Background: Biphasic waveform defibrillation results in higher rates of termination of fibrillation than monophasic waveform defibrillation but has not been shown to improve survival outcomes.
Objective: To compare the effectiveness of a biphasic automated external defibrillator (AED) with a monophasic AED for witnessed out-of-hospital cardiac arrest (OHCA) due to ventricular fibrillation (VF).
Methods: In a prospective population-based cohort study, adults with witnessed VF OHCA were treated with either monophasic or biphasic waveform AED shocks. The primary outcome measure was neurologically favourable 1-month survival, defined as a Cerebral Performance Categories score of 1 or 2.
Results: Of 366 adults with witnessed OHCA of presumed cardiac aetiology, 74 (20%) had VF. Termination of VF with the first shock tended to occur more frequently after biphasic AED shocks (36/44 (82%) vs 20/30 (67%), p = 0.14). Return of spontaneous circulation (ROSC) occurred more frequently after biphasic AED shocks (29/44 (66%) vs 8/30 (27%), p = 0.001). Neurologically favourable 1-month survival was also more frequent in the biphasic group (10/44 (23%) vs 1/30 (3%), p = 0.04). The median time interval from the first shock to the second shock was 67 s in the monophasic group and 24 s in the biphasic group (p = 0.001).
Conclusions: Treatment with biphasic AED shocks improved the likelihood of ROSC and neurologically favourable 1-month survival after witnessed VF compared with monophasic AED shocks. In addition to waveform differences, a shorter time interval from the first shock to the second shock could account for the better outcomes with biphasic AED.
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Funding: This study was supported by Grant-in-Aid for University and Society Collaboration, Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports, and Culture, Japan (No 11794023, 19390459) and Health and Labor Science Research Grant for Cardiovascular Diseases (14C-7), H16-Shinkin-02, Comprehensive Research on Cardiovascular Diseases, and Research on Medical Safety and Health Technology Assessment from the Japanese Ministry of Health, Labor and Welfare.
Competing interests: None.
Ethics approval: The research was approved by the institutional review board of Osaka University with the assent of the EMS authorities and local governments in Osaka prefecture.
The primary authors had full access to and take responsibility for the integrity of the data. All authors have read and agreed the manuscript as written.