The Cleveland Clinic experience of eosinophilic myocarditis in the setting of hypereosinophilic syndrome: demographics, cardiac imaging, and outcomes.

Background: Hypereosinophilic syndrome (HES) represents a group of disorders with eosinophil-mediated end-organ damage. Eosinophilic myocarditis (EM) represents cardiac involvement in HES. Data are limited regarding this rare condition. To better understand contemporary clinical characteristics of EM in HES, we reviewed demographics, cardiac imaging, and outcomes of this condition at our center.

Methods: We performed a cross-sectional study of all patients aged >18 years with diagnosis of EM in HES at our center between September 1986 and January 2023. Relevant clinical data, including clinical presentation, medical history, medication use, comorbidities, imaging findings, and outcomes, were collected and analyzed.

Results: Of 1,664 patients identified with hypereosinophilia (HE), 36 cases of clinically diagnosed HES were identified. Of the 36 patients diagnosed with HES, 11 patients (30.6%) were diagnosed with EM. Of these, six patients underwent endomyocardial biopsy (EMB). The mean age was 57±12 years and 63.6% were female. Asthma was the most common comorbidity (54.5%). Patients with EM had significantly more dyspnea (63.6%), fatigue (54.5%), and neuropathy (36.4%) compared to those without cardiac involvement. Echocardiography was performed in all patients and cardiac magnetic resonance (CMR) imaging was performed in eight patients. Left ventricular (LV) thrombus was detected more frequently by CMR (5/8, 62.5%) compared to echocardiography (3/10, 30%). Subendocardial pattern of late gadolinium enhancement (LGE) was observed in the majority of patients on CMR (6/7, 85.7%). Steroids were utilized in 90.9% of cases, and aspirin in all patients. Compared to HES patients without cardiac involvement, thromboembolic events occurred significantly more frequently (63.6% vs. 24.0%, P=0.02).

Conclusions: In a 37-year cohort of HES-associated EM, echocardiography was the first-line imaging modality, while CMR was an essential but still under-utilized imaging modality. Patients with EM had significantly more thromboembolic events compared to HES without cardiac involvement.