Utility of cardiac magnetic resonance imaging in diagnosing eosinophilic myocarditis in a patient with hypereosinophilic syndrome. (QF_FR_133)

A 74-year-old male with a significant history of hypertension, chronic kidney disease stage III-b and atrial flutter presented with one month history of with worsening heart failure symptoms. He reported acute onset dyspnea on exertion and bilateral lower extremity edema. His peripheral eosinophil counts had been elevated since 2006, peaking recently at 1500-3000 cells/µL leading to a diagnosis of hypereosinophilic syndrome.

On physical examination, the patient was well-appearing and in no acute distress. Cardiovascular examination showed elevated jugular venous pressure to the mandible with prominent V-waves.

Diagnostic Techniques and Their Most Important Findings:

Laboratory investigations revealed thrombocytopenia (133,000 uL; reference: 150,000-400,000 uL), normal leukocyte count (6210 uL; reference: 3,700-10,200 uL) and eosinophilia (2527 uL; reference: 0-400 uL). Serum IgE and IgM levels were elevated (2369; reference range < 114 kU/l) and (3,180; reference range: 40-230 kU/l), respectively. Rheumatoid factor, ANA, ANCAs and troponin I (0.075 ng/dl; reference: 0-0.4 ng/mL) were negative. Brain natriuretic peptide (BNP) was 1,891 pg/ml.

Chest X-RAY showed trace pleural effusions bilaterally. Transthoracic echocardiogram revealed a mildly decreased left ventricular ejection fraction (LVEF) of 50%, severely dilated right atrium, and severe tricuspid valve regurgitation. Notably, there were echodensities concerning for thrombi in the right and left ventricular apex, prompting further imaging.

Cardiac magnetic resonance (CMR) revealed asymmetrical left ventricular hypertrophy with pronounced apical thickening, biventricular thrombi, scattered subepicardial, mid-myocardial and subendocardial late gadolinium enhancement involving all myocardial segments of the left ventricle and right ventricular apex. The left ventricular thrombus measured 2.4x1.5cm, and the right ventricular thrombus measured 2.8x1.1cm. Additionally, the patient exhibited severe tricuspid regurgitation secondary to tricuspid annular dilatation, with a regurgitant volume of 66 mL/beat and a regurgitant fraction of 55%. The patient declined to undergo a confirmatory endomyocardial biopsy.

Given the CMR findings and established diagnosis of hypereosinophilic syndrome, the patient was diagnosed with eosinophilic myocarditis. The patient was started on dexamethasone for eosinophilic myocarditis and rivaroxaban for biventricular thrombi. Unfortunately, the patient passed away six months later due to an episode of pneumonia leading to sepsis and significant organ dysfunction.

Learning Points from this Case:

Hypereosinophilic syndrome (HES) is characterized by persistent marked eosinophilia ( >1500 eosinophils/mm(3)), the absence of a primary cause of eosinophilia, and evidence of eosinophil-mediated end organ damage.¹ Cardiac involvement in HES can manifest as myocarditis, endomyocardial fibrosis, and intracardiac thrombi.²

CMR is instrumental in diagnosing and assessing the extent of myocardial involvement in eosinophilic myocarditis. Late gadolinium enhancement sequences are particularly useful for identifying areas of myocardial damage and fibrosis, guiding further management and prognostication. ³ In CMR, eosinophilic myocarditis is characterized by extensive myocardial hyperintensity on T-2 weighted imaging with subendocardial delayed enhancement.⁴ Mesocardial and epicardial delayed enhancement have also been reported.^5\