Feasibility and Outcomes of Upgrading to Left Bundle Branch Pacing in Patients With Pacing-Induced Cardiomyopathy and Infranodal Atrioventricular Block

Abstract

His bundle pacing (HBP) can reverse left ventricular (LV) remodeling in patients with right ventricular (RV) pacing-induced cardimyopathy (PICM) but may be unable to correct infranodal atrioventricular block (AVB). Left bundle branch pacing (LBBP) results in rapid LV activation and may be able to reliably pace beyond the site of AVB. Our study was conducted to assess the feasibility, safety, and outcomes of permanent LBBP in infranodal AVB and PICM patients. Patients with infranodal AVB and PICM who underwent LBBP for cardiac resynchronization therapy (CRT) were included. Clinical evaluation and echocardiographic and electrocardiographic assessments were recorded at baseline and follow-up. Permanent LBBP upgrade was successful in 19 of 20 patients with a median follow-up duration of 12 months. QRS duration (QRSd) increased from 139.3 ± 28.0 ms at baseline to 176.2 ± 21.4 ms (P < 0.001) with right ventricular pacing (RVP) and was shortened to 120.9 ± 15.2 ms after LBBP (P < 0.001). The mean LBBP threshold was 0.7 ± 0.3 V at 0.4 ms at implant and remained stable during follow-up. The left ventricular ejection fraction (LVEF) increased from 36.3% ± 6.5% to 51.9% ± 13.0% (P < 0.001) with left ventricular end-systolic volume (LVESV) reduced from 180.1 ± 43.5 to 136.8 ± 36.7 ml (P < 0.001) during last follow-up. LBBP paced beyond the site of block, which results in a low pacing threshold with a high success rate in infranodal AVB patients. LBBP improved LV function with stable parameters over the 12 months, making it a reasonable alternative to cardiac resynchronization pacing via a coronary sinus lead in infranodal AVB and PICM patients.

Keywords: His bundle pacing (HBP); atrioventricular block (AVB); cardiac pacing; cardiac resynchronization therapy (CRT); heart failure (HF); left bundle branch pacing (LBBP); pacing-induced cardiomyopathy (PICM).

Figure 1

Twelve-lead ECG and intracardiac electrogram (EGM) in a patient. The native cardiac rhythm (A); twelve-lead ECG by right ventricular pacing (RVP) (B); the ECG by left bundle branch pacing (LBBP) (C); narrow ECG QRS with LBB potential in intracardiac electrograms (EGM at the bottom) in a infranodal atrioventricular block (AVB) patient (D). His bundle pacing (HBP) could not pace beyond the block site (2.5 V at 0.4 ms) (E). Selective (0.6 V at 0.4 ms) and non-selective (0.5 V at 0.4 ms) LBBP (F) and the angiogram of the sheath to assess the depth of the LBB LBBP lead (G) are shown. Echocardiography showed the lead was fixed in the left ventricular septum (H), and LBBP but not HBP could pace beyond the block site in one patient of AVB with infranodal block. HBP at 2.5 V/0.4 ms could induce the loss of capture (2:1) (E), while LBBP could induce pacing (1:1) (F), indicating LBBP but not HBP could pace beyond the block site in infranodal AVB patients. His and LBB potential were seen in the pacing location (D).

Figure 2

Paired left ventricular ejection fraction (LVEF) (A) and left ventricular end-systolic volume (LVESV) (B) in all pacing-induced cardiomyopathy (PICM) patients at implant and during the median 12-month follow-up. N, the number of patients who had completed the follow-up of 6 and 12 months; M, the number of patients who completed the follow-up of 6 and 12 months. Data were available in 18/19 patients at 6-month follow-up, in 17/19 patients at the 12-month follow-up, and in 19/19 patients at the median 12-month follow-up.

Figure 3

Dynamic echocardiographic changes in PICM patients with baseline LVEF <40%. Improvement of LVEF (A) and LVESV (B) in PICM patients with LVEF < 40% (6 months). Improvement of LVEF (C) and LVESV in PICM patients with LVEF < 40% (12 months) (D). Data were available in 13/14 patients at the 6-month follow-up and in 12/12 patients at the last follow-up.