Abstract
Background: Anesthesia sometimes suppresses ventricular tachyarrhythmias (VT) resistant to conventional pharmacological treatment. Methods and Results: To know (1) whether deep anesthesia inhibits abnormal repolarization-related VT and (2) if α2-adrenoreceptor (AR) agonistic action is associated with the antiarrhythmic effect of anesthetics, the incidence of VT in a rabbit model of acquired long QT syndrome using different anesthetic regimen was assessed. In Study 1 (n=30), 15 rabbits were lightly anesthetized with ketamine (123±46mg/kg) and an α2-AR agonist, xylazine (9.4±3.0mg/kg), while combination of these anesthetics at high doses were used in the other 15 rabbits (343±78mg/kg and 38.9±3.0mg/kg). Administration of α1-AR stimulant, methoxamine and nifekalant (Ikr blocker) caused VT in all lightly anesthetized rabbits. In contrast, VT was observed only in 1 of the 15 deeply anesthetized rabbits (P<0.01). In Study 2 (n=15), 10 rabbits were anesthetized with high-dose ketamine and low-dose xylazine. In the other 5 rabbits, low-dose ketamine and high-dose xylazine were used. QTc interval in the latter was longer than that of the former (399±56ms vs. 494±57ms, P<0.01). Although no VT appeared in high/low-rabbits, VT occurred in 3 out of 5 low/high-rabbits (P<0.05). Conclusions: These results suggest that (1) deep anesthesia suppresses abnormal repolarization-related VT and (2) antiarrhythmic effect of anesthesia on this type of VT is not dependent on α2-AR agonistic action. (Circ J 2011; 75: 89-93)
