A Novel Method for Assessing Left Bundle Branch Capture Using the Bidirectional Conduction Time Difference Between...

Left bundle branch area pacing (LBBAP) is an established conduction system pacing strategy; however, confirming left bundle branch (LBB) capture remains challenging.

We propose a novel method for LBB capture confirmation based on the bidirectional conduction time difference between the LBBAP and coronary sinus (CS) leads.

This observational study included 60 patients undergoing de novo left bundle branch-optimized cardiac resynchronization therapy. LBB capture was defined by (1) paced QRS transition, (2) LBB potential with current of injury, or (3) ΔV6 R-wave peak time ≥10 ms. LBBAP-to-CS and CS-to-LBBAP conduction times were measured. ΔLBB-CS ([CS-to-LBBAP] - [LBBAP-to-CS]) was compared between nonselective LBB pacing (NS-LBBP) and left ventricular septal pacing (LVSP).

Among 60 patients (74.7±10.4 years; 42 men), 25 had left bundle branch block and 17 had non-specific intraventricular conduction delay. LBB capture was confirmed in 45 patients (75.0%). LBBAP-to-CS was 114.3±28.0 ms during NS-LBBP (n=43) and 134.2±19.0 ms during LVSP (n=29), whereas CS-to-LBBAP was 143.4±28.5 ms (n=60). ΔLBB-CS was greater during NS-LBBP than LVSP (27.5±9.9 vs. 7.9±7.4 ms, P<0.01). Receiver operating characteristic curve analysis identified a 21.5 ms cutoff for LBB capture (74.4% sensitivity; 100% specificity; area under curve [AUC] 0.95). In patients with baseline LBBB (n=25), a 20.5 ms cutoff for LBB capture yielded 92.9% sensitivity, 100% specificity, and an AUC of 0.99.

ΔLBB-CS ≥ 21.5ms may serve as a novel adjunctive marker of LBB capture during LOT-CRT, with greater diagnostic accuracy at a 20.5 ms cutoff in patients with baseline LBBB.