Neonatal long QT syndrome type 3 predicted by positive lidocaine challenge.
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.
Section of Pediatric Cardiology University of Colorado, Denver, The Children's Hospital, Aurora, Colorado 80045, USA.
Lisa W
LW
Howley
Michael
M
DI Maria
Amy
A
Bailey
Michael S
MS
Schaffer
D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D001919:Bradycardia / Q000175:diagnosis; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008012:Lidocaine; D008133:Long QT Syndrome / Q000175:diagnosis*; D008801:Mexiletine / Q000627:therapeutic use; D011433:Propranolol / Q000627:therapeutic use
D000889:Anti-Arrhythmia Agents; D008801:Mexiletine; D008012:Lidocaine; D011433:Propranolol