Heritability in a SCN5A-mutation founder population with increased female susceptibility to non-nocturnal ventricular tachyarrhythmia and sudden cardiac death

BACKGROUND: Heritable cardiac-sodium channel dysfunction is associated with various arrhythmia syndromes, some predisposing to ventricular fibrillation. Phenotypic diversity among carriers of identical-by-descent mutations is often remarkable, suggesting influences of genetic modifiers.OBJECTIVE: The purpose of this study was to identify a unique SCN5A-mutation founder population with mixed clinical phenotypes and sudden cardiac death, and to investigate the heritability of electromechanical traits besides the SCN5A-mutation effect.METHODS: The 16-generation founder population segregating SCN5A c.4850_4852delTCT, p.(Phe1617del), was comprehensively phenotyped. Variance component analysis was used to evaluate the mutation's effects and assess heritability.RESULTS: In 45 p.(Phe1617del) positives, the mutation associated strongly with QTc prolongation (472 ± 60 ms vs 423 ± 35 ms in 26 mutation negatives; P P P P = .006). p.(Phe1617del) was an important determinant of QTcbaseline, QTcmax, and EMW, explaining 18%, 28%, and 37%, respectively, of the trait’s variance. Significant heritability was observed for PQ interval (P = .003) after accounting for the p.(Phe1617del) effect.CONCLUSION: This SCN5A-p.(Phe1617del) founder population with phenotypic divergence and overlap reveals long-QT syndrome-related and arousal-evoked ventricular tachyarrhythmias with a female preponderance. Variance component analysis indicates additional genetic variance for PQ interval hidden in the genome, besides a dominant p. .(Phe1617del) effect on QTc and EMW.