The Effects of L-thyroxine Treatment on QT Dispersion in Primary Hypothyroidism.
10.3346/jkms.2007.22.1.114
- Author:
Kyoung Hee KWEON
1
;
Byoung Hyun PARK
;
Chung Gu CHO
Author Information
1. Department of Internal Medicine, School of Medicine, Wonkwang University, Wonkwang Medical Science Research Center, Iksan, Korea. parkbhmd@wonkwang.ac.kr
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
Hypothyroidism;
Thyroxine;
Electrocardiography
- MeSH:
Thyroxine/*therapeutic use;
Middle Aged;
Male;
Hypothyroidism/*drug therapy/physiopathology;
Humans;
Female;
Electrocardiography/*drug effects;
Adult
- From:Journal of Korean Medical Science
2007;22(1):114-116
- CountryRepublic of Korea
- Language:English
-
Abstract:
Hypothyroidism has various cardiovascular manifestation and exhibits electrocardiographic change. The QT dispersion on surface ECG reflects regional variations in myocardial repolarization. The effect of L-thyroxine treatment on ECG parameters, such as QT dispersion, in patients with primary hypothyroidism were investigated. This study involved 18 patients (3 men, 15 women, ages: 48+/-18 yr) with primary hypothyroidism. All patients were checked with a standard 12-lead ECG before and after L-thyroxine treatment. Various ECG parameters were then measured twice. The mean L-thyroxine treatment duration was 22+/-2.7 months. The mean thyroid-stimulating hormone levels of patients before and after therapy were 40.2+/-29.8 microU/mL, 3.6+/-4.6 microU/mL (p<0.001) and free-T4 levels were 0.44+/-0.38 ng/dL, 1.51+/-0.39 ng/dL (p<0.001). After L-thyroxine treatment, QT interval (395+/-42 vs. 380+/-24 msec, p<0.05), QTc interval (434+/-32 vs. 417+/-23 msec, p<0.05), QT dispersion (45+/-23 vs. 30+/-13 msec, p=0.008), QTc dispersion (49+/-23 vs. 32+/-14 msec, p=0.005) significantly decreased. There were no significant changes in the PR and RR intervals, as well as the QRS duration. Our findings suggest that the thyroid hormone affects ventricular inhomogenicity, and that L-thyroxine replacement therapy may reduce malignant ventricular arrhythmia and sudden cardiac death in primary hypothyroidism.
