Sex-related differences in characteristics and outcome of patients with acute myocarditis: insights from the Prospective MyocarditIRM Study

Background Acute myocarditis (AM) occurs substantially more frequently in males. In contrast, females tend to present at older ages, and may experience higher risks of complications although results are conflicting (1, 2). Data on sex-specific prospective course of AM are lacking. This study aimed to fill this gap by comparing clinical features, imaging findings, and in-hospital outcomes between men and women, and describing their distinct phenotypes. Methods MyocarditIRM is a multicenter prospective observational study of patients with cardiac magnetic resonance (CMR)-proven AM (3). The main non-inclusion criterion was initial admission to the intensive care unit. Patients were divided into male and female groups. Clinical, biological, electrocardiogram (ECG), and imaging data as well as in-hospital events were systematically collected. CMR features were analyzed centrally by the CoreLab (IHU-ICAN, Paris, 2024/109689.1). In-hospital complications were analyzed by sex using logistic regression adjusted for age and initial severity. Results A total of 788 patients with AM were included (647 men, 141 women). Women were older (34 vs. 30 y, p=0.009) and had higher rates of hypertension and immunological disorders. At presentation, women more frequently presented with dyspnea, whereas men more often had chest pain and infectious prodromes. On CMR, women had higher LVEF and fewer segments with late gadolinium enhancement. Biologically, women had lower troponin and C-reactive protein at admission. Coronary imaging and endomyocardial biopsy were performed in a similar proportion of women and men. The proportion of patients meeting criteria for initial severity – including LVEF <50%, severe arrhythmia, high-degree AV block, or cardiogenic shock – was not statistically different in women and men (18% vs. 12%; p=0.071), despite a trend towards more complicated AM in women. STEMI-like presentations – defined as a chest pain with ST-elevation on admission ECG, without initial severity criteria or in-hospital complications – occurred in 40% overall, more often in men (44% vs. 24%, p<0.001). In logistic regression adjusted for age and initial severity, sex was not associated with in-hospital complications – including death, LVEF <40%, sustained arrhythmia, cardiogenic shock, or need for mechanical or device support – which occurred in 10% of women and 7% of men. Conclusion In the prospective MyocarditIRM study, AM predominantly affected men, whereas women were older, had more comorbidities, were less likely to present with STEMI-like symptoms, and had fewer affected segments on CMR; however, initial severity and in-hospital complications were not statistically between sexes. These sex-specific analyses may have implications for diagnosis and therapeutic strategies.