Cardiac resynchronization therapy in non-ischemic cardiomyopathy: a comparative non-randomized study of His bundle pacing versus biventricular pacing
Authors: Moraleda Salas M , Rodriguez-Albarran A , Arce-Leon A , Esteve-Ruiz I , Venegas-Gamero J , Fernandez-Gomez J , Morina-Vazquez P 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Cardiac resynchronization therapy (CRT) via permanent His bundle pacing (pHBP) has gained acceptance globally, but robust studies comparing pHBP-CRT with classic CRT are lacking.

Purpose
To compare the improvement in left ventricular ejection fraction (LVEF) after pHBP-CRT vs classic CRT.

Methods
Single-center study comparing a prospective series of pHBP-CRT with a historical series of CRT via classic biventricular pacing (BVP). Patients with non-ischemic cardiomyopathy, baseline LVEF &lt;35%, left bundle branch block (LBBB), and CRT indications were selected.

Results
Fifty-one patients underwent classic CRT and 52 patients underwent pHBP-CRT (26.9% selective vs 73.1% non-selective HBP with LBBB correction). In 2 patients, pHBP was not possible: one of them cause of high thresholds and the other because QRS correction was lacking. The baseline characteristics are shown in Table 1. In the classic CRT group, 74.5% of patients were in sinus rhythm (SR) and 25.5% in atrial fibrillation (AF). In the pHBP group, 88.5% were in SR and 11.5% in AF (p=0.07). The median VP was 98.5% (94.3–100%) in the former group and 99% (98–100%) in the latter (p=0.484). Regarding LVEF, the primary objective of this study, in the classic CRT group, the median basal LVEF was 30% (29–35%) before implantation and 40% (35–48%) at follow-up. In the pHBP-CRT group, the median basal LVEF was 30% (28–34%) before implantation and 55% (45–60%) at follow-up (p=0.001). In the classic CRT group, the absolute increase in LVEF was &gt;20%, 10–20%, and 5–10% in 19.6%, 31.4%, and 15.7% of patients, respectively. In the pHBP-CRT group, the absolute increase in LVEF was &gt;20%, 10–20%, and 5–10% in 55.8%, 32.7%, and 7.7% of patients, respectively, (p=0.001). The characteristics of the basal and paced QRS, as well as the His thresholds, are shown in Table 2. Considering the secondary objective of our study, the median long-term (after a year) His recruitment threshold with LBBB correction was 1.25 (1–2.5) V at 0.4 ms in cases where pHBP-CRT was performed, compared to an LV coronary sinus threshold of 1.25 (1–1.75) V at 0.4 ms in cases where classic CRT was performed; there was no significant difference between the two groups (p=0.48). The basal QRS duration was similar in both groups; after CRT, the median paced QRS duration was 135 (120–145) ms for pHBP-CRT and 140 (130–150) ms for BVP-CRT (p=0.586). Considering the concept of effective QRS in patients who underwent pHBP CRT, the median paced QRS was 110 (110–120) ms (p=0.001) compared to the classic CRT.

Conclusions
The improvement in LVEF was superior in patients who underwent pHBP-CRT than in those that received classic CRT. The threshold levels after 1 year of follow-up period were similar for LBBB correction with pHBP or conventional BVP. Randomized prospective studies with larger populations and longer follow-up periods are needed to verify our results.