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.
Howley
Lisa W
LW
Section of Pediatric Cardiology University of Colorado, Denver, The Children's Hospital, Aurora, Colorado 80045, USA.
DI Maria
Michael
M
Bailey
Amy
A
Schaffer
Michael S
MS
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