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Clinical Science (2009) Immediate Publication, doi:10.1042/CS20080528
Long QT syndrome and associated gene mutation carriers in Japanese children: Results from ECG screening examination
Kenshi Hayashi, Noboru Fujino, Katsuharu Uchiyama, Hidekazu Ino, Kenji Sakata, Tetsuo Konno, Eiichi Masuta, Akira Funada, Yuichiro Sakamoto, Toshinari Tsubokawa, Keisuke Nakashima, Li Liu, Haruhiro HIgashida, Yoshitake Hiramaru, Masami Shimizu and Masakazu Yamagishi
Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan. kenshi@med.kanazawa-u.ac.jp
Background: The long QT syndrome (LQTS) is caused by mutations in the cardiac ion channel genes. The prevalence of LQTS in the general population is not well known. Objective: We prospectively estimated the prevalence of LQTS and analyzed the associated mutation carriers in Japanese children. Methods: ECGs were recorded from 7961 Japanese school children (4044 males, mean age 9.9 ± 3.0 years). ECGs were again examined for the children who showed prolonged QTc intervals in the initial ECGs, and their QT intervals were measured manually. An LQTS score was determined by Schwartz’s criteria, and ion channel genes were analyzed. In vitro characterization of identified mutants was performed by heterologous expression experiments. Results: Three subjects were assigned to a high probability of LQTS (3.5 ≤ LQTS score), and 8 to an intermediate probability (1.0 < LQTS score ≤ 3.0). Genetic analysis of these 3 subjects identified three HERG mutations (M124T, 547-553 del GGCGGCG, 2311-2332 del / ins TC). In contrast, no mutation was identified in the 15 subjects with a low probability. Electrophysiological studies showed that both the M124T and the 547-553 del HERG did not suppress the wild type HERG channel in a dominant negative manner. Conclusion: These results demonstrate that, in a random sample of healthy Japanese children, the prevalence of a high probability of LQTS is 0.038% (3/7961), and that LQTS mutation carriers can be identified in at least 0.038% (1/2653). Further, large-scale genetic studies will be needed to clarify the real prevalence of LQTS by gene carrier status, since the present study may have underestimated it.
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