A case of lymphocytic myocarditis in a patient treated with an immune checkpoint inhibitor, a recent class of chemotherapy agents.

Chemotherapy-associated cardiotoxicity is a common adverse event. Immune checkpoint inhibitors (ICI) - a new class of monoclonal antibodies - have revolutionized the management of various diseases. Their use is expected to increase in the near future and their cardiac side effects have been increasingly recognized. CLINICAL CASE: We describe a case of a 67-year-old female patient with urothelial carcinoma undergoing treatment with pembrolizumab who presented to the emergency department with progressive fatigue, retrosternal pain and palpitations for three days. On admission she was diagnosed with acute heart failure (HF). The electrocardiogram revealed a right bundle branch block and ventricular bigeminy. Blood tests showed elevated troponin I, while transthoracic echocardiography revealed severe left ventricular dysfunction. Coronary angiography excluded coronary artery disease. Cardiac magnetic resonance revealed moderate left ventricular dysfunction and late gadolinium enhancement typical of myocarditis. Endomyocardial biopsy confirmed the diagnosis of lymphocytic myocarditis. In the first 48h of hospitalization, she developed transient complete AV block. Corticoid and HF therapy were initiated, leading to symptom improvement and disappearance of the rhythm disturbances. She was discharged on the 12th day, maintaining moderate LV dysfunction, which improved only mildly at a subsequent outpatient assessment. She died suddenly 35 days after discharge. CONCLUSION: Lymphocytic myocarditis is a serious cardiac side effect of ICI therapy. Pembrolizumab is increasingly used, so it is important to be aware of its effects, in order to perform an early diagnosis and provide adequate treatment. Corticosteroid therapy seems to be crucial in preventing disease progression and enabling ventricular remodeling.