Abstracts

Vagus Nerve Stimulation (VNS) is an important therapeutic option for individuals with refractory epilepsy. We reviewed three cases of ventricular asystole with complete heart block that occurred during intraoperative lead test. The purpose of these case reports is to identify the specific type of cardiac abnormality associated with VNS stimulation and to identify individuals at risk.
After IRB approval, the epilepsy database at our institution was reviewed. Thirty five patients who underwent VNS therapy were identified and their charts reviewed. Two patients with cardiac conduction abnormality during the intraoperative lead test are reviewed below. A third patient from a another institution was also included.
A 53 year old man with static encephalopathy, atypical absence and generalized tonic clonic seizure since age four failed multiple conventional and newer antiepileptic drugs (AEDs). Interictal EEG was abnormal with multifocal epileptiform discharges. He underwent VNS placement and during the lead test with standard stimulation parameters (1 mAmp, 500 us, 20 Hz) he developed a fifteen second period of complete heart block with ventricular asystole. The stimulation was stopped with normalization of heart rate and rhythm. A second trial resulted in the same conduction defect. Postoperative EKG, echocardiogram, and cardiac evaluation was unremarkable.
A 40 year old man with static encephalopathy with intractable complex partial, myoclonic and generalized seizures who had failed multiple AEDs underwent VNS implantation and preliminary lead tests showed high impedance. After corrective measures were taken, lead test with standard stimulation parameters resulted in ventricular asystole that lasted twelve seconds and stimulation was quickly terminated. In both these patients there was no preoperative or post-operative cardiac abnormality noted. Both these patients were on [underline]carbamazepine [/underline]and valproic acid.
A 42 year old woman with diabetes, hypertension and refractory complex partial seizures developed an nine second period of ventricular asystole with hypotension during the lead test at standard stimulation parameters. A preoperative EKG had shown a first degree heart block. Subsequent cardiac evaluation was unremarkable.
There are few published case reports of asystole associated with vagus nerve stimulation for epilepsy. Our cases are important because we were able to obtain cardiac rhythm strips during these episodes which showed a normal, regular [quot]p[quot] wave (atrial rhythm) with no ventricular activity indicating a complete AV nodal block. The occurrence of this complication in selected patients may be related to autonomic dysfunction. Further studies are needed to look at the contributing role of AEDs (such as carbamazepine), anesthesia and concomitant neurologic morbidity in development of this complication.