Acute echocardiographic and hemodynamic response to his‐bundle pacing in patients with first‐degree atrioventricular block

BACKGROUND: Atrial pacing and right ventricular (RV) pacing are both associated with adverse outcomes among patients with first‐degree atrioventricular block (1°AVB). His‐bundle pacing (HBP) provides physiological activation of the ventricle and may be able to improve both atrioventricular (AV) and inter‐ventricular synchrony in 1°AVB patients. This study evaluates the acute echocardiographic and hemodynamic effects of atrial, atrial‐His‐bundle sequential (AH), and atrial‐ventricular (AV) sequential pacing in 1°AVB patients. METHODS: Patients with 1°AVB undergoing atrial fibrillation ablation were included. Following left atrial (LA) catheterization, patients underwent atrial, AH‐ and AV‐sequential pacing. LA/left ventricular (LV) pressure and echocardiographic measurements during the pacing protocols were compared. RESULTS: Thirteen patients with 1°AVB (mean PR 221 ± 26 ms) were included. The PR interval was prolonged with atrial pacing compared to baseline (275 ± 73 ms, p = .005). LV ejection fraction (LVEF) was highest during atrial pacing (62 ± 11%), intermediate with AH‐sequential pacing (59 ± 7%), and lowest with AV‐sequential pacing (57 ± 12%) though these differences were not statistically significant. No significant differences were found in LA or LV mean pressures or LV dP/dT. LA and LV volumes, isovolumetric times, electromechanical delays, and global longitudinal strains were similar across pacing protocols. CONCLUSION: Despite pronounced PR prolongation, the acute effects of atrial pacing were not significantly different than AH‐ or AV‐sequential pacing. Normalizing atrioventricular and/or inter‐ventricular dyssynchrony did not result in acute improvements in cardiac output or loading conditions.