Impact of community-wide deployment of biphasic waveform automated external defibrillators on out-of-hospital cardiac arrest in Taipei

Patrick Chow-In Ko, Matthew Huei-Ming Ma, Zui-Shen Yen, Chung-Liang Shih, Wen-Jone Chen, Fang-Yue Lin
Resuscitation 2004, 63 (2): 167-74

OBJECTIVES: To determine the impact and outcome of out-of-hospital cardiac arrests (OHCA) while using automated external defibrillators (AED) with biphasic waveforms and its effectiveness when using the Utstein Style community-wide in Taipei.

MATERIAL AND METHODS: A one-year study was conducted to collect OHCA patients with AED utilization prospectively in Taipei City. All events and variables were recorded in the Utstein Style. Electrocardiography and voice records recovered from AED data cards were analysed. The endpoints were survival outcomes.

RESULTS: Of 653 OHCA patients with AED utilization, only 80 (12.6%) patients with 635 true arrests presented with ventricular fibrillation or tachycardia (VF/VT) as the initial rhythm. The interval between call-to-shock was 5 min longer than call-to-EMS arrival (9.3 min versus 4.0 min). Fourteen (25%) of the 55 witnessed VF/VT arrests survived to home discharge. Ninety-seven percent of shockable rhythms were successfully terminated with less than three shocks. For all OHCA patients, initial rhythm of VF/VT (OR 3.4; 95% CI = 1.2-9.4), witnessed status (OR 4.7; 95% CI = 1.3-16.6), and presence of organised rhythm irrespective of pulse during prehospital resuscitation (OR 9.2; 95% CI = 3.2-26.8) demonstrated an independent association with survival to home discharge. For VF/VT arrests, witnessed status, shorter call-to-shock time, high successful rate of the first shock, fewer averaged number of shocks delivered for each patient, and presence of an organised rhythm during prehospital resuscitation showed a likelihood to predict to predict discharged survival in univariate analysis.

CONCLUSIONS: Low frequency of VF arrests is unique to certain eastern populations but without a reduction of AED shock efficacy with biphasic waveform. Besides initial VF and witnessed status, a prehospital post-shock organized rhythm irrespective of pulse appears to be correlated to survival. Certain circumstances in a congested metropolitan city consume time to deliver shocks even after EMS arrival, and might require bystander or public access defibrillation.

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