Right bundle branch pacing: Criteria, characteristics, and outcomes

Abstract

Targets for right-sided conduction system pacing (CSP) include His bundle and right bundle branch. Electrocardiographic patterns, diagnostic criteria, and outcomes of right bundle branch pacing (RBBP) are not known. Our aims were to delineate electrocardiographic and electrophysiological characteristics of RBBP and to compare outcomes between RBBP and His bundle pacing (HBP). Patients with confirmed right CSP were divided according to the conduction system potential to QRS interval at the pacing lead implantation site. Six hypothesized RBBP criteria as well as pacing parameters, echocardiographic outcomes, and all-cause mortality were analyzed. All analyzed criteria discriminated between HBP and RBBP: double QRS transition during the threshold test, selective paced QRS different from conducted QRS, stimulus to selective-QRS > potential-QRS, small increase in V6 R-wave peak time (V6RWPT) during QRS transition, equal capture thresholds of CSP and myocardium, and stimulus-V6RWPT > potential-V6RWPT (adopted as the diagnostic standard). According to the last criterion, RBBP was observed in 19.2% of patients (64 of 326) who had been targeted for HBP, present mainly among patients with potential to QRS <35 ms (90.6% [48 of 53]) and occasionally among the remaining patients (5.6% [16 of 273]). RBBP was characterized by longer QRS (by 10.5 ms), longer V6RWPT (by 11.6 ms), and better sensing (by 2.6 mV) compared with HBP. During a median follow-up duration of 29 months, no differences in capture threshold, echocardiographic outcomes, or mortality were found. RBBP has distinct features that separate it from HBP and is observed in approximately a fifth of patients in whom HBP is intended.