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

Background — Beta-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 prior treatment with beta-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 beta-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 non-traumatic cardiac arrest and attempted resuscitation were included. Patients prescribed beta-blockers within 90 days of the arrest were compared to 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 beta-blocker prior to cardiac arrest. Patients prescribed beta-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 beta-blocker group having a shockable rhythm versus 17.5% in the no beta-blocker group (standardized difference 0.023). In addition, 30-day mortality was not significantly different between patients prescribed beta-blockers and no beta-blockers (95.6% vs. 95.1%, p = 0.36).

Conclusion — Beta-blocker use was not associated with lower rates of shockable rhythms or mortality among older patients with OHCA.