Cardiac resynchronization therapy (CRT) with biventricular fusion pacing was found to improve electrical synchrony and left ventricular ejection fraction (LVEF) in patients with right bundle branch block (RBBB), according to a study published in the Journal of Electrocardiology.

Consecutive patients with RBBB who were implanted with a CRT device allowing for biventricular fusion pacing using SyncAV programming were assessed. The patients were compared with a historical cohort of patients with RBBB who had received CRT. QRS complex duration (QRSd) was measured and compared under several conditions: during intrinsic conduction, nominal CRT pacing, and manual electrocardiogram (ECG)-based optimized SyncAV programming. LVEF was compared before CRT and 6 months after CRT.

The analysis included 8 consecutive patients with RBBB (group 1; mean age, 70±12 years; 88% men; 63% with ischemic cardiomyopathy; 75% with CRT-defibrillator; mean New York Heart Association [NYHA] score, 2.1±0.6) who underwent SyncAV programming, and 16 patients with RBBB (group 2; mean age, 71±16 years; 88% men; 63% with ischemic cardiomyopathy; mean NYHA score, 2.3±0.8) from the historical cohort. The mean intrinsic conduction QRSd in groups 1 and 2 were 155±13 ms and164 ± 22 ms, respectively.

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The mean nominally paced QRSd in group 1 was 156±15 ms (ΔQRSd, 1.3±11.6; P =.77) compared with a mean intrinsic conduction QRSd of 155±13 ms, and SyncAV-optimized paced QRSd was 135±14 ms (intrinsic conduction ΔQRSd, −20.0±20.4; P =.03; nominal pacing ΔQRSd −21.3±16.3; P =.008). Mean QRSd with nominal pacing in group 2 was 160±24 ms (ΔQRSd, 3.8±33.4; P =.66 compared with intrinsic conduction).

Baseline LVEF in group 1 was 22.1±11.5, and 27.8±8.6 at the 6-month follow-up (P =.047). Baseline LVEF was 27.2±10.6 in group 2, and 25.0±10.0 at the 6-month follow-up (P =.45).

“Fusion pacing using the SyncAV algorithm was associated with a significant reduction in QRSd compared [with] intrinsic and nominal biventricular pacing in patients with RBBB,” noted the study authors. “Furthermore, fusion pacing using the SyncAV algorithm was associated with a significant improvement in LVEF. Importantly, these findings of a reduction in QRSd and increase in LVEF are in contrast to a similar cohort of patients who did not receive SyncAV fusion pacing.”

Study limitations include its single-center and retrospective design, and small sample.

“Biventricular fusion pacing is associated with improved electrical synchrony and increased LVEF when compared with traditional biventricular pacing in patients with underling RBBB,” the investigators concluded. “This study demonstrated that a simple, ECG-based algorithm to optimize atrioventricular delays can significantly improve electrical synchrony in patients with RBBB.”

Disclosures: One of the authors reported affiliations with pharmaceutical and medical device companies. Please see the original reference for a full list of disclosures.


AlTurki A, Lima PY, Vidal A, et al. Fusion pacing in patients with right bundle branch block who undergo cardiac resynchronization therapy. J Electrocardiol. 2020;64:66-71.