BACKGROUND: 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. OBJECTIVE: Our aims were to delineate electrocardiographic and electrophysiological characteristics of RBBP and to compare outcomes between RBBP and His bundle pacing (HBP). METHODS: Patients with confirmed right CSP were divided according to the conduction system potential to QRS complex interval at the pacing lead implantation site. Six hypothesized RBBP criteria as well as pacing parameters, echocardiographic outcomes, and all-cause mortality were analyzed. RESULTS: All analyzed criteria discriminated between HBP and RBBP: double QRS complex transition during the threshold test, selective paced QRS complex different from conducted QRS complex, stimulus to selective-QRS complex > potential-QRS complex, small increase in V6 R-wave peak time (V6RWPT) during QRS complex 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 complex interval <35 ms (90.6% [48 of 53]) and occasionally among the remaining patients (5.6% [16 of 273]). RBBP was characterized by longer QRS complex (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. CONCLUSION: RBBP has distinct features that separate it from HBP and is observed in approximately a fifth of patients in whom HBP is intended.

1st Department of Cardiology Interventional Electrocardiology and Hypertension Jagiellonian University Medical College Krakow Poland

1st Department of Cardiology Interventional Electrocardiology and Hypertension Jagiellonian University Medical College Krakow Poland; Electrophysiology Laboratory University Hospital in Krakow Krakow Poland

Cardiac Pacing Unit Cardiology Department University Hospital of Geneva Geneva Switzerland

Cardiocenter Charles University and University Hospital Kralovske Vinohrady Prague Prague Czech Republic

Electrophysiology Laboratory University Hospital in Krakow Krakow Poland

Geisinger Heart Institute Geisinger Commonwealth School of Medicine Wilkes Barre Pennsylvania

References provided by Crossref.org

European Society of Cardiology (ESC) clinical consensus statement on indications for conduction system pacing, with special contribution of the European Heart Rhythm Association of the ESC and endorsed by the Asia Pacific Heart Rhythm Society, the Canadian Heart Rhythm Society, the Heart Rhythm Society, and the Latin American Heart Rhythm Society

EHRA clinical consensus statement on conduction system pacing implantation: endorsed by the Asia Pacific Heart Rhythm Society (APHRS), Canadian Heart Rhythm Society (CHRS), and Latin American Heart Rhythm Society (LAHRS)

EHRA clinical consensus statement on conduction system pacing implantation: executive summary. Endorsed by the Asia-Pacific Heart Rhythm Society (APHRS), Canadian Heart Rhythm Society (CHRS) and Latin-American Heart Rhythm Society (LAHRS)