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
Sinus tachycardia

Example 2

Related Topics


  • Slovis C, Jenkins R. ABC of clinical electrocardiography: Conditions not primarily affecting the heart. BMJ. 2002 Jun 1;324(7349):1320-3. [PMC1123277]

LITFL Further Reading

Advanced Reading




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

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