Abstract 14091: Severe Hypothyroidism Revealing Hidden Tracts

Discussion: Atrioventricular reciprocating tachycardia (AVRT) is a type of Supraventricular tachycardia (SVT) caused by an accessory pathway can result in symptomatic and also life-threatening arrhythmias. Supraventricular tachycardias are less commonly seen in hypothyroidism than hyperthyroidism. We present a case of a 41 year old gentleman who presented with chest pain and SVT was found to have severe hypothyroidism with pre-excitation pattern on his EKG. Case: 41-year-old Caucasian gentleman with history of untreated Hashimoto’s thyroiditis presented with palpitations and acute onset left-sided chest pain. His symptoms were aggravated with movement and improved with rest. When EMS found him, his vitals were significant for tachycardia with a heart rate (HR) of 200 beats per minute (bpm). EKG showed supraventricular tachycardia. Vagal maneuvers were attempted followed by adenosine. This resulted in conversion to sinus rhythm and improvement in HR to 88 bpm. His chest pain completely resolved. He was then brought to the emergency room where he had normal vitals. Examination revealed thyroid gland was palpable and noted to be diffusely enlarged. Laboratory data was significant for an elevated thyroid-stimulating hormone (TSH) of 373 mIU/ml and undetectable free thyroxine (fT4) levels. His creatinine kinase (CK) was high at 16260, and troponin was elevated at 0.220 ng/ml (reference:<0.04 ng/ml). TPO antibodies were >600 IU/ml. EKG demonstrated sinus rhythm with pre-excitation and incomplete left bundle-branch block. He had normal chest x-ray. An echocardiogram showed an ejection fraction of 55% with mild LV diastolic dysfunction. He later underwent a stress myocardial perfusion scan which showed no definite evidence of inducible ischemia. Follow up: He was started on thyroxine replacement therapy. He is due for an EP study to evaluate for an accessory pathway causing pre-excitation with repolarization pattern on his ECG. Conclusion: This case suggests that severe hypothyroidism can also cause supraventricular tachycardias (SVT) by metabolic and conduction derangements revealing concealed bypass tracts in patients with accessory pathways. In most cases these arrhythmias are reversible once the underlying thyroid disorder is treated.