Epidemiology Research Today is a free monthly online journal that collates and summarizes the latest research about Epidemiology, including details on twin studies, statistics, environmental and genetic factors.

Beta-blocker use and the changing epidemiology of out-of-hospital cardiac arrest rhythms.

Youngquist ST, Kaji AH, Niemann JT

Department of Emergency Medicine, Harbor-UCLA Medical Center, Torrance, CA 90590, United States.

BACKGROUND: The incidence of ventricular fibrillation (VF) as the presenting rhythm in out-of-hospital cardiac arrest (OHCA) is declining, whereas pulseless electrical activity (PEA) is increasing. This changing epidemiology has occurred concomitant with an increase in beta-blocker use. AIMS: The aim of this study was to measure the association of beta-blocker use among prehospital cardiac arrest patients with PEA versus VF as presenting rhythm. MATERIALS AND METHODS: In this retrospective cohort study, records of all OHCA patients presenting to a single municipal hospital between 1 January 2001 and 31 December 2006 were reviewed. Age, sex, race, first documented rhythm, estimated down time, presence of bystander CPR, return of spontaneous circulation, beta-blocker use, and comorbid illnesses were noted. A Mantel-Haenzel chi-square was computed to describe the association between beta-blocker use and PEA, compared to beta-blocker use and VF. A sensitivity analysis was also performed to account for missing data, misclassification of beta-blocker use, misclassification of initial rhythm, confounding by unknown factors, and random error. RESULTS: After exclusion of patients with asystole and patients in whom beta-blocker use was unclear/unknown, a cohort of 179 arrests was evaluated. The odds ratio for beta-blocker use among PEA versus VF patients was 3.7 (95% CI 1.9-7.2), and probabilistic adjustment for exposure and outcome misclassification, confounding, and random error increased the odds ratio to 5.0 (95% CI 1.1-31.0). CONCLUSIONS: There appears to be an association between beta-blockers and the changing epidemiology of arrest rhythms, which may account for the increasing incidence of PEA and concomitant decrease in VF.

Published 11 February 2008 in Resuscitation, 76(3): 376-80.
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