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 micros, for approximately 17 s) resulted, during the initial two stimulations, in a bradycardia of approximately 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 current 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 approximately 3,500 implants for this intraoperative event to be approximately one in 875 cases or 0.1%.