Follow-Up of 316 Molecularly Defined Pediatric Long-QT Syndrome Patients Clinical Course, Treatments, and Side Effects

Background— Inherited long-QT syndrome (LQTS) is associated with risk of sudden death. We assessed the clinical course and the fulfillment of current treatment strategies in molecularly defined pediatric LQTS type 1 and (LQT1) and type 2 (LQT2) patients. Methods and Results— Follow-up data covering a mean of 12 years were collected for 316 genotyped LQT1 and LQT2 patients aged 0 to 18 years. No arrhythmic deaths occurred during the follow-up. Finnish KCNQ1 and KCNH2 founder mutations were associated with fewer cardiac events than other KCNQ1 and KCNH2 mutations (hazard ratio [HR], 0.33; P =0.03 and HR, 0.16; P =0.01, respectively). QTc interval ≥500 ms increased the risk of cardiac events compared with QTc <470 ms (HR, 3.32; P =0.001). Treatment with β-blocker medication was associated with reduced risk of first cardiac event (HR, 0.23; P =0.001). Noncompliant LQT2 patients were more often symptomatic than compliant LQT2 patients (18% and 0%, respectively; P =0.03). Treatment with implantable cardioverter defibrillator was rare (3%) and resulted in reinterventions in 44% of cases. Conclusions— Severe cardiac events are uncommon in molecularly defined and appropriately treated pediatric LQTS mutation carriers. β-Blocker medication reduces the risk of cardiac events and is generally well tolerated in this age group of LQTS patients.