Effect of cervical vagal nerve stimulation on defibrillation energy: a possible adjunct to efficient defibrillation

The efficacy of electrical defibrillation is considered to be related to the autonomic status. In search of a possible adjunct to enhance the therapeutic performance of an implantable cardioverter-defibrillator. we investigated whether parasympathetic manipulation by cervical vagal nerve stimulation (VNS) increases defibrillation efficacy. The effects of VNS on transcardiac defibrillation threshold (DFT) were assessed in 55 anesthetized dogs. In neurally intact dogs, right and left unilateral VNS at 10 mA for 7 seconds significantly decreased the DFT after 10 seconds of ventricular fibrillation (control: 3.1 +/- 0.9 J, right: 2.1 +/- 0.9 J [delta-35 +/- 12%, P < 0.0001], left: 2.2 +/- 0.8 J [delta-31 +/- 11%, P < 0.0005]), while bilateral VNS did not (2.8 +/- 1.0 J). In dogs with decentralized vagus nerves, both unilateral and bilateral VNS decreased the DFT. The extent of the VNS-induced decrease in DFT was dependent on the current and the duration of stimulation. We conclude that unilateral VNS decreases the DFT, while bilateral VNS paradoxically has no effect on the DFT unless the vagi are decentralized.