Differential reversibility in heart failure due to hypothyroidism: A series of contrasting cases with review of literature

Introduction: Ranking third as a leading cause of heart failure in the United States, dilated cardiomyopathy (DCMP) affects 5 in 100,00 adults with an eight-year mortality rate between 7080%. In the setting of hypothyroidism, DCMP is unique due to its potential reversibility with medical therapy. Thyroid hormone affects cardiac physiology and intracellular calcium regulation via SERCA2 and phospholamban, with concentrations of phospholamban most numerous in the ventricles. Administration of thyroid hormone can restore contractile function. However, the relationship between disease timeline and reversibility in DCMP due to hypothyroidism has not been previously described. Case Series: A 65-year-old Caucasian male presented with new onset severe dyspnea and fatigue. Thyroid-stimulating hormone was markedly elevated. Following levothyroxine therapy, his dilated cardiomyopathy reversed and returned to normal within six months. LVEF improved from 1545% with decreased chamber dilation. A 60-year-old Caucasian female presented minimally responsive in overt heart failure due to myxedema coma. History revealed chronically uncontrolled hypothyroidism. TSH was significantly elevated. Following prolonged hospitalization and intravenous levothyroxine therapy, her clinical status began to reverse. LVEF improved from 1025%, with decreased chamber dilation. Conclusion: Once the underlying mechanism of heart failure was addressed, the cases displayed varying recovery of contractility following thyroid hormone replacement. This may suggest that with longer duration of uncontrolled disease and consequent cardiac structural remodeling, the reversibility diminishes into irreversibility. These cases underscore the need to identify and treat early any contributing hypothyroidism in the setting of new onset dilated cardiomyopathy, as reversibility may be at stake.