Newborns and infants with TOF or PA/VSD are cyanotic due to the right-to-left shunt through the ventricular septal defect and decreased pulmonary blood flow. The degree of hypoxemia is proportional to the volume of pulmonary blood flow which is related to the severity of right ventricular outflow tract obstruction (RVOTO) and any additional sources of pulmonary blood flow (including a patent ductus arteriosus and systemic-to-pulmonary artery collateral vessels). Because patients with PA/VSD have no forward blood flow from the right ventricle into the pulmonary artery, survival is totally dependent upon pulmonary blood flow from a patent ductus arteriosus and/or MAPCAs. This may or may not be the case in TOF depending upon the severity of RVOTO.

Infants with tetralogy of Fallot or PA/VSD come to medical attention because of cyanosis or a murmur soon after birth.

Most patients with tetralogy of Fallot or PA/VSD will be cyanotic. However, in some, the degree of cyanosis may be minimal (the so-called pink tetralogy) and not apparent on physical examination. The right ventricular impulse will be increased at the right lower sternal border. The first heart sound will be normal but the second heart sound will be increased in intensity and frequently single. There is an increased right ventricular impulse at the lower left sternal border. In TOF here is a systolic ejection murmur along the left sternal border. In PA/VSD because there is not a patent RV outflow tract, there is not a systolic ejection murmur. However, one may hear a systolic murmur created by flow through the MAPCAs.

In approximately 25 % of patients, a right aortic arch will be apparent on the chest radiograph. Hypoplasia of the main pulmonary artery and right ventricular hypertrophy may produce the “coeur en sabot” (boot shaped) configuration of the cardiac silhouette, but this is not a particularly helpful sign in an infant

The diagnosis of tetralogy of Fallot or PA/VSD, the presence and size of the patent ductus arteriosus, and the size of the main and central right and left pulmonary arteries can be established using two-dimensional echocardiography. Angiography may be necessary to ascertain the size and distribution of the peripheral pulmonary arteries, the presence or absence of peripheral pulmonary stenosis, the presence and anatomy of MAPCAs, and the presence of additional ventricular septal defects.

Initial management of patients with TOF and PA/VSD involves establishing important details of the anatomic diagnosis and treating the hypoxemia and acidosis if they are significant. Severely hypoxemic infants should be treated with an infusion of prostaglandin E_l to reopen the ductus arteriosus or maintain its patency. If pulmonary blood flow is inadequate, a systemic-to-pulmonary artery anastomosis should be established surgically. A Blalock-Taussig (subclavian artery to pulmonary artery anastomosis) or modified Blalock-Taussig (interposition of a Gore-Tex tube from the subclavian artery to the pulmonary artery) is the procedure of choice. Intracardiac repair of tetralogy of Fallot or PA/VSD usually is performed between ages 3 and 12 months. Intracardiac repair involves closure of the ventricular septal defect and relief of the RVOTO or atresia. The latter may necessitate patch enlargement of the right ventricular outflow tract, pulmonary annulus, or both or insertion of a valve containing conduit from the right ventricle to the pulmonary artery.