Balloon atrial septostomy is a minimally invasive procedure used to create or enlarge an opening in the atrial septum, the wall separating the heart's left and right atria. This procedure is often performed in infants with certain congenital heart conditions, such as transposition of the great arteries or hypoplastic left heart syndrome, where it helps improve oxygenation by allowing blood to mix between the atria. During the procedure, a catheter with a balloon at its tip is guided through a blood vessel, typically in the groin, to the atrial septum. The balloon is then inflated to create or enlarge an opening. This temporary measure can provide symptomatic relief and improve survival rates in critical situations until a definitive surgical repair can be performed. Risks include bleeding, infection, or damage to the heart structures, and close follow-up care is essential to monitor the patient's response.