Methods of infra-operative high frequency stimulation to cardiac intrinsic autonomic ganglionk plexi

Abstract

Objective Epicardial mapping of cardiac intrinsic autonomic ganglions was not standardized. The purpose of the present study is to standardize methods of intra-operative high frequency stimulation (HFS) to the ganglionic plexi and to e valuate the effect of micro-wave epicardial ablation on the plexi. Methods 16 cardiac surgical patients were recruited in the intra-operative HFS study. 12 of them were on sinus rhythm while the other 4 were on AF. HFS was applied to epicardial fat pads on or around the heart by a 2-electrode EP catheter. Atrial EKG and body surface EKG were simultaneously recorded with the HFS signal. After measuring atrial effective refractory period (AERP) , HFS was applied to sinus rhythm patients with the duration of 1/2 and 3/4 AERP. Each HFS episode was coupled by an atrial-pacing signal with 600 ms interval. For AF patients , continuous HFS was applied without coupling to native atrial beats. Vagal response was observed to identify the location of the plexi. Micro-wave ablation was employed for AF patients. After the ablation and cardioversion, synchronized HFS was applied again as we did for patients with sinus rhythm. Results 2 cases were excluded due to complete AV block after anesthesia. Vagal response could be induced in every patient while each patient had different fat pads responding to HFS. PR interval on body surface EKG was increased in the responding fat pads as the duration of HFS increased. 2:1AV conduction block was induced eventually in all sinus patients when HFS duration was increased to 3/4 AERP. For AF patients, average PR interval doubled when the responding fat pads were stimulated by continuous HFS. 13/14 cases (92% ) had vagal response in fat pads around right superior pulmonary vein. The positive vagal response was significantly more prevalent in the fat pads on the right side of the heart than on the left side. No vagal response could be induced again after micro-wave ablation in AF patients. Conclusion Epicardial HFS can effectively locate the gangalionated plexi of intrinsic cardiac autonomic nerve during surgery. Epicardial micro-wave ablation can eliminate the vagal response which had been induced before the ablation. Key words: Heart; Ganglia; Atrial fibrillation; Electric stimulation; Vagal response