Background: Ventricular fibrillation (VF) is treated optimally with a defibrillation shock shortly after patient collapse, but may benefit from initial cardiopulmonary resuscitation (CPR) if the shock is delayed. An objective measure of potential responsiveness to defibrillation could help decide optimal initial therapy.
Methods and results: a new electrocardiogram (ECG) analysis algorithm was compared with response interval (call-to-shock) for prediction of patient outcome in a population of 87 VF patients in the Rochester, Minnesota area. In a retrospective analysis, both call-to-shock interval (p = 0.009) and ECG analysis (p < 0.001) predicted neurologically intact survival, with ECG analysis the stronger predictor (p = 0.034). When applied to advising initial patient treatment, ECG analysis compared favorably with the call-to-shock interval. Using a 7 min call-to-shock time criterion, 69% of patients would receive shocks first treatment using ECG analysis versus 67% using the call-to-shock interval (p = NS), 94% of survivors would retain successful shocks first treatment versus 85% (p = NS), and 48% of non-survivors receive alternate CPR-first treatment versus 45% (p = NS). Similarly, no significant differences were observed between ECG analysis and call-to-shock interval using an 8 min criterion.
Conclusions: Both call-to-shock interval and a real-time ECG analysis are predictive of patient outcome. The ECG analysis is more predictive of neurologically intact survival. Moreover, the ECG analysis is dependent only upon the patient's condition at the time of treatment, with no need for knowledge of the response interval, which may be difficult to estimate at the time of treatment.