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 s timulation (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 att empt led to transient asystole that required atropine and brief cardiopulmo nary resuscitation. Results: The procedure was immediately terminated, the device removed, and the patient recovered completely. A postoperative cardiologic evaluation, i ncluding an ECG, 24-h Holter monitor, echocardiogram, and a tilt-table test , was normal. Conclusions: Possible mechanisms for the bradycardia/asystole include stimu lation 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 g enerator, resulting in erratic varying intensity of stimulation; reverse po larity; and idiosyncratic-type reaction in a hypersusceptible individual. T he manufacturer reports the occurrence rate in similar to 3,500 implants fo r this intraoperative event to be approximately one in 875 cases or 0.1%.