Right Bundle Branch Pacing: Criteria, Characteristics, and Outcomes

Authors, Journal, Affiliations, Type, DOI

• Authors: Marek Jastrzębski (corresponding); Grzegorz Kiełbasa; Paweł Moskal; Agnieszka Bednarek; Marek Rajzer; Karol Curila; Haran Burri; Pugazhendhi Vijayaraman
• Journal: Heart Rhythm 2023;20(4):492–500. © 2023 Heart Rhythm Society
• Affiliations: First Department of Cardiology, Interventional Electrocardiology and Hypertension, Jagiellonian University Medical College, Kraków; Electrophysiology Laboratory, University Hospital in Kraków; Cardiocenter, Charles University and University Hospital Královské Vinohrady, Prague; Cardiac Pacing Unit, University Hospital of Geneva; Geisinger Heart Institute, Wilkes-Barre
• Type: Single-centre retrospective analysis of a prospectively maintained CSP database — 1,412 CSP implants screened, 403 HBP/RBBP, 326 included; median follow-up 29 months
• DOI: 10.1016/j.hrthm.2023.01.017
• Disclosures: Burri — speaker/consulting/fellowship support from Abbott, Biotronik, Boston Scientific, Medtronic, MicroPort; Vijayaraman — honoraria, consulting and research support from Medtronic, Abbott, Biotronik, Boston Scientific, Eagle Point, and a His delivery-tool patent; Jastrzębski — consulting/lecture fees from Medtronic and Abbott

Overview

The right bundle branch is an accessible right-sided pacing target, but it had never been formally described: no criteria, no prevalence, no outcomes. This paper supplies all three. Using the conduction-system potential-to-QRS interval at the implant site, it separates HBP (potential–QRS 35–55 ms) from RBBP (<35 ms), then tests six candidate criteria against that split. The best — stimulus-to-V6RWPT longer than potential-to-V6RWPT by ≥10 ms — reflects the fact that during RBBP the wavefront must travel retrogradely up the RBB, across to the LBB, then anterogradely down it, whereas during HBP the paced and native routes are identical. By this standard, RBBP occurred in 19.6% of patients in whom HBP was intended (64/326) — 90.6% of those with a potential–QRS <35 ms and 5.6% of the rest. RBBP gave longer QRS by 10.5 ms, longer V6RWPT by 11.6 ms, and better sensing by 2.6 mV than HBP, with no difference in capture threshold, echocardiographic outcomes or 3-year mortality. Its clinical niche is narrow but real: RBBP cannot correct LBBB, yet it avoids transseptal access and offers excellent sensing and myocardial backup.

Keywords

Right bundle branch pacing; His bundle pacing; Conduction system pacing; Capture criteria; ECG

Key Takeaways

Population and definitions

• 1,412 CSP implants screened → 403 HBP/RBBP → 326 included (80.9%); 77 excluded mainly for H-V >55 ms or baseline LBBB
• Inclusion: lead in the RV septal/His area; confirmed conduction-system capture by QRS transition; H-V/RB-V <55 ms; baseline QRS other than LBBB
• RBBP defined by the potential-to-QRS interval at the pacing lead, with <35 ms used as the initial discriminator between RBBP and HBP
• RBBP prevalence: 64/326 (19.6%) at any output — RBBP alone 36 (11.0%), both RBBP and HBP 28 (8.6%), HBP alone 262 (80.4%)
• At working output (3.0–3.5 V/0.4 ms), RBBP was present in 40/326 (12.2%) (42/64 of the RBBP patients; 22 had HBP at working output)
• Potential–QRS <35 ms in 53 patients (16.2%); among them RBBP in 48/53 (90.6%), versus 16/273 (5.6%) of the rest
• In the <35 ms group: HBP at any output 5 (9.4%), RBBP at near-threshold 13 (24.5%), RBBP at working output 35 (66.0%)
• Baseline: age 75.1–75.3 years; native QRS 108.6–111.5 ms; narrow QRS 58%, RBBB 8–11%, NIVCD 11–20%

The six candidate criteria

• The first criterion was the initial reference standard, but the third replaced it because it identified an additional 36 RBBP cases without any HBP at high output (i.e., without a double transition); 93.3% of those had potential–QRS <35 ms, and all had at least one other RBBP criterion (median 2)
• The physiological basis of criterion 3: during HBP the route from the HB to the LV lateral wall is the same in pacing and native conduction, so paced and native V6RWPT are equal (the same rule holds for LBBP). During RBBP the wavefront must go RBB → HB → LBB → LV, so the paced interval exceeds the native RB-V-to-V6 interval
• Criterion 4 has a counterintuitive logic: even with preserved RBB conduction, the RB-V interval during RBBP is determined by LBB activation of the septum, because QRS onset depends on the left-sided wavefront; the LBB–RBB conduction-time difference (5–20 ms) sets the upper limit of the latency prolongation

Conduction and ECG characteristics

• Transition ns-HBP → ns-RBBP: V6RWPT +11.6 ± 4.3 ms (86.6 → 98.2), QRS +10.5 ± 5.4 ms (133.2 → 143.7) — both P < .0001
• Selective RBBP was observed only at low/near-threshold output; at working output RBBP was always nonselective because of the ample myocardium around the RBB
• ECG during RBBP: features of LV activation delay — smaller r and deeper S in V1–V3, delayed V6 R-wave peak, global QRS prolongation, and a pronounced pseudo-delta wave; the ns-RBBP QRS is intermediate between HBP and RVSP
• In complete RBBB, s-RBBP and HBP produce identical QRS morphologies, but the latency during selective RBB capture can be exceptionally long

Outcomes — RBBP versus HBP (working-output captures)

• The unambiguous advantage is sensing — roughly 2.4 mV higher acutely and chronically, with no undersensing in the RBBP group
• Thresholds were equivalent, and the numerical absence of late threshold rise and lead revision in the RBBP group did not reach significance
• The mortality difference is not significant, but the cohort is elderly and the follow-up is median 29 months, so the study is underpowered for survival

Where RBBP fits

• Advantages: excellent sensing; obligatory myocardial backup capture at working output; no transseptal access, which may facilitate extraction and is relevant to leadless conduction-system pacing; a para-RBB midseptal position gives faster access to the distal conduction system if RBB capture is lost
• Disadvantages: more delayed LV activation than HBP or LBBP; paced QRS is usually <150 ms — possibly enough to prevent pacing-induced cardiomyopathy, but likely insufficient for optimal CRT response; and RBBP cannot correct LBBB, so it is unsuitable as sole therapy for most CRT candidates
• The proposed niche: dual-branch pacing (RBBP + LBBP) to restore both sides of the conduction system, or RBBP combined with coronary venous pacing when fusion with intrinsic RBB conduction is not feasible (e.g., AF)

Limitations of the document

Authors' own stated limitations

• Single-centre, retrospective, observational design with all its inherent limitations
• Preselection of patients with preserved infranodal conduction
• Lack of information on the percentage of ventricular pacing, which limits interpretation of the mortality and echocardiographic outcomes

Additional limitations evident in the study

• There is no direct proof of RBB capture. The gold standard is an ECG interval difference (ΔV6RWPT ≥10 ms), which is itself a physiological inference validated against a double transition in only 28 patients. The 36 additional "RBBP" cases without a double transition are classified by the criterion being tested — a degree of circularity the paper acknowledges only implicitly
• The six criteria were derived and evaluated in the same cohort. Sensitivity and specificity are in-sample point estimates without confidence intervals, and no external validation is reported
• The population is selected in a way that bounds the conclusion: patients were targeted for HBP, not for RBBP, and 77 were excluded for H-V >55 ms or LBBB. The 19.6% prevalence therefore describes HBP-intended patients with preserved infranodal conduction, not a general CSP population, and says nothing about RBBP in LBBB — the population where it is least likely to help
• The outcome comparison is non-randomised and unadjusted. RBBP and HBP groups differ by lead position and operator selection, and the analysis does not adjust for age, comorbidity, pacing indication, or percentage of ventricular pacing. The numerically lower threshold rise and lead revision in RBBP may reflect selection and shorter effective follow-up rather than a property of the site
• Mortality is reported as a crude proportion (12/42 vs 66/284) rather than a time-to-event analysis; with a median 29-month follow-up and an elderly cohort, censoring and competing risk are not addressed
• The echocardiographic comparison is tiny — delta LVEF/LVEDD available in only 27 RBBP and 126 HBP patients, with wide interquartile ranges crossing zero
• RBBP at working output was always nonselective, so the outcomes describe non-selective RBBP, not the selective state that the criteria are built to identify
• The "double transition" criterion is qualitative and operator-dependent, requiring recognition of multiple morphology changes during a threshold run; no reproducibility data are given
• The potential–QRS <35 ms cut-off is acknowledged to be imperfect, because His bundle length, RBB takeoff and conduction velocity vary; the paper itself reports HBP in 9.4% of the <35 ms group and RBBP in 2.6% of the ≥35 ms group
• No lead extraction data, despite extraction being one of the proposed advantages of avoiding transseptal access
• No clinical heart-failure outcomes, hospitalisation, or quality-of-life data, so the claim that RBBP may prevent pacing-induced cardiomyopathy is inferential from QRS duration
• Rating rationale: rated high. This is the first systematic description of RBBP, with a large screened cohort, a clear electrophysiological mechanism, six tested criteria, and a long follow-up with a direct HBP comparison. It is not very high because it is single-centre and retrospective, the diagnostic standard is an ECG inference without direct capture proof, the criteria are derived and tested in the same patients, the cohort is selected for HBP and excludes LBBB, and the outcome comparison is unadjusted and underpowered

Key Concepts Mentioned

• concepts/Right-Bundle-Branch-Pacing — the modality this paper defines
• concepts/Conduction-System-Pacing — the umbrella category
• concepts/His-Bundle-Pacing — the proximal right-sided target and the comparator
• Potential-to-QRS interval — <35 ms suggests RBBP, 35–55 ms HBP
• Stimulus–V6RWPT > potential–V6RWPT (Δ ≥10 ms) — the diagnostic standard for RBBP
• Double QRS transition — successive transitions across HB, RBB and myocardium during threshold testing
• Selective vs nonselective RBBP — selective only at low output; nonselective at working output
• Paced latency vs native latency — stimulus-to-QRS versus potential-to-QRS; the RBBP latency exceeds the RB-V interval
• Retrograde RBB → HB → LBB conduction — the physiological reason paced V6RWPT is longer than native during RBBP
• Myocardial backup capture — the obligatory local myocardial capture at working output
• Dual-branch pacing — combined RBBP and LBBP, proposed for full biventricular conduction-system restoration

Key Entities Mentioned

• concepts/Right-Bundle-Branch-Pacing — the concept page this source creates
• Jagiellonian University Medical College and University Hospital, Kraków — the investigating centre
• Marek Jastrzębski; Karol Curila; Haran Burri; Pugazhendhi Vijayaraman — the investigators
• Boston Scientific LabSystem PRO — the EP recording system
• Vijayaraman — prior work on simultaneous right and left bundle pacing
• Heart Rhythm Society / Elsevier — publisher

Wiki Pages Updated

• Created: wiki/sources/right-bundle-branch-pacing-hrs-2023.md
• Created: wiki/concepts/Right-Bundle-Branch-Pacing.md
• Updated: wiki/concepts/Conduction-System-Pacing.md
• Updated: wiki/concepts/His-Bundle-Pacing.md
• Updated: wiki/sourceindex.md
• Updated: wiki/wikiindex.md