Abstract 28: A Paradoxical Increase in VF Prevalence Over the Period Immediately After Sudden Cardiac Arrest
Introduction: Ventricular fibrillation and/or tachycardia (VF/VT) is an important cause of sudden cardiac arrest. When left untreated, as the period with no myocardial blood flow progresses, the initial VF/VTs degrade into asystole with the VF/VT prevalence decreasing over the period from collapse to initial ECG documentation (down time). Using the national registry of out-of-hospital cardiac arrest, we have examined how the VF/VT prevalence changed with the down time.
Methods and Results: Initial ECG rhythms of 173,767 out-of-hospital witnessed cardiac arrest patients were obtained. Bystander CPR was provided in 60,280 patients and those patients were excluded from the analysis. The down time was defined as the time from witnessed collapse to the time of initial ECG documentation by the EMT. Down time was 0 (zero) when cardiac arrest was witnessed by the attending EMTs in patients under ECG monitoring. At time zero, the prevalence of VF/VT, PEA and asystole were 12.2% (311/ 2,511), 43.0% (1,097/ 2,551) and 44.8% (1,143/ 2,551), respectively (Fig). The VF/VT prevalence gradually increased with the down time to reach a maximal value of 23.2% at 7 minutes and almost exponentially decreased thereafter. The prevalence of asystole decreased initially and then increased. The prevalence of PEA decreased almost linearly.
Conclusions: The reasons for the initial and unexpected increase in the VF/VT prevalence remain only to be speculated. Documentation of time of collapse relied mostly on the bystander interview. Although thus contaminated time data may have created a deceptive initial increase of the VF/VT prevalence, it does not completely explain the initial increase in the VF/VT prevalence. The initial decrease of the prevalence of asystole suggests that asystole may converts spontaneously into VF/VT. Initially documented VF/VTs appear to consist of “true” VF/VTs that start as VF/VT as well as those VF/VTs that originate from PEA and/or asystole.
- © 2011 by American Heart Association, Inc.