[Influence of congenital hypothyroidism on left ventricular function of neonates].

OBJECTIVE: To evaluate left ventricular function in neonates with congenital hypothyroidism (CH) and its correlation with thyroid hormones serum levels.

METHODS: M-mode echocardiography [left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS)], pulse wave Doppler [the peak early diastolic mitral inflow velocity (Em), the peak late diastolic mitral inflow velocity (Am)], quantitative tissue velocity imaging (QTVI) [the systolic peak mitral annular velocity (sm), the early diastolic peak mitral annular velocity (em), the late diastolic peak mitral annular velocity (am)] and tissue tracking imaging (TTI) [the systolic mitral annular displacement (MAD)] were evaluated in 35 neonates with congenital hypothyroidism aged 15-28 days and 30 normal neonates in this study. Correlation analysis was also made between left ventricular function and serum TT3, TT4 and TSH levels.

RESULTS: Left systolic function parameters (LVEF, LVFS, sm and MAD) were 0.62 +/- 0.08, (28.21 +/- 5.31)%, (2.58 +/- 0.59) cm/s and (0.27 +/- 0.07) cm, respectively, in CH group, and 0.67 +/- 0.06, (31.16 +/- 4.13)%, (3.24 +/- 0.52) cm/s and (0.41 +/- 0.08) cm in control group (P < 0.05, P < 0.01). Left diastolic function parameters (Am, Em/Am, em/am, Em and em) were (0.59 +/- 0.10) m/s, 0.98 +/- 0.18, 0.82 +/- 0.40, (0.57 +/- 0.11) m/s and (2.83 +/- 1.48) cm/s, respectively, in CH group, and (0.65 +/- 0.10) m/s, 1.14 +/- 0.20, 1.25 +/- 0.33, (0.73 +/- 0.11) m/s and (4.46 +/- 1.29) cm/s in control group (P < 0.05, P < 0.01). MAD, sm, Em and em in CH group were greatly lower than that in control group (P < 0.001). Left systolic function (LVEF, sm, MAD) and diastolic function (Em, Am, em, em/am) were positively correlated with TT3, TT4 serum levels (P < 0.05, P < 0.01), and negatively with TT4 serum levels (P < 0.05, P < 0.01). MAD, Em and em were highly correlated with TT4, TSH serum levels (r = 0.700, r = 0.564, r = 0.593, r = 0.564, P < 0.001; r = -0.674, r = -0.521, r = -0.578, r = -0.632, P < 0.001).

CONCLUSIONS: Neonates with CH have lower left systolic and diastolic function. Left ventricular function was affected by thyroid hormones. QTVI and TTI are more sensitive parameters in evaluating left ventricular function of neonates with congenital hypothyroidism than conventional echocardiography.