Association of prior β-blocker use and the outcomes of patients with out-of-hospital cardiac arrest

Background β-Blocker therapy is one of the most commonly prescribed treatments for patients with cardiac conditions. In patients with out-of-hospital cardiac arrest (OHCA), however, recent data suggest that prior treatment with β-blockers could be harmful by lowering the incidence of a shockable presenting rhythm. The main objective of our study was to determine the association between prior β-blocker use and mortality in OHCA patients. Methods An observational study was conducted using the Toronto Rescu Epistry database that captured consecutive OHCA patients from 2005 to 2010. Patients older than 65 years with nontraumatic cardiac arrest and attempted resuscitation were included. Patients prescribed β-blockers within 90 days of the arrest were compared with those without such therapy. The primary outcome was all-cause mortality at 30 days. Potential confounders were accounted for by inverse probability of treatment weighting using the propensity score. Results The median age of 8,266 OHCA patients was 79 years, 41% were women, and 2,911 (35.2%) were prescribed a β-blocker prior to cardiac arrest. Patients prescribed β-blockers were more likely to have existing cardiac risk factors and cardiovascular conditions. In the propensity-weighted cohort, there were no differences in the presenting rhythm, with 18.4% of patients in the β-blocker group having a shockable rhythm vs 17.5% in the no β-blocker group (standardized difference .023). In addition, 30-day mortality was not significantly different between patients prescribed β-blockers and no β-blockers (95.6% vs 95.1%, P = .36). Conclusion β-Blocker use was not associated with lower rates of shockable rhythms or mortality among older patients with OHCA.