Abstract / Summary
Background Left bundle branch area pacing may reduce new‐onset atrial fibrillation. However, its mechanism and the comparison of atrial reverse remodeling effect between left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP) has not been elucidated. We aim to investigate reverse atrial remodeling by LBBP and LVSP in a canine model of rapid pacing‐induced dyssynchronous heart failure (DHF). Methods Twenty‐six beagles followed a 6‐week protocol: controls (n=4), rapid atrial pacing (n=4), DHF (n=6), DHF+LBBP and DHF+LVSP (3 weeks DHF followed by 3 weeks LBBP or LVSP, both n=6). Atrial emptying fraction, functional, and electrophysiological parameters were dynamically assessed. Atrial fibrosis was analyzed in tissue samples. Results Within 3 weeks DHF increased atrial volumes and diminished RA and LA emptying fraction and strains significantly compared with baseline. Subsequent 3 weeks of LBBP increased emptying fraction and strains significantly. At week 6, P‐wave duration was shorter in DHF+LBBP than in DHF. Atrial fibrillation was only inducible in DHF animals. Left atrial appendage levels of collagen I/III and α‐SMA deposition and fibrosis were lower in DHF+LBBP compared with DHF animals. LBBP reversed atrial structural and electrical parameters to the levels in rapid atrial pacing animals. LVSP improved those parameters compared with those in DHF but did not normalize them to the levels in the rapid atrial pacing animals. Conclusions LBBP significantly reverses DHF‐induced functional, cellular, and molecular remodeling in the atria, while a smaller amelioration is achieved with LVSP. The findings may explain the reduction in new‐onset atrial fibrillation after LBBP.