Congenital Cardiac Surgery: Shunts, Ducts, and Timing
Congenital Cardiac Surgery - Shunts, Ducts, and Timing
Organize congenital lesions by physiology rather than by name. Cyanotic lesions with decreased pulmonary blood flow (tetralogy of Fallot, pulmonary atresia) require ductal patency; ductal-dependent lesions improve with prostaglandin E1. Ductal-dependent systemic circulation (hypoplastic left heart syndrome, critical coarctation, interrupted aortic arch) is different: these infants may need PGE1 to keep the ductus open for systemic perfusion, and overoxygenation can lower pulmonary vascular resistance and steal flow. The hyperoxia test helps but is not absolute. Understand shunt direction: a ventricular septal defect with high pulmonary vascular resistance can reverse to Eisenmenger physiology, making closure contraindicated. Timing rules matter: large VSDs with heart failure are repaired in infancy; tetralogy of Fallot repair is typically elective in the first year; transposition of the great arteries requires early arterial switch, often with balloon atrial septostomy. The Fontan pathway is staged, and candidates need low pulmonary vascular resistance and adequate ventricular function.
Worked example/rule of thumb: a cyanotic newborn with a ductal-dependent lesion should receive PGE1 and be kept on minimal supplemental oxygen while awaiting echocardiography and transfer. Rule of thumb: in congenital heart disease, ask first whether the ductus is keeping the patient alive - and whether it is supplying the lungs or the body.