SUN-588 Myxedema Heart Unveiled - Profound Hypothyroidism With a Large Pericardial Effusion

Abstract S. Mahesh: None. J. Narvaez Intriago: None. S. Bhashini Popuri: None. C.E. Guillen Lopez: None. C. Arima: None. M.L. Ionescu: None. Introduction: While hypothyroidism is a recognized etiology of pericardial effusion, cases presenting with this manifestation are exceedingly uncommon. We report a case of a 36 year old man who presented with lower extremity edema and generalized weakness. Echocardiogram revealed a substantial pericardial effusion and thyroid function testing confirmed marked hypothyroidism. This case reflects the unusual presentation of hypothyroidism with a pericardial effusion. Case Report: A 36 year old man presented to the hospital with 3 weeks of progressive bilateral lower extremity edema and generalized weakness. Vital signs at presentation were significant for bradycardia to 57. Physical exam showed bilateral pretibial pitting edema, dry skin and distant heart sounds. EKG revealed sinus bradycardia and low voltage QRS complexes. Chest radiograph revealed an enlarged cardiac silhouette. Echocardiogram demonstrated a large pericardial effusion with swinging of the heart and right ventricle diastolic collapse. Thyroid function tests showed TSH >46 µIU/mL, Free T4 <0.5 ng/dL and T3 0.20 ng/mL. He underwent pericardiocentesis with temporary pericardial drain placement, with drainage of clear yellow pericardial fluid. Given his thyroid function tests, Endocrinology was consulted, and he was started on Liothyronine and IV Levothyroxine. Free T4 and T3 levels were monitored daily. Levothyroxine was switched to an oral formulation once Free T4 levels were detectable in the blood. Discussion: Severe hypothyroidism can cause 'myxedema heart’, which presents with relative sinus bradycardia, low voltage QRS complexes and pericardial effusions. Characteristically, myxedema heart presents as 'pseudo-tamponade' - echocardiographic findings consistent with cardiac tamponade, with stable clinical hemodynamics (such as in our patient). Rarely, large pericardial effusions can cause hemodynamic compromise. Accumulation of pericardial fluid may be explained by increased capillary permeability and decreased lymphatic drainage caused by hypothyroidism. Per the AACE/ATA guidelines, severe hypothyroidism should be medically managed with thyroid hormone replacement with levothyroxine. While evidence does not support the routine use of combinations of Levothyroxine and L-triiodothyronine (T3), it is sometimes used in management of severe hypothyroidism. Conclusion: Pericardial effusion with relative bradycardia is the most frequent finding in myxedema heart. No specific guidelines exist to evaluate and manage pericardial effusions associated with severe hypothyroidism. Effusions are usually medically managed with thyroid hormone replacement with Levothyroxine. Dramatic response to thyroid hormone supplementation is usually seen. Pericardiocentesis is beneficial when the diagnosis is in doubt or in case of cardiac tamponade. Sunday, June 2, 2024