For the early detection of myocardial ischemia in patients with severe involvement of the coronary arteries after Kawasaki disease, a method with high sensitivity and low cost is desirable because these patients require frequent follow-up and diagnostic tests. For this purpose, electrocardiographic, echocardiographic, Holter, and stress testing or angiography are repeated. However, these tests have some limitations due to cost, convenience, or sensitivity. It is uncertain that increased QT dispersion would exactly indicate progression of myocardial ischemia after Kawasaki disease, but this is the first study to present that QT dispersion of > or = 60 ms had higher sensitivity for detection of severe involvement of coronary artery after Kawasaki disease. This study is limited due to the small number of patients; larger prospective studies are required to clarify the usefulness of QT dispersion analysis in detecting the progression of myocardial ischemia after Kawasaki disease.