定量组织速度成像和组织追踪显像技术评价先天性甲状腺功能减退症新生儿的右心功能

目的应用定量组织速度成像（QTVI）和组织追踪显像（TTI）技术评价先天性甲状腺功能减退症（CH）新生儿在甲状腺素替代治疗前后的右心功能变化,并探讨其临床应用价值。方法应用QTVI和TTI技术离线分析35例正常新生儿以及52例CH新生儿在左旋甲状腺素（L-T4）替代治疗前与治疗1个月后的心尖四腔切面三尖瓣环运动速度曲线和位移曲线,测量收缩期峰值速度（Vs）、收缩期最大位移（D）、舒张早期峰值速度（Ve）、舒张晚期峰值速度（Va）,计算Ve／Va值;常规记录三尖瓣口脉冲多普勒（PWD）血流频谱,测量舒张早期充盈峰值速度（E）,舒张晚期充盈峰值速度（A）,计算E／A值。同时运用化学发光法检测各组患儿的血清促甲状腺素、三碘甲状腺原氨酸总量、甲状腺素总量、游离三碘甲状腺原氨酸和游离甲状腺素水平,并与QTVI、TTI检测指标行Person相关分析。结果CH组新生儿E峰及E／A值低于对照组（均P〈0．001）,但A峰差异无统计学意义（P〉0．05）;QTVI及TTI示,CH组Ve、Ve／Va值、Vs及D均显著低于对照组,差异有统计学意义（均P〈0．001）,而Va差异无统计学意义（P〉0．05）。经L-T4替代治疗后1个月,CH组新生儿Ve、Ve／Va值、Vs、D及E、E／A值分别为（6．92±1．86）cm／s、（1．13±0．22）、（5．92±1．03）cm／s、（0．78±0．17）cm和（61±10）cm／s、（1．1±0．4）,与治疗前比较差异有统计学意义（均P〈0．001）。相关分析显示,Ve、Ve／Va值、Vs、D与三碘甲状腺原氨酸总量、甲状腺素总量TT4、游离三碘甲状腺原氨酸、游离甲状腺素呈显著正相关（均P〈0．01）,与促甲状腺素呈显著负相关（均P〈0．01）。结论CH新生儿的右心收缩与舒张功能均显著低于正常新生儿,早期及时甲状腺素替代治疗可逆转受损的右心功能。应用QTVI及TTI技术检测三尖瓣环运动频谱可定量、准确、有效地评价新生儿右心功能。

Evaluation of right ventricular function by quantitative tissue velocity imaging and tissue tracking imaging in neonates with congenital hypothyroidism

OBJECTIVE: Although several reports documented the association of congenital hypothyroidism (CH) and left ventricular (LV) function in infants or neonates, right ventricular (RV) function in neonates with CH has not been previously studied. The aim of the present study was to assess RV function in neonates with CH before and after thyroxine substitution therapy by quantitative tissue velocity imaging (QTVI) and tissue tracking imaging (TTI). METHODS: Fifty-two neonates aged 18-28 days (25 males and 27 females) with CH and 35 healthy neonates aged 18-28 days (16 males and 19 females) were studied by QTVI, TTI as well as conventional pulsed-wave Doppler echocardiography (PWD). The standard apical four-chamber view for long-axis motion of the right ventricle was used for echocardiographic evaluation. Peak systolic displacement (D), peak systolic velocity (Vs), peak early (Ve) and late (Va) diastolic velocity of tricuspid annule were measured, Ve/Va ratio was calculated as well. Transtricuspid flow velocity during early diastole (E) and late diastole (A) were also measured by pulsed-wave Doppler echocardiography. PWD and E/A ratio were calculated too. For each neonate, serum hormone levels of TSH, TT(3), TT(4), FT(3) and FT(4) were measured with a standard chemiluminescent immunoassay. After 1 month of levothyroxine (L-T(4)) substitution therapy in CH neonates, all the echocardiographic evaluations and biochemical tests were re-evaluated. Correlation analysis was also made between serum thyroid hormones levels and right ventricular function. RESULTS: The indices of right ventricular diastolic function by PWD (E and E/A ratio) in CH group were (45 +/- 10) cm/s and (0.8 +/- 0.3), respectively. Compared with controls, E and E/A ratio in CH neonates were significantly lower (P < 0.001, respectively), while A did not differ between the two groups (P > 0.05). QTVI and TTI showed that right diastolic function (Ve and Ve/Va ratio) as well as right systolic function (Vs and D) in CH group were (3.69 +/- 1.38) cm/s, (0.74 +/- 0.19) cm/s, (4.38 +/- 0.63) cm/s and (0.52 +/- 0.12) cm, respectively. CH neonates had significantly lower Ve, Ve/Va ratio, Vs and D of tricuspid annular velocity (P < 0.001, respectively), whereas there was no significant difference in Va between the two groups (P > 0.05). After 1 month of substitutive therapy, CH neonates showed a significant increase of Ve, Ve/Va ratio, Vs, D, E, and E/A ratio, (6.92 +/- 1.86) cm/s, (1.13 +/- 0.22), (5.92 +/- 1.03) cm/s, (0.78 +/- 0.17) cm, (61 +/- 10) cm/s and (1.1 +/- 0.4), respectively (P < 0.001). Those parameters were positively correlated with serum TT(3), TT(4), FT(3) and FT(4) levels (P < 0.01, respectively), and were negatively correlated with serum TSH levels (P < 0.01, respectively). CONCLUSIONS: Our findings suggest that neonates with CH are associated with right ventricular subclinical systolic and diastolic dysfunction, which can be reversed by early L-T(4) substitution therapy. QTVI and TTI are valuable methods to evaluate right ventricular function in neonates. Systolic and diastolic velocities of the tricuspid annulus measured by QTVI and TTI are useful and accurate to assess RV function in neonates.