12393 Myxedema Presenting With Impending Cardiac Tamponade : A Case Report

Abstract Disclosure: A. Hoskote: None. V. Gupta: None. J. Seidenberg: None. The widespread availability of thyroid stimulating hormone (TSH) assays, routine screening and affordable replacement therapy has resulted in decreased prevalence of complications of untreated hypothyroidism. “Myxedema heart” is a rare syndrome that results in bradycardia, cardiomyopathy and pericardial effusion. We present a rare case of cardiac tamponade due to myxedema in a patient with unidentified hypothyroidism. A 49-year-old male was brought to the ER by his family for several weeks of cognitive slowing, weakness and inappropriate behavior involving defecating on himself eating old food and barricading in his room. The patient denied past medical or psychiatric history, medication use or recent physician evaluation. On exam he had macroglossia, was disheveled, forgetful but alert with slow speech, ataxia and muscle wasting. He was afebrile and hemodynamically stable. EKG showed sinus bradycardia. Labs were notable for sodium 133, hemoglobin 8.8g/dL and TSH was incidentally >100U. Levothyroxine was begun. The next day, he was noted to have increased lethargy, bradycardia and hypoglycemia and was transferred to the intensive care unit with concern for myxedema coma. Free T4 was <0.3 ng/dL (0.6-1.6) and free T3 was 1.6pg/mL (2.5-3.9). An echocardiogram revealed a large circumferential pericardial effusion with right atrial and ventricular collapse with tamponade. Treatment with 5 mcg liothyronine, intravenous levothyroxine and stress dose hydrocortisone was begun. A pericardial drain was placed, draining 980mL of sanguineous fluid. After clamping trials, the drain was removed 48 hours later. Labs revealed thyroglobulin <0.1ng/mL (1.6-50), thyroid peroxidase (TPO) antibody 574 IU/mL (<9), thyroglobulin antibody >2500 (<4) and thyroid ultrasound showed a normal sized thyroid gland with heterogenous echogenicity confirming a diagnosis of Hashimoto’s thyroiditis. Serial echocardiograms during the admission and a follow-up two months later showed a stable posterior effusion with no recurrence of the anterior pericardial effusion. Gradually mentation, hemodynamics and electrolyte derangements improved, and he was discharged on oral levothyroxine. TSH values showed sequential improvement to 48U in 15 days and to 11U in 2 months. Myxedema is a manifestation of severe hypothyroidism. The pericardium, a collagen-rich structure, is susceptible to myxedematous infiltration, leading to pericardial effusion. While small pericardial effusions are common with chronic hypothyroidism, a large pericardial effusion with tamponade is a rare life-threatening complication that requires prompt recognition and management. Clinicians must promptly identify myxedema and replace thyroid hormone to prevent progression of pericardial effusion to tamponade, maintaining especially high suspicion in those at risk of poor access to healthcare or inadequate health literacy. Presentation: 6/3/2024