Abstract 15510: Big Heart Problems: A Case of Reversible Nonischemic Cardiomyopathy Due to Severe Hypothyroidism

Abstract

Introduction: Cardiomyopathy is a heterogeneous group of myocardial diseases that can result in mechanical and electrical dysfunction. Thyroid insufficiency can increase the risk of cardiovascular abnormalities through multiple mechanisms including ventricular arrhythmias, hypertension, and heart failure. Case Presentation: Our patient is a 40-year-old Hispanic female with a past medical history of papillary thyroid carcinoma with a right-sided hemithyroidectomy in 2019 who presented to the emergency department with a 1-week history of dyspnea and peripheral edema. She has a family history of sudden cardiac death in her father. She discontinued her levothyroxine 75 mcg once daily dose 6 months ago as she believed this was causing her headaches. Her vital signs were significant for a heart rate of 117 beats per minute and a blood pressure of 185/147 mmHg. Her lab work showed a thyrotropin level of 94.6 uIU/mL, free thyroxine of 0.57 ng/dL, troponin T of 22 ng/L, and proBNP of 2660 pg/mL. A transthoracic echocardiogram (TTE) demonstrated global left ventricular hypokinesis with a left ventricular ejection fraction (LVEF) of 30-35%. Her electrocardiogram (EKG) showed normal sinus rhythm and corrected QTc of 494 ms. She received levothyroxine and furosemide and was discharged with guideline directed medical therapy (GDMT). Her outpatient TTE demonstrated improved LVEF of 40-45% after two months of levothyroxine use and GDMT. Discussion: Hypothyroidism has many cardiometabolic effects that directly impact cardiac function. Impairments in cardiac contractility can result in diastolic heart failure leading to low cardiac output, low heart rate, and low stroke volume. Increased vascular permeability results in protein-rich pericardial and pleural effusions. Myxedema, or non-pitting edema can be seen in long-standing, severe hypothyroidism. An increased QTc interval occurs due to prolonged cardiac action potentials which predispose the heart to ventricular irritability. Treatment with levothyroxine can improve cardiac output and contractility, however this carries increased risk of cardiac arrhythmias and myocardial ischemia. Conclusion: Severe hypothyroidism should be considered in cases of isolated nonischemic cardiomyopathy.