Lack of impact of baseline QRS morphology on the right heart during long-term left bundle branch pacing in patients with atrioventricular block

ABSTRACT: Background Insights into right ventricle (RV) activation during left bundle branch pacing (LBBP) have postulated direct transseptal and retrograde physiological pathways, which may be absent in patients with infranodal conduction abnormalities. Objective This study compared the long-term impact of LBBP on the right heart in patients with atrioventricular block (AVB) according to the baseline QRS morphology. Methods Eighty-two patients with successful LBBP for AVB were prospectively evaluated for changes in right atrial volume (RAV), RV diameter, tricuspid annulus peak systolic elevation (TAPSE), RV S` wave, and tricuspid regurgitation (TR). Results 41.5% had a baseline narrow QRS, 29.3% had right bundle branch block (RBBB), and 29.3% had left bundle branch block (LBBB). RV activation time was similar between the three groups. The patients were followed over a mean period of 715.7±194.8 days. In the narrow QRS group, there were no changes between the follow-up and the baseline values for RA volumes, RV diameter, RVS`W, and TR, with a significant improvement in the TAPSE. In the LBBB group, there were no differences in RA volumes, RV diameter, RVS`W, and TAPSE at follow-up, but TR worsened from 0.7±0.7 to 1±0.9 (p=0.04). Same changes were seen in the RBBB group, with an increase in TR from 0.6±0.5 to 1±0.7 (p=0.02). There was no inter-group difference in the magnitude of change for each right heart echocardiographic parameter. Conclusion LBBP showed a similar long-term protective effect on the right heart chambers` dimensions and function in patients with AVB, regardless of the baseline QRS morphology.