Left bundle branch pacing compared to left ventricular septal myocardial pacing increases interventricular dyssynchrony but accelerates left ventricular lateral wall depolarization

Abstract

The left bundle branch pacing compared to left ventricular septal myocardial pacing increases interventricular dyssynchrony but accelerates left ventricular lateral wall depolarization,

Left Ventricular Myocardial Septal Pacing in Close Proximity to LBB Does Not Prolong the Duration of the Left Ventricular Lateral Wall Depolarization Compared to LBB Pacing

“…LVSP was observed to be 98% of the distance between the right septum and nsLBBp pacing positions (14.8 mm vs. 15.1 mm), and LBBpotential was observed in a majority of cases (82%). LVSP caused the same interventricular dyssynchrony as left septal myocardial captures with terminal r/R morphology studied previously ( 4 ) (on average −16 ms). However, the LV lateral wall depolarization durations using LVSP in close proximity to LBB were shorter and similar to those seen during both sLBBp and nsLBBp.…”

“…As we showed in our previous work on a similar group of patients with bradycardia using the same methodology for lead depth measurement, terminal rs/Rs morphology in V1 during left septal myocardial pacing appeared ~2/3 (10 mm, i.e., 67%) of the distance between the right septum and pacing positions with nsLBBp. Terminal r/R morphology in V1 during left septal myocardial pacing was present on average 4/5 (12 mm, i.e., 81%) of the distance between the right septum and nsLBBp pacing positions ( 4 ). These two capture types resulted in less interventricular dyssynchrony but prolonged LV lateral wall depolarization duration compared to nsLBBp.…”

“…However, this paced QRS pattern is also present in left septal positions that are shallower than positions where LBB capture could be observed during pacing maneuvers ( 2 , 3 ). Our previous study used the ultra-high-frequency ECG (UHF-ECG) to show that myocardial capture of the left septum (in positions where nsLBBp was not obtainable with pacing outputs up to 5 V at 0.5 ms) produced less interventricular dyssynchrony but prolonged LV lateral wall depolarization durations compared to nsLBBp ( 4 ). The impact of pure myocardial left septal pacing using pacing positions, which are closer to the LBB, i.e., locations where left septal myocardial capture appears from nsLBBp while decreasing pacing outputs, is not known.…”

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

“…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.…”

Left Bundle Branch Pacing: A Perfect Compromise?

“…LVSP activates both ventricles with delay, resulting in relative interventricular synchrony; it does not provide intraventricular synchrony, however. [ 28 ]…”