Pediatric Cardiology and Cardiac Surgery
Vol.26 No.1 2010 (67-72)
Mari Iwamoto,1 Takashi Nishizawa,1 Shigeo Watanabe,1 Yasuhiro Ichikawa,1 Nao Shimizu,1 Kazuko Yamaguchi,1 Tohru Akaike,2 Utako Yokoyama,2 Kiyohiro Takigiku,3 Takuma Sakon,4 Kiyoshi Yasui,5 Toshimitsu Shibata,6 Ichiro Niimura,7 and Shunpei Yokota8)
1)Department of Pediatric Cardiology, Yokohama City University Hospital, 2)Cardiovascular Research Institute, Yokohama City University School of Medicine, Yokohama, 3)Department of Cardiology, Nagano Pediatric Hospital, Nagano, 4)Department of Pediatrics, Fujisawa City Hospital, 5)Yasui Clinic, 6)Shibata Clinic, 7)Niimura Clinic, 8)Department of Pediatrics, Yokohama City University School of Medicine, Kanagawa, Japan
Background: Symptoms (syncope, cardiac arrest, sudden death) in long QT syndrome (LQTS) are triggered by exercise, emotion, or sleep/rest arousal. QT responses to heart rate during exercise are not good in LQTS patients who have symptoms during exercise. We estimated other indices of ECG during exercise in LQTS patients.
Methods: Ten cases of LQTS with cardiac events during exercise and 10 controls (post mucocutaneous lymph-node syndrome (MCLS) and normal coronary artery) were examined by exercise ECG. RR interval, QT interval, and QT peak: QTp, T peak-end: Tp-e were measured, and corrected using the Fridericia formula (QT/RR1/3).
Results: QTc was increased to maximum values at the recovery 2–3 min. phase in the LQTS subjects (17% increased compared with rest), and in control cases QTc was not increased during exercise. Tp-e c were increased during exercise in LQTS, and improved after β-blocker therapy.
Conclusion: ECG parameters had characteristic changes during exercise in LQTS who have exercise-induced syncope. Those changes may be an important factor for TdP.