Electrode Positioning for Direct Current Cardioversion for Atrial Fibrillation

No statistically significant difference in efficacy exists for anteroposterior (AP) vs anterolateral (AL) electrode placement for direct current cardioversion (DCCV) for atrial fibrillation (AF). These findings were published in Heart, Lung and Circulation.

Investigators sought to compare the efficacy of AL vs AP electrode placement for DCCV for AF. Primary endpoints were overall DCCV success and first-shock success. Energy level of first successful shock, cumulative energy level necessary for successful cardioversion, and number of shocks represented secondary endpoints.

The investigators conducted a meta-analysis via search of EMBASE, Medline, and Central Register of Controlled Trials electronic databases from inception to February 2022 for patients receiving DCCV for AF in randomized controlled trials (RCTs). Included studies were written in English and compared AL vs AP electrode positioning in adults. They performed subgroup analysis of defibrillator monophasic vs biphasic waveform.

The investigators included 12 RCTs (N=2046; mean age range, 58-69 years) of whom 1009 were randomly assigned to anteroposterior electrode positioning and 1037 to anterolateral electrode positioning. Begg’s rank correlation test revealed no publication bias for either primary endpoint (DCCV P =.44; first-shock success P =.88). Among the 12 RCTs (all with a majority of men), 5 exclusively enrolled patients with persistent AF. Half of the trials used biphasic defibrillation shocks. A quarter of the trials used hand-held paddles, 8 used self-adhesive pads, and 1 used a combination of both. Various energy levels for the initial shock were employed and escalation protocol differed between RCTs. Definitions of success varied from 1 sinus beat to 60 minutes sustained sinus rhythm.

The investigators found no statistically significant difference in AL vs AP electrode positioning for overall DCCV success (relative risk [RR], 1.01; 95% CI, 0.96-1.05; P =.78) and there was significant heterogeneity (I²=63%; P =.003). Additionally, first-shock success did not significantly differ between groups (RR, 0.92; 95% CI, 0.79-1.07; P =.28) and also had significant heterogeneity (I²=66%; P <.001).

They noted similarities in the AL vs AP groups for cumulative energy delivered (mean difference [MD], 39 joules; 95% CI, -168 to 246), energy level of first successful shock (MD, 3 joules; 95% CI, -20 to 27), and the mean number of shocks (MD, 0.3; 95% CI, -0.4 to 0.9).

The investigators found improvement in overall DCCV success with AL electrode positioning (RR, 0.97; 95% CI, 0.93-1.01; P =.09) and improvement in first-shock success with AL electrode positioning (RR, 0.85; 95% CI, 0.69-1.03; P =.10), neither of which were statistically significant.

They found longer AF duration, higher BMI, and older age were significant moderators which favored AL electrode positioning according to metaregression analyses. Initial shock, left ventricular ejection fraction, proportion on amiodarone, left atrial diameter, prevalence of coronary artery disease, proportion of men, or publication year were not significant moderators.

Study limitations include the variation between studies in approach to antiarrhythmic drug therapy prior to DCCV and the clinical characteristics of participants. Additional limitations include the small number of trials that reported on secondary outcomes and the lack of individual patient data.

 “…pooled analysis of randomized data does not show a significant difference in DCCV success between anteroposterior and anterolateral electrode placement,” the study authors wrote. “Meta-regression and subgroup analyses suggest that, in contemporary practice with the use of biphasic defibrillators, there may be a subset of AF patients (those who are older, more obese, and with longstanding persistent AF) in whom anterolateral electrode positioning improves efficacy of DCCV.”