In cyanotic CHD associated with diminished pulmonary blood flow, palliative procedures have been aimed at increasing pulmonary blood flow by directly or indirectly shunting blood from the systemic veins or systemic circulation. These procedures have continued to evolve.

The Fontan procedure (with its many modifications), the final common pathway for single ventricle repair, obviates the need for an RV by rerouting the venous return from the superior and inferior vena cava directly to the pulmonary circulation, thus separating the systemic and pulmonary venous return. This operation was originally used in patients with tricuspid atresia but currently is the palliative procedure of choice for a variety of congenital heart defects, including hypoplastic left heart syndrome and morphologic single ventricle when the pulmonary bed has been protected by congenital or palliative (ie, pulmonary band) stenosis. The Fontan procedure performed in adulthood carries a relatively low perioperative risk and leads to relief of cyanosis and improved functional class. However, arrhythmias, protein-losing enteropathy, and progressive systemic ventricular dysfunction remain ongoing concerns. The extracardiac Fontan procedure (direct cavopulmonary anastomosis) may decrease the incidence of arrhythmias. Thromboembolic disease is also a major cause of morbidity and mortality among patients after the Fontan procedure, and this recognition has led some cardiologists to advocate prophylactic anticoagulation in these patients. However, insufficient data exist to support a blanket recommendation on this issue. The modified, or bidirectional, Glenn procedure (superior vena cava to confluent pulmonary artery) can be used as a staging procedure for a future Fontan procedure or as a palliative shunt that can increase pulmonary blood flow when a Fontan is contraindicated because of poor ventricular function. Because right atrial distention does not occur, atrial arrhythmias may be less common.

In cyanotic patients with inadequate pulmonary blood flow (eg, TOF, pulmonary and tricuspid atresia), early surgical systemic-to-pulmonary shunts are life-saving procedures. The Waterston (ascending-aorta-to-pulmonary-artery) and Potts (descending-aorta-to-pulmonary-artery) shunts have been largely abandoned because of the high frequency of pulmonary hypertension, stenosis distal to the shunt sites, and considerable difficulty with surgical take down, but adult patients with these types of shunts are still infrequently encountered. Pulmonary artery pressure can be estimated noninvasively using the brachial artery systolic cuff pressure and continuous wave Doppler echocardiography to measure the gradient between aorta and pulmonary artery across the shunt. The classic Blalock-Taussig shunt (subclavian artery anastomosed to the pulmonary artery) has a much lower risk of pulmonary vascular disease, with preferential blood flow into one lung (usually the left). Even when pulmonary vascular disease develops in the ipsilateral lung, the other lung is usually protected and late intracardiac repair may be possible. Because the subclavian artery is diverted, the ipsilateral arm is pulseless. The modified Blalock-Taussig shunt (now more commonly performed) uses a synthetic conduit and maintains perfusion to the arm. These shunts can become obstructed with recurrence of cyanosis, loss of the continuous murmur on physical examination, and decreased flow on Doppler echocardiography.

In the Rastelli procedure, extracardiac conduits from the right ventricle to the pulmonary artery may be used in pulmonary atresia and CC-TGA with PS, truncus arteriosus, and double-outlet RV with PS. They can be synthetic (heterograft) or cadaveric (homograft) and may or may not contain valves. Problems are caused by valvular obstruction or degeneration and obstruction of shunts, baffles, and conduits. Continued clinical and noninvasive follow-up is essential in this group of patients.