Neural Control of Ventricular Rate in Ambulatory Dogs With Pacing-Induced Sustained Atrial Fibrillation

Abstract

Background— We hypothesize that inferior vena cava–inferior atrial ganglionated plexus nerve activity (IVC-IAGPNA) is responsible for ventricular rate (VR) control during atrial fibrillation (AF) in ambulatory dogs. Methods and Results— We recorded bilateral cervical vagal nerve activity (VNA) and IVC-IAGPNA during baseline sinus rhythm and during pacing-induced sustained AF in 6 ambulatory dogs. Integrated nerve activities and average VR were measured every 10 seconds over 24 hours. Left VNA was associated with VR reduction during AF in 5 dogs (from 211 bpm [95% CI, 186–233] to 178 bpm [95% CI, 145–210]; P <0.001) and right VNA in 1 dog (from 208 bpm [95% CI, 197–223] to 181 bpm [95% CI, 163–200]; P <0.01). There were good correlations between IVC-IAGPNA and left VNA in the former 5 dogs and between IVC-IAGPNA and right VNA in the last dog. IVC-IAGPNA was associated with VR reduction in all dogs studied. Right VNA was associated with baseline sinus rate reduction from 105 bpm (95% CI, 95–116) to 77 bpm (95% CI, 64–91; P <0.01) in 4 dogs, whereas left VNA was associated with sinus rate reduction from 111 bpm (95% CI, 90–1250) to 81 bpm (95% CI, 67–103; P <0.01) in 2 dogs. Conclusions— IVC-IAGPNA is invariably associated with VR reduction during AF. In comparison, right or left VNA was associated with VR reduction only when it coactivates with the IVC-IAGPNA. The vagal nerve that controls VR during AF may be different from that which controls sinus rhythm.