Bradycardia and asystole with the use of vagus nerve stimulation for the treatment of epilepsy:: A rare complication of intraoperative device testing

Purposes: A 56-year-old man with mild mental retardation, right congenital hemiparesis, and refractory partial seizures was referred for vagus nerve stimulation (VNS). Methods: Routine lead diagnostic testing during the surgical procedure (1.0 mA, 20 Hz, and 500 mu s, for similar to 17 s) resulted, during the initial two stimulations, in a bradycardia of similar to 30 beats/min. A third attempt led to transient asystole that required atropine and brief cardiopulmonary resuscitation. Results: The procedure was immediately terminated, the device removed, and the patient recovered completely. A postoperative cardiologic evaluation, including an ECG, 24-h Holter monitor, echocardiogram, and a tilt-table test, was normal. Conclusions: Possible mechanisms for the bradycardia/asystole include stimulation of cervical cardiac branches of the vagus nerve either by collateral cur rent spread or directly by inadvertent placement of the electrodes on one of these branches; improper plugging of the electrodes into the pulse generator, resulting in erratic varying intensity of stimulation; reverse polarity; and idiosyncratic-type reaction in a hypersusceptible individual. The manufacturer reports the occurrence rate in similar to 3,500 implants for this intraoperative event to be approximately one in 875 cases or 0.1%.