Is Vagal Response During Left Atrial Ganglionated Plexi Stimulation a Normal Phenomenon?

Abstract

Background: Ganglionated plexi (GPs) play an important role in both the initiation and maintenance of atrial fibrillation (AF). GPs can be located by using continuous high-frequency stimulation (HFS) to elicit a vagal response, but whether the vagal response phenomenon is common to patients without AF is unknown. Methods: HFS of the left atrial GPs was performed in 42 patients (aged 58.0±10.2 years) undergoing ablation for AF and 21 patients (aged 53.2±12.8 years) undergoing ablation for a left-sided accessory pathway. The HFS (20 Hz, 25 mA, 10-ms pulse duration) was applied for 5 seconds at 3 sites within the presumed anatomic area of each of the 5 major left atrial GPs (for a total of 15 sites per patient). We defined vagal response to HFS as prolongation of the R-R interval by >50% in comparison to the mean pre-HFS R-R interval averaged over 10 beats and active-GP areas as areas in which a vagal response was elicited. Results: Overall, more active-GP areas were found in the AF group patients than in the non-AF group patients, and at all 5 major GPs, the maximum R-R interval during HFS was significantly prolonged in the AF patients. After multivariate adjustment, association was established between the total number of vagal response sites and the presence of AF. Conclusions: The significant increase in vagal responses elicited in patients with AF compared with responses in non-AF patients suggests that vagal responses to HFS reflect abnormally increased GP activity specific to AF substrates.