Cardiac abnormalities in children with hyperthyroidism.

The cardiac status of 18 hyperthyroid (HT) children (9 black and 9 white) was evaluated by echocardiography. Mitral regurgitation (MR) was diagnosed clinically in 33% (6 of the 9 blacks). None of the 9 white children had MR. Left ventricular end-diastolic diameter (LVEDD) and volume (LVEDV) did not differ from the predicted normal (PN) based on body surface area and heart rate, except in those with MR where increased LVEDD and LVEDV were noted (p less than 0.02). LV mass was +1.75 standard deviations (sigma) of the PN (p less than 0.01), due to increased wall thickness of LVEDV. Left ventricular output (LVO) was +0.35 sigma PN (p = ns); however, when compared to that of normal children, LVO of HT was higher (p less than 0.001) due to the increased heart rate. Enhanced left ventricular contractility was suggested by increased rate of dimensional change during ejection (peak dD/dt-syst), with a mean value of -11.39 cm/sec as compared to the normal of -9.54 cm/sec (p less than 0.01). A linear multivariate regression equation differentiated the cardiac status of HT from that of normal children. Following treatment to euthyroid state, MR disappeared in 2 and became less in 4 patients. LVO, LV mass, and peak dD/dt-syst also became less. Significant cardiac changes occur in children with hyperthyroidism, which may be reversible in part after euthyroidism is restored.