A Rare Case of Reversible Cardiac Dysfunction Associated with Tegafur/Gimeracil/Oteracil (S-1) Therapy.

For the past 20 years, S-1 has been used in the treatment of many types of cancer. However, the clinical importance of myocardial dysfunction attributed to S-1 remains to be unclear. Thus, in this study, we report on a patient with myocardial dysfunction associated with S-1.S-1 postoperative chemotherapy for gastric cancer was included as a treatment for a 65-year-old man. On day 8, S-1 treatment was discontinued after the patient developed an oral ulcer. He was then admitted to the hospital because of diarrhea caused by S-1. At approximately the same time, he developed dyspnea, and his chest X-rays revealed perihilar vascular engorgement and cardiac enlargement. Although his brain natriuretic peptide was 595.8 pg/mL, troponin I and creatine phosphokinase were unremarkable. Electrocardiograms showed no change in atrial fibrillations or new ST-T wave change. As per his transthoracic echocardiogram, noted were expansion of the left ventricle, global hypokinesis, and reduced left ventricular ejection fraction (approximately 40%). The patient was then diagnosed with S-1-related myocardial dysfunction. Furosemide, human atrial natriuretic peptide, dobutamine, enalapril, spironolactone, and bisoprolol were administered. Thirteen days after being diagnosed with heart failure, his symptoms disappeared, his echocardiogram showed that the left ventricular ejection fraction had increased to 65%, and the cardiothoracic ratio improved to 47% according to his chest X-rays.S-1-related myocardial dysfunction may be reversible, as it can improve after approximately 2 weeks.