• Mikael Koponen, Annukka Marjamaa, Anita Hiippala, Juha-Matti Happonen, Aki S Havulinna, Veikko Salomaa, Annukka M Lahtinen, Taina Hintsa, Matti Viitasalo, Lauri Toivonen, Kimmo Kontula, and Heikki Swan.
• From the Heart and Lung Center, Helsinki University Central Hospital (M.K., A.M., M.V., L.T., H.S.), Children's Hospital, Helsinki University Central Hospital (A.H., J.-M.H.), Department of Medicine, Helsinki University Central Hospital (A.M.L., K.K.), and Institute of Behavioural Sciences, Psychology (T.H.), University of Helsinki, Helsinki, Finland; and Department of Health, National Institute for Health and Welfare, Helsinki, Finland (A.S.H., V.S.). mikael.koponen@helsinki.fi.
• Circ Arrhythm Electrophysiol. 2015 Aug 1; 8 (4): 815-23.

BackgroundInherited 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 ResultsFollow-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.ConclusionsSevere 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.© 2015 American Heart Association, Inc.

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