The ECG in Hypothyroidism - Life in the FastLane ECG library

Severe hypothyroidism (myxoedema) causes a triad of:

Other ECG changes that may be seen include:

ECG changes may be secondary to:

Myxoedematous deposits of gelatinous connective tissue within the myocardium.
Decreased activity of the sympathetic nervous system
Effects on the myocardium of reduced levels of thyroxine (i.e. reduced inotropy/chronotropy)

Example 1

Myxoedema coma

This is the admission ECG of a 79-year old man who was referred to ICU with coma, hypothermia, severe bradycardia and hypotension refractory to inotropes.
TSH was markedly elevated with an undetectable T4.
The ECG shows marked bradycardia (30 bpm) with low QRS voltages (esp. in the limb leads) and widespread T-wave inversions, typical of severe myxoedema.

Example 2 –

Myxoedema coma (after treatment)

An ECG of the same patient shortly after initiation of thyroid replacement with intravenous T3 and T4.
The heart rate has normalised and the T-wave inversion has corrected.
Low voltage in the limb leads persists and is likely due to myxoedematous infiltration of the myocardium.

Example 3

Myxoedema

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