The following ECG findings may be observed in patients with hypothyroidism

  Sinus bradycardia

  Low voltage

  Prolongation of the PR interval

  Bundle branch blocks

  Flattening or inversion of the T wave

  Ventricular premature contractions (VPS)

  Sustained or non-sustained attacks of ventricular tachycardia (VT)

  Prolongation of the QT interval

  Increased dispersion of the QT interval

  Torsades de pointes




References

  BMJ 2002;324:1320-3.

  Am J Med Sci 2006;331:154-6.





ECG 1. The ECG above is from a 53 years-old hypothyroid woman with a TSH level of 18.
There is widespread
T wave flattening .

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ECG 2a. The ECG above was recorded from a 44 years-old man with mitral stenosis.
The rhythm is atrial fibrillation with a high ventricular rate.

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ECG 2b. The ECG above belongs to the same man. It was recorded several months after the ECG 2a.
Now he has hypothyroidism and the TSH level is > 100 mIU/mL. This time, the rhythm is atrial fibrillation with a very low
ventricular rate. He is not taking beta blocker or calcium channel blocker.

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ECG 3. Ventricular bigeminal rhythm in the Holter recording of a 53 years-old woman with hypothyroidism.
Her TSH level is 18 mIU/mL.

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ECG 4a. The ECG above belongs to a 31 years-old woman with no apparent heart disease. She does not complain of any cardiac
symptoms. She was recently diagnosed as hypothyroidism (her TSH level is 43 mIU/mL). After recording of the above ECG,
she was referred to a cardiologist. Nonspecific T wave abnormality is seen in almost all leads.

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ECG 4b. The ECG above belongs to the same woman and was recorded one day after the ECG 4a. T wave flattening is seen in
almost all leads. This is a frequent ECG finding in patients with hypothyroidism. Absence of cardiac symptoms, the patient's
young age and failure to observe dynamic ECG changes (from ECG 4a to ECG 4b) further support the absence of coronary
artery disease.

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