Gentle Giant: An Unusual Cause of Heart Block

Abstract

<h3>Introduction</h3> Inflammatory cardiomyopathies can be a diagnostic dilemma. Early management can lead to reduced morbidity and mortality for patients. We describe a rare presentation of an unusual cardiomyopathy. <h3>Case Report</h3> A 58-year-old female presented with a 10-day prodrome of cough, NYHA class III dyspnea, and fatigue with minimal symptoms of orthopnea, paroxysmal nocturnal dyspnea or peripheral edema. She was previously healthy with no cardiac medications. Family history was significant for granulomatosis with polyangiitis. COVID-19 swab was negative. She was symptomatic with transient complete heart block and junctional escape of 20bpm. A temporary transvenous pacemaker was placed. Echocardiogram showed biventricular dysfunction with left ventricular ejection fraction < 30%. Troponin and brain-natriuretic peptide were elevated. Coronary angiogram showed no significant occlusions. CT excluded pulmonary embolism, pneumonia, or adenopathy. She was initiated on heart failure medications but beta blocker was not started given heart block. Six days into admission, her heart failure improved but she developed transient complete heart block without junctional escape. There was no ventricular ectopy. Evaluation for rheumatologic, infectious, and inflammatory causes showed elevated C-reactive protein and antineutrophil cytoplasmic antibodies. The remainder of the workup was negative. Leading diagnoses were idiopathic giant cell myocarditis or cardiac sarcoidosis. An endomyocardial biopsy revealed multinucleated giant cells and myocyte necrosis. She was diagnosed with giant cell myocarditis. Prior to discharge, she had defibrillator insertion and was initiated on prednisone and tacrolimus. Shortly after this time, she returned with critical cardiogenic shock despite intensification of immunosuppressive therapies and was listed for cardiac transplant. <h3>Summary</h3> Giant cell myocarditis (GCM) is a rare and often fatal autoimmune cause of heart failure. Patients frequently present with congestive heart failure, ventricular arrhythmia and a rapid progression of symptoms. In GCM, it is rare to present with atrioventricular conduction delays. Given the crossover in symptoms with sarcoidosis and GCM, diagnosis may be challenging. In this case of an acute presentation of heart failure and complete heart block, endomyocardial biopsy was central to the diagnosis and management of GCM.