31. DIRECT MEDICAL COSTS IN THE TREATMENT OF HEART FAILURE AT SOME HOSPITALS IN NORTHERN VIETNAM IN 2023: AN ANALYSIS FROM THE PERSPECTIVE OF HEALTH SYSTEM. YHCĐ [Internet]. 2025 Jan. 7 [cited 2026 Sept. 9];66(1). Available from: https://tapchiyhcd.vn/index.php/yhcd/article/view/1935