This study is testing if a drug called **milrinone** can help babies' hearts work better after a procedure to fix a heart problem called PDA (Patent Ductus Arteriosus). Milrinone is a medicine that helps the heart pump blood more effectively. Babies in the study will either get milrinone or a placebo (a saltwater solution that doesn't have any medicine). The study looks at how this affects the babies' survival and development over two years. **Key Points:** - Babies will receive the study drug for up to 5 days, depending on their needs and reactions. - Close monitoring will happen for the first few hours to check for side effects. - A follow-up visit will be scheduled about two years later to assess the child's development and health. Babies eligible for this study are born very early (≤27 weeks) and need a procedure to manage their PDA. They should not have severe kidney issues or other major heart problems. If your baby meets these conditions, participating in this study might help improve their heart function and overall health.