THE ELECTROPHYSIOLOGIC EFFECTS OF VOLATILE ANESTHETICS AND SUFENTANILON THE NORMAL ATRIOVENTRICULAR-CONDUCTION SYSTEM AND ACCESSORY PATHWAYS IN WOLFF-PARKINSON-WHITE SYNDROME

Background: The effects of volatile agents and sufentanil anesthesia o n the electrophysiologic properties of the accessory pathway and on th e incidence of intraoperative tachyarrhythmias in patients with Wolff- Parkinson-White syndrome are unknown. Therefore, we studied these agen ts for their use in patients undergoing ablative procedures or requiri ng a general anesthetic for other surgeries. Methods: Twenty-one patie nts with Wolff-Parkinson-White syndrome undergoing surgical ablation w ere anesthetized with sufentanil (20 mu g/kg), lorazepam (0.06 mg/kg), and vecuronium (20 mg). After sternotomy, the electrophysiologic stud y during antegrade stimulation consisted of the effective refractory p eriod of the right atrium, atrioventricular node, and accessory pathwa y; the shortest cycle length of the atrioventricular node and accessor y pathway; and the coupling interval. During retrograde stimulation, t he effective refractory period of the right ventricle and accessory pa thway and the shortest cycle length of the accessory pathway were meas ured and compared to preoperative electrophysiologic values. Patients then were randomized to receive 1 MAC of halothane, isoflurane, or enf lurane, and the electrophysiologic study was repeated. Results: Sufent anil-lorazepam caused mild prolongation (P<0.05) of the effective refr actory period of the accessory pathway and the shortest cycle length o f the atrioventricular node. Enflurane and isoflurane significantly pr olonged all parameters related to refractoriness during antegrade cond uction, with enflurane having the largest effect. During retrograde co nduction, isoflurane prolonged the effective refractory period of the right ventricle and accessory pathway and the shortest cycle length of the accessory pathway, whereas enflurane prolonged only the accessory pathway effective refractory period and shortest cycle length. Haloth ane had the least effect on refractoriness, causing significant prolon gation of the atrioventricular node effective refractory period and th e shortest cycle length of the accessory pathway only during antegrade conduction. The coupling interval, a measure of the period of vulnera bility to supraventricular tachycardia, was prolonged only by halothan e and isoflurane. Supraventricular tachycardia was still obtainable in all patients. Conclusions: Sufentanil-lorazepam has no clinically sig nificant effect on the electrophysiologic expression of the accessory pathway. Of the volatile agents, enflurane most, isoflurane next, and halothane least increased refractoriness within the accessory and atri oventricular pathways. Therefore, administration of these volatile age nts during ablative procedures may confound interpretation of postabla tive studies used to determine the success of ablation treatment. Conv ersely, in patients with preexcitation syndrome requiring general anes thesia for nonablative procedures, volatile agents may reduce the inci dence of perioperative tachyarrhythmias because of their effects on re fractoriness. Enflurane would be the agent of choice because it increa ses refractoriness the most without prolonging the coupling interval.