• Fan Wang, Jinqiu Liu, Li Hong, Bo Liang, Claus Graff, Yanzong Yang, Michael Christiansen, Søren-Peter Olesen, Li Zhang, and Jørgen K Kanters.
• Laboratory of Experimental Cardiology, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
• Heart Rhythm. 2013 Oct 1; 10 (10): 1500-6.

BackgroundLong QT syndrome type 13 (LQT13) is caused by loss-of-function mutation in the KCNJ5-encoded cardiac G-protein-coupled inward rectifier potassium channel subtype 4 protein. The electrocardiographic (ECG) features of LQT13 are not described yet.ObjectiveTo describe for the first time in detail the phenotype-genotype relationship of the ECG and clinical features in patients with LQT13.MethodsThe 12-lead ECGs, 24-hour Holter recordings, and clinical information from KCNJ5-G387R mutation carriers of a fourth-generation Han Chinese family with LQT13 and a group of healthy Chinese individuals were analyzed.ResultsCompared with the analysis of the healthy group (n = 8), age- and sex-matched pair analysis revealed that the mutation carriers (n = 8) had ventricular repolarization abnormality results in the prolongation of corrected QT and QTpeak intervals (P < .01); greater combined measure of repolarization morphology (T-wave morphology combination score) based on asymmetry, flatness, and notch (P < .01); and reduced low frequency/high frequency ratio of heart rate variability (P < .01) as a reflection of cardiac autonomic imbalance. Mean heart rate, time domain parameters of heart rate variability, time interval from T-wave peak to T-wave end, and T-wave amplitude were similar.ConclusionsThis study demonstrates for the first time the ECG features of patients with LQT13. Our data suggest that QTpeak intervals and T-wave morphology combination score may be the better parameters than the corrected QT interval to predict the phenotype-genotype relationship in patients with LQT13.© 2013 Heart Rhythm Society. All rights reserved.

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