Association between ventricular fibrillation amplitude immediately prior to defibrillation and defibrillation success in out-of-hospital cardiac arrest.

BACKGROUND

Several characteristics of the ventricular fibrillation (VF) waveform during cardiac arrest are associated with defibrillation success, including peak amplitude in the seconds prior to defibrillation. It is not known if immediate pre-defibrillation amplitude is associated with successful defibrillation, return of spontaneous circulation (ROSC) or survival to hospital discharge (SHD).

METHODS

We analyzed automated external defibrillation recordings of 80 patients with out-of-hospital VF cardiac arrest who received 284 defibrillations. We recorded the maximum amplitude during 3-second ECG tracings prior to each defibrillation attempt and the amplitude immediately prior to defibrillation.

RESULTS

Both the amplitude just prior to defibrillation and the highest amplitude within 3 seconds of the defibrillation were significantly higher in successful vs unsuccessful defibrillations (0.21 vs 0.11 mV, P = <.0001 and 0.51 vs 0.36 mV, P = <.0001). Amplitude immediately prior to defibrillation and maximal amplitude within 3 seconds of defibrillation were also higher in defibrillations with ROSC vs. defibrillations without ROSC (0.23 vs. 0.12 mV, P < .0001; and 0.52 vs. 0.38 mV, P < .0001). In defibrillations that resulted in SHD, immediate pre-defibrillation amplitude and maximum amplitude were also significantly larger (0.20 vs. 0.11 mV, P < .0001; and 0.52 vs. 0.35 mV, P < .0001). Binary logistic regression including both measures showed that only immediate pre-defibrillation amplitude remained significantly associated with ROSC while maximal amplitude did not (P = .006 and P = .135).

CONCLUSIONS

Amplitude of the VF waveform at the moment of defibrillation has a strong association with successful defibrillation, ROSC, and SHD.