Ablation of epicardial ganglionated plexi increases atrial vulnerability to arrhythmias in dogs

Abstract

Background: Previous studies have suggested that systematic ablation of ganglionated plexi (GP) could increase the short-term success rate of radiofrequency ablation for atrial fibrillation, but the long-term efficacy of this approach is not fully established.

Methods and results: Twenty-four mongrel dogs were divided into 3 groups: epicardial GP ablation group 1 (n=8), epicardial GP ablation group 2 (n=8), and a sham operation group (n=8). In the 2 epicardial GP ablation groups, the 4 major GP and the ligament of Marshall were systematically ablated. The effective refractory period and inducibility of tachyarrhythmias were measured before and immediately after GP ablation in epicardial GP ablation group 1 and 8 weeks later in the other 2 groups. Tyrosine hydroxylase and choline acetyltransferase expressions were also determined immunohistochemically 8 weeks later in the latter groups. Compared with epicardial GP ablation group 1 and the sham operation group, epicardial GP ablation group 2 had the shortest atrial and ventricular effective refractory period and the highest inducibility of atrial tachyarrhythmias. The inducibility of ventricular tachyarrhythmias among the 3 groups was comparable. The density of tyrosine hydroxylase- and choline acetyltransferase-positive nerves in the atrium was the highest in epicardial GP group 2, whereas there were no significant intergroup differences in the densities of these 2 types of nerves in the ventricle.

Conclusions: After 8 weeks of healing, epicardial GP ablation without additional atrial ablation was potentially proarrhythmic, which may be attributable to decreased atrial effective refractory period and hyper-reinnervation involving both sympathetic and parasympathetic nerves.

Keywords: atrial fibrillation; autonomic nervous system; catheter ablation; denervation; remodeling.