Effects of autonomic interventions on atrial restitution properties

Atrial Restitution Properties.

Introduction: The restitution hypothesis suggests that action potential duration (APD) restitution slope >1 predicts the development of alternans and fibrillation. This study aimed to investigate the effects of autonomic interventions on the restitution properties on the atria.

Methods and results: In 10 anesthetized open-chest dogs, multiple electrode catheters were sutured at pulmonary vein and atrial sites. The monophasic APD was recorded by an Ag-AgCl catheter. The restitution curve at each site was constructed by plotting each APD(90) against the preceding diastolic interval at incremental atrial pacing rates before and after vagal nerve stimulation (VNS) or ganglionated plexi (GP) ablation. Before GP ablation, VNS significantly shortened the APD, flattened the restitution curves and suppressed the APD alternans at each site, while increasing the atrial fibrillation (AF) inducibility and duration (P < 0.05 for all). These effects were eliminated by GP ablation. Compared with the baseline, GP ablation significantly increased the APD, steepened the restitution curves, and facilitated the APD alternans at each site while decreasing the AF inducibility and duration (P < 0.05 for all). VNS significantly increased (0.5 ± 0.2 vs 0.3 ± 0.1, P < 0.05) and GP ablation decreased (0.2 ± 0.1 vs 0.3 ± 0.1, P < 0.05) the spatial dispersion of the slopes of APDR curves, respectively.

Conclusions: The maximal slope of APDR curve alone does not fully account for the changes of AF inducibility and duration induced by autonomic interventions; instead, the spatial dispersion of the APDR kinetics may be an important determinant for susceptibility of AF.