Milrinone for Prevention of Post-ligation Cardiac Syndrome Trial

Inclusion Criteria:

* Gestational age at birth ≤27 weeks (and 6 days) and postnatal age \< 3 months at intervention
* Invasive or non-invasive positive pressure respiratory support (does not include low flow nasal cannula)
* Hemodynamically significant PDA with minimum transductal diameter ≥1.0 mm within 2 days of intervention
* Decision by clinical team to proceed with PDA closure via surgical ligation or percutaneous cardiac catheterization based on clinical and echocardiography features of hemodynamic significance.

Exclusion Criteria:

* Any major congenital malformation
* Congenital heart disease (except small (≤1mm) muscular ventricular septal defects, or small/moderate (\<3mm) atrial septal defect)
* Acute renal failure defined by urine output \< 0.5 mL/kg/hour OR rise of serum creatinine by 0.3 mg/dL within 48 hours OR rise of serum creatinine more than 40% above baseline serum creatinine within prior 72 hours.
* Systemic administration of vasodilator/inodilator agents
* Prior history of arrhythmia