Background: Left bundle branch pacing (LBBP) is a novel technique to achieve physiologic pacing. Criteria for LBB capture has not been fully evaluated.
Objective: To evaluate the electrocardiogramand electrogram characteristics of LV septal pacing with and without LBB capture.
Methods: LV septum was mapped in pacemaker or CRT pts using a multielectrode catheter to record left conduction system potentials(LCS) during LBBP. During pacing from the LBBP lead at 2V/0.4msand 5V/0.4ms, stimulus(S)-retrograde His(H_R), S-LCS, S-QRS_end,S-left ventricular activation time(LVAT), presence of R’ in V1 and S in V6 were documented when the lead was at mid-septum (LVSP) and final position at LV endocardium. LBB capture was confirmed by S-H_R<35ms (non-LBBB) or S-LCS<25ms(LBBB)and correlated with ECG parameters.
Results: 30 patients (non-LBBB 21,LBBB 9), underwent successful LBBP with confirmed LBB capture. Compared to LVSP at 2V/0.4ms, during pacing at 5V/0.4ms (initial LBB capture) and LBBP (SLBBP and NSLBBP) at final depth, S-LVAT and S-QRS_end shortened significantly (90.8±15.2ms VS 70.7±7.7ms VS71.1±9.5mVS 70.1±9.4ms, P<0.001;141.7±16.6 VS 134.3±14.9VS 148.4±24.8m VS 135.0±17.8 ms, P=0.003). Compared to LVSP, LBB capture showed higher incidence of R’ in V1 (23.8% VS. 100.0%, P<0.001) and S in V6 (19.0% VS. 100.0%, P<0.001).Similar results were noted in patients with LBBB.
Conclusion: LBB capture during LBBP was confirmed by recording H_R orLCS potentialswithS-H_R<35ms (non-LBBB) or S-LCS<25ms(LBBB). Paced QRS as a RBBB patternwith abrupt shortening of S-LVAT could be used as a simple practical criterion to confirm LBB capture in clinical practice.