Abstract 11966: Rhythm Changes Following Defibrillation During Resuscitation in Out-of-hospital Cardiac Arrest

Abstract

Introduction: In the treatment of cardiac arrest, immediate resumption of chest compressions is recommended after delivery of defibrillation. However, it is unclear what the optimal timing is to determine presence of an organized rhythm after shock delivery. The purpose of this study was to investigate the dynamic rhythm changes after defibrillation during resuscitation. Methods: A total of 581 shocks from 264 out-of-hospital cardiac arrest patients with ventricular fibrillation (VF) as the first recorded rhythm were included in this study. Post shock rhythms were analyzed every10 seconds after each shock up to 120 seconds. We determined the presence of VF, asystole (AS) and organized rhythm (OR) at each time point. Results: Ten seconds after shock delivery, VF had been terminated in 70.4% cases (N=409). However, 53.5% of these non-VF rhythms were AS (N=219). Rhythm changes occurred in half of all cases (N=274, 47.2%) during the 2 minutes after shock delivery (Figure 1) and 88.3% of these changes occurred within 60 seconds. Of those initially in AS, 62 (28.3%) evolved into OR within 32.4±24.6 seconds and 117 (53.4%) returned to VF after 31.3±19.9 seconds. Of those with OR (N=190), 89 (46.8%) returned to VF 40.2±28.2 seconds later and 6 degenerated to AS (3.2%) after 48.3±41.7 seconds. VF was recurred in 50.4% (N=206) non-VF rhythms but there were no post-shock rhythm changes in patients remaining in VF (N=172) after shock delivery. Conclusion: Post-shock rhythms are very volatile in the first minute after shock delivery. Given the large percentage of post-shock rhythm changes, chest compressions should resume for at least 60 seconds immediately after a shock before rhythm and pulse are checked. Technology displaying cardiac rhythm during chest compressions could help to decide whether chest compressions should be stopped for a pulse check at that time.