Effects of levothyroxine therapy on left and right ventricular function in neonates with congenital hypothyroidism: a tissue Doppler echocardiography study.

Cardiac function is impaired in adults or children with hypothyroidism and it can be reversed by levothyroxine (L-T(4)) substitution therapy. However, only a few studies are available on left and right ventricular function in neonates with congenital hypothyroidism (CH), most of which were performed with standard echocardiography. The aim of this study was to investigate the effects of L-T(4) substitution therapy on left and right ventricular function in neonates with CH, measured with tissue Doppler echocardiography (TDE) and conventional echocardiography. Fifty neonates (27 females and 23 males) with CH and 35 normal neonates (19 females and 16 males) underwent conventional echocardiography and TDE. On TDE, peak mitral and tricuspid annular systolic (Sa) velocity, peak early (Ea) and late (Aa) mitral and tricuspid annular diastolic velocity were measured, and the Ea/Aa ratio was calculated. All the biochemical tests and echocardiographic evaluations were reevaluated after 1 month of replacement therapy. In CH neonates, TDE showed that CH neonates had significantly lower Sa, Ea, and Ea/Aa of both left and right ventricles (P<0.001, respectively). However, Aa of left and right ventricles did not differ significantly. After 1 month of substitutive therapy, CH neonates showed a significant increase of Sa and Ea and a subsequent increase of the Ea/Aa ratio (P<0.001, respectively). Our findings suggest that neonates with CH suffer from right ventricular subclinical systolic and diastolic dysfunction in addition to left ventricular dysfunction. Early L-T(4) substitution therapy is able to reverse the impairment of cardiac function.