Effects of Interrupting Precordial Compressions on the Calculated Probability of Defibrillation Success During Out-of-Hospital Cardiac Arrest

TLDR

CPR generates ECG artifacts, requiring a mandatory pause for rhythm analysis, and longer hands‑off intervals have been shown to lower return of spontaneous circulation in animal studies. This study examined whether similar hands‑off intervals in human ventricular fibrillation patients alter ECG‑derived probabilities of ROSC. The authors continuously estimated ROSC probability from ECG features during up to 20 seconds of 634 hands‑off intervals in VF patients. When the initial ROSC probability was high or moderate, it fell to a median of 8–11 % after 20 seconds, whereas low initial probabilities remained unchanged, underscoring the need to minimize the pause before shock.

Abstract

Background — Cardiopulmonary resuscitation (CPR) creates artifacts on the ECG and, with automated defibrillators, a pause in CPR is mandatory during rhythm analysis. The rate of return of spontaneous circulation (ROSC) is reduced with increased duration of this hands-off interval in rats. We analyzed whether similar hands-off intervals in humans with ventricular fibrillation causes changes in the ECG predicting a lower probability of ROSC. Methods and Results — The probability of ROSC after a shock was continually determined from ECG signal characteristics for up to 20 seconds of 634 such hands-off intervals in patients with ventricular fibrillation. In hands-off intervals with an initially high (40% to 100%) or median (25% to 40%) probability for ROSC, the probability was gradually reduced with time to a median of 8% to 11% after 20 seconds ( P <0.001). In episodes with a low initial probability (0% to 25%; median, 5%), there was no further reduction with time. Conclusions — The interval between discontinuation of chest compressions and delivery of a shock should be kept as short as possible.