Objective To investigate the electrocardiographic effects of left bundle branch pacing (LBBP) in symptomatic bradycardia patients with intrinsic complete right bundle branch block (RBBB).
Methods All of the patients with symptomatic bradycardia and intrinsic complete RBBB were consecutively enrolled from January 2019 to December 2021, attempting to do LBBP in the Department of Cardiology, Xiamen Cardiovascular Hospital of Xiamen University. In the standard 12-lead electro cardiogram, QRS morphology in lead V1, QRS duration, delayed right ventricular activation time (dRVAT), left ventricular activation time (LVAT) and inter-ventricular conduction delay (IVD) were documented and compared between before and after LBBP respectively.
Results A total of 53 patients were included, (72.15±9.39)years old, and 34 of them were male. Forty-six of them underwent LBBP successfully. The QRS morphology was primarily rsR' pattern (83%) before LBBP, whereas the QRS morphology of LBBP was mainly Qr pattern (29/46,63%). When compared to pre-procedure, LBBP significantly reduced the QRS duration [(149.09±12.81) ms vs. (112.46±9.64) ms, P<0.001], fully corrected the QRS duration in 76.08%,(35/463) of cases, partially corrected in 21.73%(10/46), and uncorrected in 2.17%(1/46), and improved IVD [(58.28±12.54) ms vs. (34.34±8.87) ms, P<0.001], but increased LVAT [(42.46±6.95) ms vs. (66.53±10.83) ms, P<0.001]. There was no significant difference in dRVAT [(100.47±12.40) ms vs. (100.86±10.57) ms, P=0.955].
Conclusion LBBP can reduce the QRS duration of intrinsic complete RBBB, improve the interventricular electrical synchronization, and present a Qr-dominated pattern in lead V1.