P2.L223: Discovering the Unknown: Adolescent with Dilated Cardiomyopathy with Severe Acquired Hypothyroidism

Introduction: Dilated cardiomyopathy (DCM) involves the enlargement and weakening of the heart muscle. It can have genetic, viral, or idiopathic causes. It affects people of various age groups, races, and ethnicities. The incidence rate of DCM in children is approximately 0.57 per 100,000 population.

Case Description: A 16-year-old female presented to the emergency department (ED) with respiratory distress, cough, and vomiting. Her past medical history was remarkable for hyperthyroidism post-ablation with acquired hypothyroidism.
She had multiple ED visits for respiratory distress with worsening fatigue, dizziness, orthopnea, and a syncopal event, prompting a final ED visit. In the ED, she was tachycardic (120 bpm), tachypneic (RR 44 rpm), and low SpO2 of 86% to 94%. Chest x-ray revealed pulmonary edema and cardiomegaly (Pic.1). Blood work showed a lactate of 2.9 mmol/L, high troponin levels at 20.3 mmol/L, and a viral panel positive for adenovirus. Her thyroid values indicated hypothyroidism with a T4 level of 0.2 ng/dL and a TSH level of 128 uIU/mL. She was started on BiPAP and then transferred to the PICU. An echocardiogram showed dilated right and left ventricles, mild to moderate mitral regurgitation, and mild tricuspid regurgitation, with a left ventricular ejection fraction of 15% (Pic.2). An ECG displayed a sinus rhythm at 108 bpm, left atrial dilatation anterolateral T wave inversions, and a possible left ventricular hypertrophy. She was started on Levothyroxine without cardiac improvement. She was transferred for decompensated CHF management and severe left ventricular systolic dysfunction. Genetic testing for DCM was negative.
Following aggressive management without improvement, an Impella 5.5 LVAD was implanted, which was followed by a Bi-caval orthotopic heart transplant. The patient recovered successfully.

Discussion: DCM is the most common phenotypical variant of cardiomyopathies in children and adolescents. It involves reduced contractility, dilatation, and thinning of the left ventricle.
Patients with a history of radiation and Graves' disease may rarely develop radiation-induced DCM. Thyroid hormones affect cardiac function, and hypothyroidism can also cause DCM. Levothyroxine treatment can improve myocardial function, but it was unsatisfactory for our patient. DCM has genetic forms that account for almost half of the cases. DCM shows genetic heterogeneity with around 40 causative genes; not all may have been identified yet. Cardiac transplantation is reserved for severe cases, as in our case.

Conclusion: Due to its multifactorial pathogenesis, diagnosing DCM in adolescents can be challenging. To identify underlying causes, a thorough evaluation of clinical history, laboratory findings, and imaging studies is necessary. Timely initiation of appropriate treatment is essential to prevent disease progression and improve prognosis. A comprehensive and multidisciplinary approach to management is crucial.