Does Subclinical Hypothyroidism Alter the Axis of QRS and P Waves?

Abstract

Aim: What changes subclinical hypothyroidism (SCH) causes on the 12-lead surface electrocardiogram (ECG) has remained elusive. We examined the relationship between subclinical hypothyroidism and cardiac electromechanics, including P wave and QRS axes on ECG and cardiac functions by 2D speckle-tracking echocardiography (2D-STE). Material and Method: This cross-sectional study included 109 SCH patients who presented to the internal disease outpatient clinic between November 10, 2018, and January 30, 2019. ECG, 2D-STE images, and laboratory findings at admission were recorded for all patients. Findings were compared with a sex and age-matched control group of 74 healthy adults. Results: The median age of the patients was 41 (IQR, 34–50) years, and 76.1% were female. QTc interval was significantly longer in the patient group than in the control group.[435 ms (IQR, 421–457) vs. 424 ms (IQR, 412–438), p=0.001]. The remaining ECG features, including P wave and QRS axes, were similar between the patient and control groups. There were no significant differences between the patients and control group regarding laboratory and echocardiography findings, including left ventricle global longitudinal strain. Conclusion: According to our findings, individuals with SCH exhibited no change in myocardial mobility as measured by strain echocardiography. In addition, SCH may not cause significant ECG changes, except that these patients have a longer QTc interval than subjects with euthyroidism.

Keywords

• ECG
• electrocardiogram
• QRS axis
• QTc interval; speckle-tracking echocardiography; subclinical hypothyroidism

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