Am Heart Hosp J. 2010;8(2):113–114


Lozenge Reference


Case Report


Repetitive Monomorphic Ventricular Tachycardia as a Manifestation of Suboptimally Treated Thyrotoxicosis


Preeti A Chandra, MD, Ajay Vallakati, MD, MPH, Abhinav B Chandra, MD, Manali Pednekar, MD and Joydeep Ghosh, MD


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.


41-year-old male with a six-year history of hyperthyroidism presented with palpitations and dizziness. He had been experiencing the symptoms for the past two months, had lost 37 pounds in weight in the previous 10 weeks, and was heat intolerant. He was taking methimazole 5mg daily. The patient denied chest pain, shortness of breath, and syncope.


A


Physical examination revealed thyroid enlargement with no nodules or bruit, fine resting tremors, and lid lag. The patient’s serum electrolyte and magnesium levels were normal. His thyroid-stimulating hormone (TSH) level was zero, free thyroxine (T4) level was 4.99, free triiodothyronine (T3) level was 10.66, and total T4 level was 15. Cardiac enzyme levels were normal. The patient was in normal sinus rhythm at 64 beats per minute but telemetry revealed that he was having multiple non-sustained episodes of wide QRS tachycardia at 300 beats per minute (see Figure 1). A recent cardiac work-up including nuclear stress test, gated single photon emission computed tomography (SPECT) study, and echocardiogram had demonstrated normal left ventricular size, wall motion, myocardial thickness with normal myocardial perfusion,


and an ejection fraction (EF) of 68%. Electrophysiologic evaluation gave a diagnosis of monomorphic ventricular tachycardia (VT).


The patient was started on propranolol 30mg every six hours and his methimazole dose was increased to 10mg every eight hours. It was also planned to implement radioactive thyroid ablation when he reached a euthyroid state. The patient had no further VT episodes after initiation of propranolol. He was monitored continuously by telemetry for one week, after which he was discharged uneventfully. Follow-up continued in the outpatient clinic.


Discussion


Thyrotoxicosis—often diagnosed in an outpatient setting— commonly manifests as weakness, weight loss, and palpitations. Other common symptoms include irritability and heat intolerance.1


Atrial fibrillation is the most common


cardiac manifestation of thyrotoxicosis, and occurs in up to 15% of hyperthyroid patients.2


T3 decreases systemic


vascular resistance and increases resting heart rate, left ventricular contractility, blood volume, and cardiac output and thereby is responsible for most of the cardiac


• Maimonides Medical Center, Brooklyn, NY • Correspondence: Preeti A Chandra, MD, 864 49th Street, Apt C-18, Brooklyn, NY 11220. E: drpreetichandra@yahoo.com


Winter 2010 Repetitive Monomorphic Ventricular Tachycardia as a Manifestation of Suboptimally Treated Thyrotoxicosis 113


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