The congenital long QT syndromes in childhood

Department of Cardiology, Royal Children's Hospital, Melbourne, Victoria, Australia.

Twenty-three children and young persons with a congenital long QT syndrome were identified; the median age at the time of referral was 10 years (range 4 days to 19 years) and 14 patients (61%) had a family history of the syndrome. Among the 19 patients with symptoms, the initial symptom was syncope in 13 (69%), aborted sudden death in 5 (26%) and near drowning in 1 (5%). There were three deaths during a combined follow-up period of 67 patient-years (average annual mortality rate 4.5%). Patients who did not respond to therapy with a beta-adrenergic blocker and those who died were significantly younger than the remaining patients at the time of diagnosis (p less than or equal to 0.05 for both). Analysis of 44 treadmill exercise tests performed by 16 patients revealed significant prolongation of the median corrected QT (QTc) interval in response to exercise, with maximal prolongation present after 2 min of recovery (median QTc interval 0.52 s versus a baseline value of 0.47 s, p less than 0.001). Characteristic changes in T wave configuration were noted in 8 of 15 patients on at least one occasion during ambulatory Holter electrocardiographic monitoring, including T wave alternation in two patients, both of whom died shortly afterward. It is suggested that the congenital long QT syndrome is associated with a significant mortality rate in childhood despite the use of conventional therapy in symptomatic patients. Ambulatory Holter monitoring and treadmill exercise testing may be helpful, both in confirming the diagnosis of a long QT syndrome and in monitoring the adequacy of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				R. L. Verrier and M. E. Josephson Impact of Sleep on Arrhythmogenesis Circ Arrhythm Electrophysiol, August 1, 2009; 2(4): 450 - 459. [Full Text] [PDF]

				G. Cucchiaro and L. A. Rhodes Unusual presentation of long QT syndrome Br. J. Anaesth., June 1, 2003; 90(6): 804 - 807. [Abstract] [Full Text] [PDF]

				A Benatar and T Decraene Comparison of formulae for heart rate correction of QT interval in exercise ECGs from healthy children Heart, August 1, 2001; 86(2): 199 - 202. [Abstract] [Full Text] [PDF]

				J. A. Towbin, Z. Wang, and H. Li Genotype and Severity of Long QT Syndrome Drug Metab. Dispos., April 1, 2001; 29(4): 574 - 579. [Abstract] [Full Text]

				H. Swan, M. Viitasalo, K. Piippo, P.a. Laitinen, K. Kontula, and L. Toivonen Sinus node function and ventricular repolarization during exercise stress test in long QT syndrome patients with KvLQT1 and HERG potassium channel defects J. Am. Coll. Cardiol., September 1, 1999; 34(3): 823 - 829. [Abstract] [Full Text] [PDF]

				A.G. Hermosillo, J.C. Falcon, M.F. Marquez, D. Arteaga, and M. Cardenas Positive head-up tilt table test in patients with the long QT syndrome Europace, January 1, 1999; 1(4): 213 - 217. [Abstract] [PDF]

				B. J. Maron, J. H. Moller, C. E. Seidman, G. M. Vincent, H. C. Dietz, A. J. Moss, J. A. Towbin, H. M. Sondheimer, R. E. Pyeritz, G. McGee, et al. Impact of Laboratory Molecular Diagnosis on Contemporary Diagnostic Criteria for Genetically Transmitted Cardiovascular Diseases: Hypertrophic Cardiomyopathy, Long-QT Syndrome, and Marfan Syndrome : A Statement for Healthcare Professionals From the Councils on Clinical Cardiology, Cardiovascular Disease in the Young, and Basic Science, American Heart Association Circulation, October 6, 1998; 98(14): 1460 - 1471. [Full Text] [PDF]

				M. J. Ackerman and C.-b. J. Porter Identification of a Family With Inherited Long QT Syndrome After a Pediatric Near-drowning Pediatrics, February 1, 1998; 101(2): 306 - 308. [Full Text] [PDF]