Abstract 15666: Comprehensive Biopsy and Clinical Features In Coronavirus Disease 2019 Vaccine-Associated Myocarditis - From Nationwide Survey COMBAT Study in Japan -

Abstract

Introduction: Few studies have reported on myocardial tissue findings of coronavirus disease 2019 (COVID-19) vaccine-associated myocarditis (CVAM). This study aimed to investigate the clinical and histopathological features of patients with CVAM. Methods: This is a multicenter and retrospective cohort study (COMBAT study) of patients who were clinically diagnosed with CVAM and underwent endomyocardial biopsy in 42 participating centers in Japan. The inclusion criteria were the following; 1. Occurrence of clinical symptoms within 30 days after getting the first or second dose of the COVID-19 vaccine between February 2021 and March 2022. 2. The exclusion of acute coronary syndrome using coronary angiography. 3. Abnormality of laboratory tests. Fulminant myocarditis (FM) was defined as catecholamine or mechanical support use during hospitalization. Results: A total of 44 patients were included. Fifteen of 44 (34%) patients were clinically diagnosed with FM. FM patients were older and showed fewer ratio of males than non-FM. Also, FM patients showed significantly a longer duration from vaccination to the occurrence of symptoms and less frequency of chest pain than non-FM (Table).In hematoxylin-eosin (HE) stained samples, 28 of 44 (64%) patients were histologically diagnosed with acute myocarditis. Among them, 24 patients were diagnosed with lymphocytic myocarditis (LM) and 4 with eosinophilic myocarditis (EM). In HE stained samples, 5 of 24 (21%) LM patients visually showed a high ratio of eosinophils compared to the common type of LM. The 5 LM patients had a significantly larger number of eosinophils using by immunohistochemistry of eosinophilic cationic protein and a higher ratio of eosinophils to CD3 than the common type of LM (Figure). Conclusions: In patients with CVAM, there may be a difference in clinical features between FM and non-FM patients. Also, a relatively larger number of eosinophils in the myocardium could be infiltrated in patients with CVAM.