Prolonged ventricular fibrillation treated with nifekalant in fulminant myocarditis following late-onset coronavirus disease 2019.

Fulminant myocarditis (FM) is a life-threatening inflammatory cardiac disease that can rapidly progress to cardiogenic shock or fatal arrhythmias. Delayed-onset FM following coronavirus disease 2019 (COVID-19) infection is rare and cases complicated by sustained ventricular fibrillation (VF) are exceptional.A previously healthy man in his late teens developed dyspnoea and complete atrioventricular block after COVID-19 infection. Echocardiography revealed a left ventricular ejection fraction of 30%. Despite veno-arterial extracorporeal membrane oxygenation and Impella CP support, he developed persistent VF lasting for five days, refractory to amiodarone and repeated defibrillation. Continuous intravenous infusion of nifekalant hydrochloride terminated VF and converted to sinus rhythm. Endomyocardial biopsy demonstrated CD68+ macrophage-predominant inflammation, consistent with COVID-19-associated myocarditis.This case suggests that nifekalant may be a valuable therapeutic option for managing life-threatening ventricular arrhythmias while preserving myocardial contractility in FM following COVID-19 infection.