Eosinophilic myocarditis: systematic review

In clinical practice, patients with eosinophilic myocarditis (EM) may forgo the gold standard diagnostic procedure, endomyocardial biopsy (EMB), although it is highly recommended in guidelines. This systematic review aims to summarise current approaches in diagnosing and treating EM with a particular emphasis on the utilisation and value of alternative diagnostic methods.

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, we searched MEDLINE and EMBASE for all peer-reviewed articles using the keywords "eosinophilic myocarditis" from their inception to 10 September 2022.

We included 239 articles, including 8 observational studies and 274 cases, in this review. The median patient age was 45 years. Initial presentations were non-specific, including dyspnoea (50.0%) and chest pain (39.4%). The aetiologies of EM were variable with the most common being idiopathic (28.8%) and eosinophilic granulomatosis polyangiitis (19.3%); others included drug-induced (13.1%) and hypereosinophilic syndrome (12.8%). 82.4% received an EM diagnosis by EMB while 17.6% were diagnosed based on clinical reasoning and cardiac MRI (CMR). CMR-diagnosed patients exhibited a better risk profile at diagnosis, particularly higher left ventricular ejection fraction and less need for inotropic or mechanical circulatory supports. Glucocorticoids were the primary treatment with variability in dosages and regimens.

EMB is the mainstay for diagnostic testing for EM. CMR is potentially helpful for screening in appropriate clinical scenarios. Regarding treatment, there is no consensus regarding the optimal dosage of corticosteroids. Large clinical trials are warranted to further explore the utility of CMR in the diagnosis of EM and steroid regimen in treating EM.