Fulminant myocarditis is an uncommon but severe cardiac manifestation of systemic lupus erythematosus (SLE), which can rapidly progress to heart failure and life-threatening rhythm disturbances. We report the case of a 33-year-old woman with a recent diagnosis of SLE who developed rapidly progressive cardiac involvement leading to cardiogenic shock and complete atrioventricular block. Her condition required intensive care management, including mechanical ventilation and temporary pacing. Following treatment with high-dose corticosteroids and cyclophosphamide, a marked improvement in ventricular function was observed, with the left ventricular ejection fraction increasing from 20% to 48%. Despite this recovery, the conduction abnormality persisted. This case highlights the fulminant presentation of lupus myocarditis, the reversibility of myocardial dysfunction and the potential persistence of conduction system involvement.