Management of a Patient with Left-to-Right Shunt

We describe the basic pathophysiology of common congenital heart defects with left-to-right shunt. These defects include ostium primum atrial septal defect (ASD), ostium secundum ASD, sinus venosus ASD, coronary sinus ASD, ventricular septal defects, atrioventricular septal defects, patent ductus arteriosus, and aortopulmonary window. The underlying pathophysiology of these defects is a communication between the systemic and pulmonary circulations. This communication allows return of oxygenated blood back to the lungs (left-to-right shunt) leading to volume overload of the right heart and lungs. The amount of shunting determines the degree of symptoms and depends on the size of the defect and the resistance and pressure properties of the pulmonary and systemic circulations. Unrecognized large left-to-right shunts can lead to irreversible pulmonary vascular disease and Eisenmenger syndrome. Medical management includes careful attention to fluid balance, avoidance of indiscriminate oxygen therapy, and appropriate use of inotropic agents, systemic afterload reduction, and positive pressure ventilation.