Repetitive monomorphic ventricular tachycardia as a manifestation of suboptimally treated thyrotoxicosis.

Monomorphic ventricular tachycardia (VT) is a unique manifestation of hyperthyroidism. We present the case of a 41-year-old male with a history of hyperthyroidism presenting with palpitations secondary to non-sustained episodes of monomorphic VT. Cardiac arrhythmias due to thyrotoxicosis are perpetually supraventricular in origin. Monomorphic VT in the setting of thyrotoxicosis in the absence of structural heart disease is exceedingly rare. After starting propranolol and increasing the dose of methimazole, the patient had no further episodes of VT. It is important to recognize repetitive monomorphic VT as an understated but important manifestation of thyrotoxicosis. Propranolol is associated with an excellent response in these patients and anti-thyroid medications such as methimazole effectively reverse thyrotoxicity.