Slide 1: A 66 y/o M was found unresponsive and hypothermic inside his home with this EKG. What abnormalities do you see?

Slide 2: 1. Artifact. 2. Sinus bradycardia. 3. First degree AV block. 4. Intra-ventricular conduction delay (IVCD). 5. Prolonged QT.

Slide 3: In a patient with hypothermia and these EKG findings, which labs would you order? Free T4 and thyroid stimulating hormone (TSH). This patient’s free T4 was undetectable and TSH was 40.

Based on this patient’s presentation, EKG findings, and lab abnormalities, what is this diagnosis?

Slide 4: In this patient with: presentation of hypothermia and unresponsiveness, EKG showing sinus bradycardia with first degree AV block, IVCD, and prolonged QTc, and labs showing undetectable free T4 and high TSH…the diagnosis is myxedema coma!

What is myxedema coma? Myxedema coma is an extreme manifestation of hypothyroidism leading to multiple organ abnormalities and deterioration of mental status.

Slide 5: What are the different types of cardiac findings in hypothyroidism?

Electrical. Slowed conduction – bradycardia, first degree AV block, intra-ventricular conduction delay, QT prolongation. Low QRS voltage. T wave inversions.

Myocardial. Decreased contractility, decreased cardiac output, and diastolic dysfunction.

Pericardial. Pericardial effusion (can cause tamponade, though rare) and acute pericarditis.

Coronary. Accelerated atherosclerosis – due to altered lipid metabolism.


  • Wall CR. Myxedema coma: diagnosis and treatment. Am Fam Physician. 2000 Dec 1;62(11):2485-90. PMID 11130234.
  • Baldwin C, Newman JD, Vallejo F, Peck V, Greene LW, Goldberg IJ. Myxedema Heart and Pseudotamponade. J Endocr Soc. 2020 Aug 27;5(1):bvaa125. PMID 33354637.
  • Klein I, Ojamaa K. Thyroid hormone and the cardiovascular system. N Engl J Med. 2001 Feb 15;344(7):501-9. PMID 11172193.
  • Udovcic M, Pena RH, Patham B, Tabatabai L, Kansara A. Hypothyroidism and the Heart. Methodist Debakey Cardiovasc J. 2017 Apr-Jun;13(2):55-59. PMID 28740582.

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