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Long QT interval syndrome (LQTS) is a potentially fatal condition, characterized by a prolonged QT in terval (usually defined as longer than 440 ms for males and 460 ms for females on the electrocardiogram; Rossenbacker and Priori, 2007) and the development of serious arrhythmias (ventricular tachycardias and tor sade de pointes, which may degenerate into ventricular fibrillation). Hereditary LQTS is predominantly caused by mutations in at least 12 (Lehnart et al., 2007; Tester and Ackerman, 2009) known genes that code for directly or are involved in the function of ion channels in the heart. Recent genomewide association studies suggest that additional genes with small effects on the QT interval may contribute to the significant phenotypic variation seen in this syndrome (Arking et al., 2006; NewtonCheh et al., 2009). Of the 12 ion channel or related genes, mutations in KCNQ1 (LQT1), hERG (LQT2), and SCN5A (LQT3) are the most common, comprising 98 % of all LQTS cases (Napolitano et al., 2005). Correspondence to David Fedida