The influence of subclavian ansae stimulation on cardiac hemodynamics and electrophysiology in atrial fibrillation- exploring a novel target for neuromodulation in atrial fibrillation (SAS-AF study)
Authors: Kanthasamy V , Ang R , Sridhar A , Vyas S , Schilling R , Honarbakhsh S , Ahluwalia N , Hunter R , Finlay M 
Published: May 2024

Abstract

Background
Sympathetic nervous system activation plays a significant role in arrhythmia development and maintenance.Neuromodulation techniques such as stellate ganglion block and sympathectomy, are limited by off-target side effects and complex targeting.The Subclavian Ansae (SA,a nerve cord encircling the subclavian artery) may be an intravascular site allowing specific targeting of the cardiac afferent sympathetic system.Preclinical studies have revealed increased sympathetic tone upon selective SA stimulation.

Objective
We sought to define for the first time in Humans the functional anatomy and physiology of Subclavian Ansae via a percutaneous approach.

Methods
A prior cadaveric study defined the anatomical course of the subclavian ansae, encircling the subclavian arteries and connecting the middle cervical ganglia to inferior cervical ganglia/stellate.Patients undergoing catheter ablation for paroxysmal atrial fibrillation(pAF) under general anesthesia were prospectively recruited for the study. Subclavian Ansae stimulation (SAS) was performed on the left and/or the right (L/SAS ± R/SAS) within the subclavian artery using the TactiCath Ablation Catheter introduced via a femoral arterial sheath. Stimulation parameters included up to 70 V output, 10 Hz frequency, and pulse width of 2-4ms for 20-30s. Test pulses ensured no cardiac capture during stimulation. Participants discontinued antiarrhythmic agents at least 4-5 half-lives prior to the procedure. Invasive arterial blood pressure(BP), heart rate (HR), and electrophysiological parameters were recorded in response to selective stimulation. An increase of ten percent or more in either arterial blood pressure(BP) or heart rate(HR) from the initial baseline measurements was deemed a positive response.

Results
15 patients (62±11 years, 9 males, pAF duration 51±24 months) underwent the simulation protocol prior to their clinical AF ablation procedure. A positive hemodynamic response was observed in nine patients, and among them, arrhythmia was inducible in 3 patients (atrial fibrillation in 2 patients and repeated runs of atrial ectopy in 1 patient) in response to SAS. Mean sinus cycle length(CL) decreased(chronotropic) after stimulation,particularly with a significant change observed in response to R/SAS. Additionally,L/SAS led to a notable increase in mean systolic (SBP) and diastolic(DBP) blood pressure (inotropic). While the mean right atrial effective refractory period (ERP) did not significantly decrease after stimulation, there was a demonstrable difference in interatrial conduction time(dromotropy). Six patients, including the initial 3 subjected to low-energy stimulation (up to 12V), did not exhibit an adrenergic response.

Conclusion
This study represents the first successful application of selective SAS in humans. A heterogeneity in electrophysiological modulation by SAS exists, including laterality.The SA is a potential important target for targeted autonomic neuromodulation therapy