Subclavian Ansae Stimulation on Cardiac Hemodynamics and Electrophysiology in Atrial Fibrillation: A Target for Sympathetic Neuromodulation.

Background: The sympathetic autonomic nervous system plays a major role in arrhythmia development and maintenance. Historical preclinical studies describe preferential increases in cardiac sympathetic tone upon selective stimulation of the subclavian ansae (SA), a nerve cord encircling the subclavian artery.

Objectives: This study sought to define, for the first time, the functional anatomy and physiology of the SA in humans using a percutaneous approach.

Methods: The authors prospectively recruited patients undergoing catheter ablation for paroxysmal atrial fibrillation (AF) under general anesthesia. SA stimulation (SAS) was performed on the left and/or the right (L/SAS and/or R/SAS, respectively) within the subclavian artery using an ablation catheter introduced via a femoral arterial sheath. Stimulation involved up to 70 V, 10 Hz, and a 2- to 4-millisecond pulse width for 15 to 30 seconds. Invasive blood pressure (BP), heart rate, and electrophysiological parameters were recorded. A positive response was a ≥10% increase in BP or heart rate from baseline.

Results: Seventeen patients (median age 60 years [quartile 1-quartile 3: 58-67 years];11 male subjects; paroxysmal AF duration 24 months [quartile 1-quartile 3: 10-60 months) underwent the stimulation protocol before their clinical AF ablation procedure. A positive hemodynamic response was observed in 11 patients; of these, arrhythmia was inducible in 5 patients. The median sinus cycle length decreased after stimulation, and there was a larger decrease with R/SAS (L/SAS 1,008 milliseconds to 926 milliseconds [P = 0.037] vs R/SAS 1,029.5 milliseconds to 917 milliseconds [P = 0.005]). Both L/SAS and R/SAS led to a notable increase in median systolic BP (L/SAS 81 mm Hg to 128 mm Hg [P = 0.005] vs R/SAS 85 mm Hg to 104 mm Hg [P = 0.007]) and a similar trend in diastolic BP. In addition, there was a demonstrable decrease in interatrial conduction time and increase in P-wave dispersion.

Conclusions: This study represents the first successful application of selective SAS in humans. The SA is a potentially important site for targeted autonomic neuromodulation therapy.