Characteristics and proposed mechanisms of QRS morphology observed during the left bundle branch pacing procedure

Abstract

Background:In performing left bundle branch pacing (LBBP), various QRS morphologies are observed as the lead penetrates the ventricular septum (VS). This study aimed to evaluate these characteristics and infer the mechanism underlying each QRS morphology. Methods:In 19 patients who met the strict criteria for LBB capture, we classified the QRS morphologies observed during the LBBP procedure into seven patterns, the first five of which were determined by the depth of penetration: right ventricular septal pacing (RVSP), intraventricular septal pacing (IVSP1 and IVSP2), endocardial side of left ventricular septal pacing (LVSeP), nonselective LBBP (NS-LBBP), selective LBBP (S-LBBP), and NS-LBBP with anodal capture. The parameters of the QRS morphologies in these seven patterns were evaluated.Results: Among the first five patterns, stimulus-QRSend duration (s-QRSend) was the narrowest in IVSP1 rather than in NS-LBBP, and stimulus-to-peak of R wave in V6 (s-LVAT) was significantly shortened in two steps, from RVSP to IVSP1 (96 ± 11; 82 ± 8 ms, p < .01) and from LVSeP to NS-LBBP (76 ± 7; 60 ± 4 ms, p < .01). The late-R duration in V1 was significantly prolonged in the order of LVSeP, NS-LBBP, and S-LBBP (45 ± 7; 53 ± 10; 71 ± 15 ms, respectively, p < .01).Conclusions: s-QRSend was the narrowest in IVSP1 rather than in NS-LBBP among the QRS morphologies observed during lead penetration through the VS. The prolonged late-R duration in V1 and abrupt shortening of the s-LVAT in V6 may help determine LBB capture during lead penetration. K E Y W O R D Sconduction system pacing, left bundle branch pacing, left ventricular septal pacing, paced QRS duration, paced QRS morphology, pacing-induced cardiomyopathy BACKGROUNDIn 10%−20% of patients with a high right ventricular pacing burden, left ventricular contractility decreases significantly, resulting in pacinginduced cardiomyopathy. 1,2 Recently, the effectiveness of His bundle pacing (HBP) as a type of His-Purkinje conduction system pacing has been reported. 3,4 While HBP is an effective physiological form of pac-ing, it may be limited by challenges during implantation, high thresholds, and low sensing in some patients. [5][6][7] Huang et al. 8 first described left bundle branch pacing (LBBP) as a novel pacing approach in a patient with heart failure and complete LBBB. Recently, the safety and feasibility of LBBP have been reported 9-14 along with its usefulness for CRT-adapted cases. 15,16 LBBP has gained attention as an alternative for HBP. LBBP is a pacing method that captures the left bundle branch

Which Is More Likely to Achieve Cardiac Synchronization: Left Bundle Branch Pacing or Left Ventricular Septal Pacing?

“…LVSP, on the other hand, captures left ventricular septal myocardium, resulting in direct left-to-right septal activation, preserving interventricular dyssynchrony. The terminal R′/r′ wave duration in lead V1, which indicates delayed right ventricular excitation, was significantly longer in LBBP than in LVSP ( 17 ), also indicating that LBBP caused more pronounced interventricular dyssynchrony than LVSP. However, this interventricular synchrony of LVSP may not be physiological.…”

“…It is essentially LBBP with bipolar pacing configuration ( Figure 1C ), with the cathode tip capturing LBB and the anode ring capturing RBB area. Shimeno et al also revealed that the terminal R′/r′ wave duration of LBBP with bipolar pacing configuration is shorter than that of LVSP, presumably due to the contribution of the anodal capture during bipolar pacing ( 17 ). In addition, some previous studies and case reports have shown that LBBP can shorten the QRS duration of intrinsic RBBB or even completely correct RBBB ( 19 – 23 ), while LVSP cannot, but the underlying mechanism remains unclear and needs further study.…”

The Physiologic Mechanisms of Paced QRS Narrowing During Left Bundle Branch Pacing in Right Bundle Branch Block Patients

“…Shimeno et al ( 18 ) observed that the mean threshold of anodal capture in NSLBBP was 4.9 ± 1.2V @ 0.4ms, and that the paced QRS duration was significantly shorter than that without anodal capture (121 ± 9 ms vs. 135 ± 8 ms). Similarly, the average threshold for simultaneous capture of LBB and RBB in cathode tip and anode ring bipolar pacing mode in Lin et al ’s study was 2.7 V @ 0.5 ms ( 26 ).…”

“…When the lead is advancing from the right ventricular septum to the left, the morphology of paced QRS complex changes dynamically, as seen by the W-shaped notch at the nadir of the QRS complex in lead V1 gradually moving to the end of that and eventually presenting a pseudo-RBBB pattern (13,14). This is because LBBP can directly capture the LBB, causing the excitation of the left ventricular lateral wall to be to accelerated while the excitation of the right ventricle (RV) to be delayed (17)(18)(19)(20). LBBP can be divided into two types: selective LBBP (SLBBP), which involves only LBB capture, and nonselective LBBP (NSLBBP), which involves LBB and surrounding myocardium capture.…”

Clinical impact of left bundle branch area pacing in heart failure with preserved ejection fraction and mid‐range ejection fraction

“…21,22 LBBP was defined as LBB capture, which was confirmed when all of the following criteria were satisfied: can be classified into seven patterns based on the lead depth or pacing output. 23 Deep septal pacing (DSP) is the pacing modality in which there is a Qr pattern just after the appearance of the late-R wave in the V1 lead for the first time during lead penetration; Shimeno et al…”