The Blalock-Taussig shunt is a surgical procedure used to improve blood flow to the lungs in patients with certain congenital heart defects, such as Tetralogy of Fallot. It involves creating a connection between the subclavian artery and the pulmonary artery, allowing more oxygen-rich blood to reach the lungs for oxygenation. This procedure is often performed in infants and young children who are not yet candidates for more complex heart surgeries. The Blalock-Taussig shunt can provide temporary relief from symptoms and improve overall health until a more definitive surgical repair can be done.