Beta-blockers not associated with lower risk of death after acute MI in patients without heart failure, study finds
The insignificant effect of beta-blockers on survival was also apparent at one month and six months after discharge, as well as in separate analyses of patients with STEMI and NSTEMI.
Beta-blocker use was not associated with lower mortality up to one year after discharge in patients with acute myocardial infarction (MI) but without heart failure (HF), a recent study found.
Researchers used English and Welsh registry data to assess 179,810 patients with acute MI but not HF or left ventricular systolic dysfunction (LVSD) who survived hospitalization between Jan. 1, 2007, and June 30, 2013. They prospectively followed patients to determine the association between beta-blocker use and mortality at one year.
Study results were published online on May 29 by the Journal of the American College of Cardiology.
Of 91,895 patients with ST-segment elevation MI (STEMI), 96.4% received beta-blockers, and of 87,915 patients with non-ST-segment elevation MI (NSTEMI), 93.2% received beta-blockers. Overall, 9,373 deaths (5.2%) occurred in the full cohort. In unadjusted analyses, the one-year mortality rate was lower among patients who received beta-blockers than among those who did not (4.9% vs. 11.2%; P<0.001).
However, in a propensity score analysis including 24 variables (e.g., sex, discharge medications, cardiovascular risk factors), there was no significant difference in mortality between the groups (average treatment effect coefficient, 0.07; 95% CI, −0.60 to 0.75; P=0.827). The average treatment effect represents the absolute difference in survival time in months between beta-blocker treatment and no beta-blocker treatment.
The insignificant effect of beta-blockers on survival was also apparent at one month and six months after discharge, as well as in separate analyses of patients with STEMI and NSTEMI.
The study authors noted limitations, such as how they did not investigate the role of in-hospital beta-blockers and that the registry data were only recorded during hospitalization. Thus, they were unable to capture new HF cases, medication discontinuation rates, or new prescriptions in the year after acute MI.
An accompanying editorial noted that the results should be interpreted with “extreme caution” because of the general limitations inherent to observational studies. The editorialists noted an additional limitation specific to this study: The left ventricular ejection fraction (LVEF) threshold used to define HF/LVSD was less than 30%. “The study thus includes patients with a post-MI LVEF of between 30% and 40%, for whom the clinical benefit of [beta]-blockers is clearly established,” they wrote.
The study should be considered hypothesis-generating and shouldn't change clinical practice, according to the editorialists. “However, this important report highlights the need to reboot the system: the role of [beta]-blockers in post-MI patients without LVSD (LVEF >40%) needs to be evaluated from scratch,” they wrote.