ECG Abnormalities in Hyperthyroidism

The most common ECG changes seen with thyrotoxicosis are:

Other ECG abnormalities include:

Around 50% of patients with thyrotoxicosis will have a resting heart rate > 100 bpm. Atrial fibrillation is seen in up to 20% of patients. Severe thyrotoxicosis (thyroid storm) may present with atrial tachycardias at rates > 200 bpm.

  • The ECG changes in thyrotoxicosis are principally related to increased activity of the sympathetic nervous system and the stimulatory effects of thyroid hormone on the myocardium.
  • Atrial tissue is very sensitive to the effects of thyroid hormone, hence the preponderance of atrial tachydysrhythmias.

Useful Tips
  • Patients with unexplained sinus tachycardia or atrial fibrillation should have their TSH and T4 checked to look for evidence of thyrotoxicosis.
  • Thyrotoxic atrial tachydysrhythmias are treated with intravenous beta-blockers (e.g. titrated IV boluses of propranolol or an esmolol infusion).

ECG Examples
Example 1
ECG Sinus tachycardia 1

Example 2


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Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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