Severe primary hypothyroidism is a rare but reversible cause of acquired long QT syndrome and torsades de pointes that may require temporary chronotropic support or permanent pacing if bradycardia persists.
An 85-year-old lady presented to our institution following multiple episodes of transient loss of consciousness. Her admission ECG revealed a junctional bradycardia with significant QT prolongation. Telemetry captured a torsades de pointes arrhythmia. Possible offending drugs (digoxin and hydroxychloroquine) were stopped and she was given intravenous magnesium and potassium. Despite this, she continued to have runs of torsades. An isoprenaline infusion was commenced to increase her resting heart rate. Her QT interval shortened and she had no further arrhythmia. Investigation into the cause of her bradycardia and prolonged QT revealed profound hypothyroidism. Levothyroxine was commenced but the patient remained bradycardia and required a permanent pacemaker. She had no further arrhythmia and was discharged home safely. This is a very rare case of severe primary hypothyroidism presenting with torsades de pointes.
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Kandan et al. (2012) studied this question.
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