BACKGROUND AND OBJECTIVES: Milrinone is often used in children to treat acute heart failure and prevent low cardiac output syndrome after cardiac surgery. Due to the lack of studies on the long-term milrinone use in children, the objective of this study was to assess the safety and efficacy of the current patterns of milrinone use for > or =3 days in infants and children with heart diseases. SUBJECTS AND METHODS: We retrospectively reviewed the medical records of patients aged <13 years who received milrinone for > or =3 days from January 2005 to December 2012. Patients' characteristics including age, sex, height, weight, and body surface area were recorded. The following parameters were analyzed to identify the clinical application of milrinone: initial infusion rate, maintenance continuous infusion rate, total duration of milrinone therapy, and concomitantly infused inotropes. The safety of milrinone was determined based on the occurrence of adverse events such as hypotension, arrhythmia, chest pain, headache, hypokalemia, and thrombocytopenia. RESULTS: We assessed 730 admissions (684 patients) during this period. Ventricular septal defects were the most common diagnosis (42.4%) in these patients. Milrinone was primarily used after cardiac surgery in 715 admissions (97.9%). The duration of milrinone treatment varied from 3 to 64.4 days (> or =7 days in 149 admissions). Ejection fraction and fractional shortening of the left ventricle improved in patients receiving milrinone after cardiac surgery. Dose reduction of milrinone due to hypotension occurred in only 4 admissions (0.5%). Although diverse arrhythmias occurred in 75 admissions (10.3%), modification of milrinone infusion to manage arrhythmia occurred in only 3 admissions (0.4%). Multivariate analysis indicated that the development of arrhythmia was not influenced by the pattern of milrinone use. CONCLUSION: Milrinone was generally administered for > or =3 days in children with heart diseases. The use of milrinone for > or =3 days was effective in preventing low cardiac output after cardiac surgery when combined with other inotropes, suggesting that milrinone could be safely employed in pediatric patients with heart diseases.