Clinical and histopathological studies in children with supraventricular tachycardia.

To determine whether myocardial changes in patients with supraventricular tachycardia (SVT) are primary or secondary to persistent tachycardia, 11 patients with SVT were studied. These patients were divided into 2 groups with respect to the type of SVT. Group I consisted of 5 patients with incessant SVT and one with multifocal atrial tachycardia, while group II consisted of 4 patients with paroxysmal supraventricular tachycardia and one with short-run supraventricular premature contraction. All of the patients underwent electrophysiological study and endomyocardial biopsy from the right ventricle following routine cardiac catheterization. In group II, there were no significant abnormalities in the clinical and hemodynamic parameters. In group I, 3 patients had clinical features of dilated cardiomyopathy including abnormal ECG, chest X-ray and hypokinesis on left ventriculography. Induction and termination of SVT were possible in 2 patients in group I and in 4 of the 5 patients in group II. The only significant histologic difference between group I and group II was fibrosis. A high incidence of histopathological abnormalities, such as hypertrophy, degeneration, interstitial fibrosis and disarray was observed in both groups. The incidence of significant pathology was higher in group I than in group II. Almost all of the patients were given antiarrhythmic drugs. One patient underwent a successful surgical procedure and normal cardiac function returned after resection of the foci of the right atrium. Our present results suggest that patients with SVT who have incessant or recurrent SVT should undergo not only intracardiac electrophysiologic study but also endomyocardial biopsy for the evaluation of myocardial damage, since SVT might be the initial sign of cardiomyopathy.