Fluoropyrimidine Cardiotoxicity With Overlapping Vasospastic and Pericardial Features

BACKGROUND: Fluoropyrimidines are widely used in gastrointestinal malignancies but may produce cardiotoxicity, most commonly coronary vasospasm and rarely inflammatory pericardial involvement. CASE SUMMARY: A 57-year-old man with HER2-positive gastric cancer receiving FOLFOX-6M (leucovorin calcium-FOLinic acid, Fluorouracil and OXaliplatin) plus trastuzumab developed severe chest pain during a 5-fluorouracil (5-FU) infusion. The initial electrocardiogram showed T-wave abnormalities and marked QTc prolongation, whereas cardiac biomarkers remained negative. Echocardiography and coronary computed tomography angiography were normal. Fourteen hours later, new concave ST-segment elevation appeared. Cardiac magnetic resonance demonstrated pericardial hyperintensity and enhancement suggestive of inflammatory involvement, without myocardial necrosis. Symptoms resolved after drug discontinuation and colchicine therapy. DISCUSSION: This case illustrates the diagnostic complexity of 5-FU cardiotoxicity, in which vasospastic, electrical, and possible inflammatory manifestations may overlap or evolve sequentially. TAKE-HOME MESSAGE: 5-FU cardiotoxicity may present late and exhibit multifaceted manifestations and requires a multidisciplinary approach to balance oncologic efficacy with cardiovascular safety.