome (ACS) or heart failure (HF ).
Methods: Systematic review of studies published since 1980. Randomised controlled trials directly comparing beta1 blockers with beta1+2 blockers, or comparing the two beta blockers with placebo, were included. Studies had a minimum treatment period of three months and total mortality or vascular events as their primary or secondary outcome.
Results: Of the included studies, five directly compared beta blockers (3733 patients) and 28 compared beta blockers with placebo (30,889 patients). These latter studies were heterogeneous in study population, dose and type of beta blockers. In ACS, the only study directly comparing different beta blockers was underpowered to detect a difference on mortality, while in HF beta1+2 blockers significantly decreased mortality compared with b1 blockers (RR 0.86, 95% confidence interval 0.78 to 0.94). In ACS, beta1 blockers in placebo-controlled trials non-significantly reduced total mortality (RR 0.82, 0.67 to 1.01) or vascular events (RR 0.68, 0.42 to 1.11), while beta1+2 blockers were associated with a significant decrease in total mortality (RR 0.73, 0.64 to 0.82), and vascular events (RR 0.71, 0.59 to 0.84). In HF, beta1 and beta1+2 blockers reduced total mortality, while only beta1+2 blockers decreased vascular events (RR 0.80, 0.64 to 1.00).
Conclusions: Additional beta2-receptor blockade may be more effective than beta1-receptor blockade alone in preventing total mortality and vascular events in patients with ACS or, to a lesser extent, HF . However, only a few studies directly compared beta blockers, and indirect comparisons were subject to heterogeneity, which weakens firm conclusions.