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Prolonged ventricular repolarization measured by corrected QT interval (QTc) in subclinical hyperthyroidism
M Owecki1, A Michalak, E Nikisch
1Department of Endocrinology, Metabolism and Internal Medicine, Poznan University of Medical Sciences, Poznań, Poland. mowecki@amp.edu.pl
Hormone and Metabolic Research = Hormon- Und Stoffwechselforschung = Hormones Et Metabolisme
|February 16, 2006
Summary
Subclinical hyperthyroidism prolongs corrected QT intervals (QTc), a measure of ventricular repolarization. This finding suggests potential cardiac risks associated with milder thyroid dysfunction.
Area of Science:
- Cardiology
- Endocrinology
- Electrophysiology
Background:
- Overt thyroid dysfunction significantly impacts cardiac function and ECG.
- The effects of subclinical hyperthyroidism on the circulatory system, particularly ventricular repolarization, remain under investigation.
- Prolonged corrected QT interval (QTc) is linked to increased arrhythmia risk and cardiac mortality.
Purpose of the Study:
- To investigate the influence of subclinical hyperthyroidism on ventricular repolarization, assessed by corrected QT interval (QTc).
- To compare QTc intervals in individuals with subclinical hyperthyroidism versus healthy controls.
Main Methods:
- A case-control study involving 32 patients with subclinical hyperthyroidism and 39 healthy controls.
- Standard 12-lead electrocardiogram was used to measure corrected QT intervals (QTc).
- Heart rate and free thyroxin concentrations were also analyzed.
Main Results:
- Patients with subclinical hyperthyroidism exhibited a significantly higher heart rate compared to controls (80.3 bpm vs. 73.7 bpm, p < 0.05).
- The mean corrected QT interval (QTc) was significantly longer in the subclinical hyperthyroidism group (0.434 s) than in the control group (0.414 s, p < 0.001).
- No significant correlation was found between QTc intervals and free thyroxin concentrations (p = 0.5084).
Conclusions:
- Subclinical hyperthyroidism is associated with significantly prolonged corrected QT intervals.
- These findings suggest that even subclinical thyroid dysfunction may affect cardiac repolarization.