Procedural characteristics
All patients included in this study underwent clinically successful implants. HBP took significantly longer and required significantly more fluoroscopy compared to LBBAP (124.7±50.4 vs. 105±28.8 minutes, p = 0.023; 19.8±15.9 vs. 13.7±7.4 minutes; p = 0.019). These differences persisted even after excluding cases (4 HBP cases and 1 LBBAP case) in which physiologic pacing was used as a bailout option after inadequate resynchronization therapy with a coronary sinus lead (118.7±48.0 vs. 103.7±27.8 minutes, p = 0.037; 16.8±12.2 vs. 13.1±6.2 minutes; p = 0.036).
The post-implant paced QRS width in the HBP and LBBAP groups were similarly narrow (119.8±21.2 vs.116.7±15.2 ms, p = 0.443) with a 19.8% and 17.2% reduction of QRS width from baseline, respectively. Stimulus to peak R wave in lead V6 (RWPT) times were not significantly different in patients undergoing HBP and LBBAP (80±22.9 vs. 76.4±14.5 ms, p = 0.370). Post-procedurally, 86.7% of the LBBAP group achieved APE, while only 68.8% of the HBP group met the APE (Figure 1 ). This difference was not statistically significant. When analyzed independently, however, the pacing threshold was significantly higher in patients undergoing HBP (1.1±0.9 vs. 0.5±0.3 V, p < 0.001) and R-wave amplitude and impedance were significantly lower in patients undergoing HBP compared to LBBAP (8.7±6.1 vs. 11.9± 5.7 mV, p = 0.035; 615.3±209.8 vs. 715±154.2 Ohms, p = 0.012) (Figures 2 ). There were no immediate procedure-related complications noted in either group