Clinical Pearls & Morning Reports
Published November 23, 2022
Cheskes et al. conducted a trial that evaluated double sequential external defibrillation (DSED) and vector-change (VC) defibrillation as compared with standard defibrillation in patients who remained in refractory ventricular fibrillation during out-of-hospital cardiac arrest. Read the NEJM Original Article here.
Q: What percentage of patients remain in refractory ventricular fibrillation despite multiple defibrillation attempts during out-of-hospital cardiac arrest?
A: Out-of-hospital cardiac arrest accounts for more than 350,000 unexpected deaths each year in North America. Patients presenting with ventricular fibrillation or pulseless ventricular tachycardia have a higher survival rate than patients with other rhythms. However, despite advances in defibrillator technology, almost half these patients may remain in refractory ventricular fibrillation despite multiple defibrillation attempts.
Q: Where are defibrillation pads placed with use of DSED and VC defibrillation?
A: DSED, the technique of providing rapid sequential shocks from two defibrillators with defibrillation pads placed in two different planes (anterior–lateral and anterior–posterior), has been studied for decades in the electrophysiology laboratory for use in patients with refractory atrial or ventricular fibrillation. VC defibrillation, the technique of switching defibrillation pads from the anterior–lateral to the anterior–posterior position, offers the theoretical potential to defibrillate a portion of the ventricle that may not be completely defibrillated by pads in the standard anterior–lateral position.
A: The primary outcome was survival to hospital discharge. A total of 38 patients (30.4%) in the DSED group survived to hospital discharge, as compared with 18 patients (13.3%) in the standard group (relative risk, 2.21; 95% confidence interval [CI], 1.33 to 3.67); the corresponding number in the VC group was 31 patients (21.7%) (relative risk [vs. standard], 1.71; 95% CI, 1.01 to 2.88). In the generalized linear model, the overall test for differences in survival to hospital discharge according to the randomized treatment assignment was significant (P=0.009 for the comparison among the three groups). Termination of ventricular fibrillation occurred in 105 patients (84.0%) in the DSED group, as compared with 92 patients (67.6%) in the standard group (relative risk, 1.25; 95% CI, 1.09 to 1.44), and return of spontaneous circulation occurred in 58 patients (46.4%) in the DSED group, as compared with 36 (26.5%) in the standard group (relative risk, 1.72; 95% CI, 1.22 to 2.42). Survival with a good neurologic outcome occurred in 34 patients (27.4%) who received DSED and in 15 patients (11.2%) who received standard defibrillation (relative risk, 2.21; 95% CI, 1.26 to 3.88). Among the patients who received VC defibrillation, termination of ventricular fibrillation occurred in 115 (79.9%; relative risk [vs. standard], 1.18; 95% CI, 1.03 to 1.36). The return of spontaneous circulation occurred in 51 patients in the VC group (35.4%; relative risk [vs. standard], 1.39; 95% CI, 0.97 to 1.99), and survival with a good neurologic outcome occurred in 23 (16.2%; relative risk [vs. standard], 1.48; 95% CI, 0.81 to 2.71).
A: The trial did not achieve the planned sample size, since it was stopped early by the data and safety monitoring board as a result of Covid-19–related operational challenges. It is possible that the treatment effect was overestimated, given the small number of events for the primary outcome. The majority of patients were enrolled in an urban setting, where a second defibrillator is more often available, so the findings may not be generalizable to more remote settings. This trial was completed in the prehospital environment, and information regarding patient race and ethnic group, coexisting conditions, outpatient medication use, or in-hospital treatments was not available. Therefore, it is plausible that there could have been confounding factors that influenced patient outcomes.