先天性甲状腺功能减退症新生儿心电图改变的意义

目的评价先天性甲状腺功能减退症(CH)新生儿的心电图(ECG)改变,及与血清甲状腺激素(TH)水平的相关性,探讨TH减少对新生儿心脏电生理活动的影响。方法对50例CH新生儿(日龄17～28d)和35例健康新生儿(健康对照组)进行常规十二导联ECG检查,分别检测心率(HR)、PR间期(PR)、QT间期(QT)、QRS波电轴(QRSa)、QRS波时限(QRS)、校正QT间期(QTC)等,同时用化学发光法测定血清游离三碘甲状腺原氨酸(FT3)、游离甲状腺素(FT4)、总三碘甲状腺原氨酸(TT3)、总甲状腺素(TT4)和促甲状腺素(FSH)水平,对心电图指标和血TH水平行相关性分析。结果与健康对照组相比,CH组血清FT3、FT4、TT3、TT4水平显著降低,TSH水平显著升高(Pa<0.001);CH组HR显著低于健康对照组,PR及QT较健康对照组显著延长(Pa<0.05),但二组QRSa、QRS及QTC差异均无统计学意义(Pa>0.05)。HR与FT3、FT4呈显著正相关,与TSH呈显著负相关(Pa<0.05);PR间期与FT3、FT4、TT4呈显著负相关,与TSH呈显著正相关(Pa<0.05);但QT、QRS、QRSa及QTC与血TH水平均无明显相关(Pa>0.05)。结论CH可对新生儿窦房结起搏产生显著影响,引起心脏自律性改变,而心肌动作电位、房室传导等电生理活动则尚未受影响。

Change of Electrocardiographic Manifestations of Neonates with Congenital Hypothyroidism and Its Clinical Significance

Objective To assess the changes of electrocardiographic (ECG) manifestations in neonates with congenital hypothyroidism (CH),as well as its correlation with thyroid hormones serum levels and the influence on neonatal ECG activities.Methods ECG was evaluated in 50 neonates with CH aged 17-28 days and 35 healthy neonates in this study.ECG parameters,including heart rate (HR),PR interval (PR),QRS time (QRS),QRS axis in the frontal plane (QRSa),QT time (QT) and corrected QT time (QTC) were analyzed.Chemiluminescent immunoassay was used to measure serum triiodothyronine (FT3),free thyroxin(FT4),total thyrotropin(TT3),total thyroxin(TT4) and thyrotropin(TSH) .Correlation analysis was also made between left ventricular function parameters and serum thyroid hormones levels.Results Serum FT3,FT4,TT3,TT4 levels in CH group were significantly lower than those in normal control group,while serum TSH level in CH group was significantly higher (Pa<0.001).HR in CH group was significantly lower compared with normal control group (P<0.05),which was positively correlated with FT3,FT4 serum levels (Pa<0.05),and negatively correlated with TSH serum level (Pa<0.05).PR and QT in CH group were significantly longer than those in the control group (Pa<0.05).PR was negatively correlated with FT3,FT4, TT4 serum levels (Pa<0.05),and positively correlated with TSH serum levels (Pa<0.05).No statistical differences of QRS,QRSa,and QT were noted between two groups(Pa>0.05).Conclusions CH has predominant effect on pacemaker cells of sinus node in neonates,which may result in changes in autorhythmicity,while some other electrophysiologic effect such as cardiac action potential or atrioventricular conduction have not yet been affected.