Objective: QT interval prolongation of unknown aetiology is common in Turner syndrome (TS). This study set out to explore the presence of known pathogenic long QT (LQT) mutations in TS and to examine the corrected QT interval (QTc) over time and relate the findings to the TS phenotype.
Methods: Adult females with TS (n=102) were examined thrice with a mean follow-up of 4.7±0.5 years, and 68 age-matched healthy controls were examined once. QTc was measured by one blinded reader (intra-reader variability: 0.7%), and adjusted for influence of heart rate by Bazetts (bQTc) and Hodgess formula (hQTc). The prevalence of mutations in genes related to Long QT syndrome (LQTS) was determined in females with TS and a QTc >432.0 ms. Echocardiographic assessment of aortic valve morphology, 24-h blood pressures and blood samples were done.
Results: The mean hQTc in females with TS (414.0±25.5 ms) compared to controls (390.4±17.8 ms) was prolonged (P<0.001) and did not change over time (416.9±22.6 vs 415.6±25.5 ms; P=0.4). 45,X karyotype was associated with increased hQTc prolongation compared to other TS karyotypes (418.2±24.8 vs 407.6±25.5 ms; P=0.03). In females with TS and a bQTc >432 ms, seven had mutations in major LQTS-genes (SCN5A and KCNH2) and one in a minor LQTS-gene (KCNE2).
Conclusion: The prevalence of mutations in major LQTS genes was strikingly high for females with TS and the longest QTc interval.