Tachycardias in children originating in the right ventricular outflow tract: lack of clinical features predicting the presence and severity of the histopathological substrate

The aim was to determine whether the clinical features of tachycardias orig inating from the right ventricular outflow tract in children with an appare ntly normal heart could predict the presence and the severity of the histop athological substrate. Thirteen children (median age 6 years; range 6 month s-12 years) with tachycardia originating from the right ventricular outflow tract of apparently normal hearts, were assessed by echocardiography, hear t catheterization with angiography, endomyocardial biopsy (13 patients) and magnetic resonance imaging (MRI) (nine patients). Tachycardia was symptoma tic in six and sustained in nine. Endomyocardial biopsy and MRI revealed ac ute myocarditis in five patients (38%), fatty infiltration of the right ven tricle in two (15%), and:minor histologic abnormalities in three (23%). Myo carditis was diagnosed in three of nine patients with sustained ventricular tachycardia, as opposed to two of four with non-sustained tachycardia (p = NS); in three of six symptomatic versus two of seven asymptomatic patients (p = NS); and in two of eight patients in whom ventricular tachycardia was induced during exercise testing as opposed to one of three in which ir was not inducible (p = NS). A histopathological substrate was found in six of nine patients with sustained ventricular tachycardia, and in all four with non-sustained tachycardia (p = NS); in five of six patients with symptoms v ersus five of seven asymptomatic patients (p = NS); and in five of eight wi th inducible ventricular tachycardia during exercise testing versus all thr ee in whom it was not inducible (p = NS). The mean rate of tachycardia was 184 +/- 39 beats min(-1) in patients with myocarditis, as opposed to 171 +/ - 48 in patients without myocarditis (p = NS); and 163 +/- 33 in patients w ith a histopathological substrate compared with 210 +/- 65 in patients with out a histopathological substrate (p = NS). It is concluded that a histopat hological substrate is present in the greater majority of children affected by the so-called right ventricular outflow tract tachycardia, but that the ,clinical features of the tachycardia do not predict the presence and the s everity of this histopathological substrate.