Ultra-high-frequency electrocardiography identifies preserved ventricular synchrony during left bundle branch area pacing compared with right ventricular pacing

BACKGROUND: Right ventricular pacing (RVP) may induce nonphysiological ventricular activation and electrical dyssynchrony, whereas left bundle branch area pacing (LBBAP) is intended to recruit the His-Purkinje system and preserve a more physiological activation pattern. OBJECTIVE: To compare paced-state ventricular activation profiles during LBBAP and RVP using ultra-high-frequency electrocardiography (UHF-ECG). METHODS: In this single-center pilot comparative study, 33 patients undergoing permanent pacing were analyzed (16 LBBAP, 17 RVP). The UHF-ECG comparison was performed exclusively during paced rhythm. Baseline clinical characteristics and paced-state QRS duration, absolute ventricular electrical delay (|VED16|), and mean ventricular delay (MeanVD) were compared between groups. Continuous variables were analyzed with the two-sided Mann-Whitney U test, categorical variables with Fisher's exact test, and effect sizes with Cliff's delta. RESULTS: Age, sex, left ventricular ejection fraction, and NYHA class were broadly comparable between groups, but pacing indication differed. During pacing, LBBAP showed a narrower QRS complex than RVP (108.1 ± 12.9 vs 137.3 ± 18.2 ms; p < 0.0001), lower |VED16| (16.3 ± 12.7 vs 30.0 ± 14.9 ms; p = 0.015), and lower MeanVD (41.8 ± 10.2 vs 54.1 ± 10.9 ms; p = 0.0033). Paced QRS duration ≥120 ms occurred in 6.3% versus 82.4% (p < 0.0001). CONCLUSIONS: Compared with RVP, LBBAP was associated with a more physiological paced ventricular activation pattern characterized by a narrower QRS complex and lower UHF-ECG dyssynchrony metrics.