[Inborn long QT-syndrome in childhood: clinical presentation and treatment]

During the last decade, the understanding of the long QT-syndrome (LQTS) as an inherited arrhythmogenic disease has dramatically increased. The LQTS has been recognized to be a heterogeneous family of ion-channel disorders caused by numerous mutations in at least six distinct gene loci, thus, explaining the prolongation of the myocardial repolarization. Consecutive studies of the LQTS advanced our knowledge of pathophysiology, clinical course and possible therapeutic impact.    As a genetically determined disorder the clinical manifestation of the LQTS naturally starts in childhood. In 34% of the children, syncope or cardiac arrest was found to occur before the age of 15 years. In addition, 54% of all LQTS patients who died from sudden cardiac death were less than 20years old.    Most cases in children are identified by the detection of a prolonged QT interval while evaluating unexplained cases of syncope or by family investigations of an index patient. In children more than in adults, however, normal values of QT interval duration are dependent from age, gender, heart rate and circadian variations. Therefore, the moreover applied correction formulas for the QT interval to heart rate ratio have to be used with caution in the pediatric setting. A useful and reliable tool for the analysis of QT duration, QT patterns, and its circadian variation is multilead digital Holter recordings. The determination of the diagnosis is based on clinical findings according to the criteria of the "International LQTS Registry". Genetic investigations, however, are actually diagnostic in about 50% of the patients, but are not effective as a clinical screening tool.    The genetically determined LQTS types (LQT1-LQT6) differ significantly in terms of reaction to triggering stimuli that may induce life-threatening arrhythmias and their response to treatment. In LQT1, physical stress will more likely induce Torsades de Pointes than in the LQT3, which is more sensitive to emotional stress. The typical LQTS treatment is life-long medication with beta blocking agents; however, in LQT3 patients with mutations in the cardiac sodium channel gene, treatment with mexiletine may have advantages. In order to prevent bradycardia or by short-long sequences inducible torsades, the use of implantable pacemakers is recommended. Stellectomy to minimize cardiac adrenergic susceptibility has proven to be less effective in children. Recently, the rapid technical improvement of implantable defibrillators led to a more frequent use of these devices in children.    In order to sufficiently manage pediatric LQTS patients in the future and to reduce the risk of sudden cardiac death due to inherited arrhythmias, a national and international multicenter approach is necessary.