Congenital Heart Defects

Congenital heart defects are broadly grouped by whether they cause cyanosis. Acyanotic defects (such as atrial septal defect, ventricular septal defect, and patent ductus arteriosus) typically involve a left-to-right shunt, where oxygenated blood recirculates back into the pulmonary circulation rather than out to the body — these children are often not visibly blue, but can develop signs of heart failure (poor feeding, sweating with feeds, poor weight gain, tachypnea) from the extra volume the heart and lungs must handle. Cyanotic defects (such as tetralogy of Fallot and transposition of the great arteries) involve a right-to-left shunt or abnormal blood flow that sends deoxygenated blood out to the body, causing visible cyanosis — tetralogy of Fallot is a particularly high-yield combination of four defects and is associated with "tet spells" (sudden episodes of worsening cyanosis, often triggered by crying, feeding, or straining), managed acutely by placing the infant in a knee-to-chest position, which increases systemic vascular resistance and improves blood flow to the lungs.