Detection and evaluation of asymptomatic myocarditis in schoolchildren: report of four cases.

STUDY OBJECTIVE Data on the prevalence of myocarditis in children are limited. Autopsy studies have shown that myocarditis is often undiagnosed. We attempted to investigate the clinical features of asymptomatic myocarditis in four schoolchildren detected during a mass ECG screening in schoolchildren. DESIGN AND SETTING To evaluate asymptomatic myocarditis, we clinically examined 12 schoolchildren who were referred to Shiga University of Medical Science Hospital, Otsu, Japan, because of abnormal ST or T waves detected during ECG screening. None of the 12 children had experienced any episodes suggesting cardiac disease or Kawasaki disease. Cardiac function and myocardial viability were assessed by two-dimensional echocardiography (2-DE), thallium-201 (201Tl) myocardial scintigraphy, and cardiac catheterization. Endomyocardial biopsy specimens were examined histologically. PATIENTS Endomyocardial biopsy specimens revealed histologic evidence of myocarditis in 4 of the 12 children with abnormal ST or T waves. RESULTS Abnormal tracer perfusion was observed on 201Tl myocardial scintigrams in these four children, but the results of coronary arteriography were normal. 2-DE showed left ventricular hypokinesis in one child and left ventricular enlargement in one of the four children with histologic evidence of myocarditis. A second endomyocardial biopsy specimen was obtained in two of four children, showing persistent myocarditis in one child. CONCLUSIONS This type of screening program and indepth evaluation using 2-DE and 201Tl myocardial scintigraphy appear to be helpful in identifying children with myocarditis. The present histologic investigations suggested that even asymptomatic myocarditis might result in persistent heart damage.