Neonatal Long QT Syndrome Type 3 Predicted by Positive Lidocaine Challenge


Address for reprint: Michael S. Schaffer, M.D., The Children's Hospital, 13123 East 16th Avenue, B100, Aurora, CO 80045. Fax: 720-777-7288; e-mail:


A female infant presented with bradycardia and an electrocardiogram demonstrating 2:1 atrioventricular depolarization, a prolonged QT interval, and T wave alternans. After propranolol therapy was initiated, a lidocaine challenge was performed with progressive shortening of the QT interval. This positive lidocaine challenge prompted clinical suspicion of long QT syndrome type 3 (LQT3) and early initiation of mexiletine therapy. Subsequent genetic testing confirmed the infant's diagnosis of LQT3. (PACE 2010; 33:377–379)