(821) Biopsy-Proven Fulminant Myocarditis Requiring Mechanical Circulatory Support Following Third Dose of COVID-19 MRNA Vaccination

INTRODUCTION: Myocarditis has been recognized as a rare complication of coronavirus disease 2019 (COVID-19) messenger RNA (mRNA) vaccinations. The frequency of the event was reported 2-3 cases per million vaccinations. Clinical courses remain variable, ranging from asymptomatic to severe heart failure requires mechanical circulatory supports (MCS). Here we report a case of fulminant myocarditis requiring MCS following COVID-19 mRNA vaccination. CASE REPORT: A 22-year-old male presented to the hospital with chest pain and fever 2 days after receiving the third dose of the COVID-19 mRNA vaccination. Electrocardiography showed tachycardia with ST-segment elevation. Inflammatory and myocardial injury markers were elevated, and echocardiography demonstrated slight left ventricular (LV) dysfunction. He was hospitalized for suspecting acute myocarditis. On the second day of hospitalization, he developed recurrent ventricular fibrillation with cardiogenic shock leading to need for venoarterial extracorporeal membrane oxygenation and intra-aortic balloon pumping. Echocardiography revealed severe LV systolic dysfunction. Catheter examinations showed normal coronary with elevated right and left sided filling pressures and decreased cardiac output. Endomyocardial biopsy (EMB) revealed moderate endomyocardial thickening, mild inflammation, increased interstitial fibrosis and cell infiltration with more macrophages (CD68+) (Figure) (awaiting the results of tenascin-C, angiotensin converting enzyme 2 and severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] spike S protein). No viral genomes including SARS-CoV-2 were detected in the EMB specimens by polymerase chain reaction test. With advanced therapy, he was discharged on the 26th day without any cardiac dysfunction. SUMMARY: Histological evaluation is important for diagnosing myocarditis following COVID-19 vaccination to confirm type of inflammation and the absence of viral genomes.