Perioperative Torsade de Pointes Ventricular Tachycardia

Abstract

In Response: We appreciate the comment by Broka et al. that central neuraxial anesthesia should be used cautiously in patients with a prolonged QT interval. However, it is important to understand the mechanisms of central neuraxial induced effects on the QT interval and how this affects patients with acquired versus congenital QT prolongation differently. The bradycardia that occurs in approximately 2% of patients after epidural anesthesia [1] is most likely due to a decrease in venous return, which activates up to three possible receptors: low-pressure baroreceptors in the right atrium, pacemaker cells of the myocardium, or mechanoreceptors in the left ventricle (Bezold-Jarisch response) [2,3]. These receptors trigger an increase in vagal tone and bradycardia. In patients with acquired prolonged QT intervals, such as Broka et al.'s, this resulting bradycardia directly causes further prolongation of the QT interval, which could induce torsade de pointes. Additionally, a thoracic sympathetic block from a high epidural causes vagal predominance, which leads to further QT prolongation, independent of heart rate [4,5]. Volume loading and limiting the height of sympathetic block could help reduce the incidence of QT prolongation caused by epidural blockade. Patients with congenital prolonged QT syndrome are at risk of torsade de pointes with sympathetic stimulation because they fail to appropriately shorten the QT interval with sympathetic stimulation [6]. In these patients, an epidural resulting in a high thoracic sympathetic block could reduce the risk of torsade de pointes, as successful treatment has included left cervical-thoracic sympathectomy [7]. It would be wise to avoid epinephrine in the epidural test dose. Stewart J. Lustik, MD Department of Anesthesiology; University of Rochester Medical Center; Rochester, NY 14642 James P. Eichelberger, MD Department of Cardiology; University of Rochester Medical Center; Rochester, NY 14642 Ashwani K. Chhibber, MD Departments of Anesthesiology and Cardiology; University of Rochester Medical Center; Rochester, NY 14642 Oscar Bronsther, MD Department of Transplant Surgery; University of Rochester Medical Center; Rochester, NY 14642