Study Of The Relations Between Thyroxin Level And Electrocardiogram In Hypothyroidism

Objective To assess the changes of electrocardiographic (ECG) manifestations in hypothyroidism, as well as its correlation with thyroid hormones serum levels and the influence on patient's ECG activities. Methods ECG was evaluated in 144 hypothyroidism patient and 163 healty person(control group) in this study. ECG parameters, including heart rate (HR), PR interval(PR),QRS time (QRS), QT time (QT) , ST segment depression and T waves were analyzed.Chemilumines-cent immunoassay was used total thyrotropin(TT₃), total thyroxin(TT₄) and thyrotropin(TSH). Correlation analysis was also made between leftventricular function parameters and serum thyroid hormones levels. Results the abnormality of electrocardiogram in Hypoth- yroidism were higher than control group (X²=34.557, p=0.000). Electrocardiogram in Hypothyroidism would be abnormal when the decrease of TSH (t=2.872, p <0.01), and the increase of T₄ ,T₃ (P<0. 01,p <0.05). HR in hypothyroidism group was significantly lower compared with normal control group, PR, QRS and QT in hypothyroidism group were significantly longer than those in the control group (P<0. 01).HR positively correlated with TSH, T₃ PR, QRS and QT was negatively correlated with T₃, T₄, but was positively with TSH . ST segment depression and T waves were negatively correlated with TSH, but was positively with T₃, T₄ (P <0. 05),t has significance in statistics. Conclusions the abnormality of electrocardiogram would be seen as Hypothyroidism group 54.2% and control group 14.7%, also as the decrease of TSH and the increase of T₄,T₃. Hypothyroidism has predominant effect on pacemaker cells of sinus node in patient, which may result in changes in autorhythmicity and Myocardial ischemia.