Exercise Stress Testing: Diagnostic Utility in the Evaluation of Long QT Syndrome

Congenital long QT syndrome (LQTS), an inherited disorder of ventricular repolarization, is characterized by a prolonged QT interval and T-wave morphological changes on the surface electrocardiogram (EKG) with associated symptoms of syncope, seizures, cardiac arrest, and sudden death. Multiple studies in adults and a few in pediatric patients have demonstrated the value of performing exercise stress tests (EST) as a diagnostic tool in the evaluation of patients with suspected LQTS. As LQTS demonstrates reduced penetrance and many patients are asymptomatic, affected individuals with LQTS can be erroneously considered unaffected if only clinical features and resting EKG are utilized for diagnostic purposes. EST—and specifically—QTc interval prolongation during recovery after EST has been demonstrated to be a sensitive screening test for LQTS.