Publication date: Dec 25, 2024

The effects of myocarditis after mRNA COVID-19 vaccination (mCV) on myocardial tissue, and the association between cardiomyocyte injury and clinical presentation, are not fully understood. We retrospectively registered patients clinically diagnosed with myocarditis after the first or second mCV who underwent endomyocardial biopsy or autopsy from 42 participating centers in Japan. We investigated the histological features and their association with clinical presentation based on cardiomyocyte injury. Forty patients who underwent endomyocardial biopsy were included in the study. Of these, 19 (47. 5%) showed mild lymphocytic infiltration and interstitial edema without cardiomyocyte injury. The remaining 21 (52. 5%) patients showed cardiomyocyte injury accompanied by infiltrating inflammatory cells: 11 with lymphocytic infiltration, 7 with eosinophilic infiltration, and 3 with myocarditis with both lymphocyte and eosinophil infiltration. Compared with patients without cardiomyocyte injury, those with cardiomyocyte injury were clinically characterized by older age, a balanced sex distribution, less frequent chest pain, and a lower left ventricular ejection fraction. Fifteen of 21 (71. 4%) patients with cardiomyocyte injury developed fulminant myocarditis, with 13 (86. 7%) requiring mechanical circulatory support; in contrast, none of those without cardiomyocyte injury developed fulminant myocarditis (P

Semantics

Original Article