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A systemic-to-pulmonary artery shunt is the mainstay of palliative surgical therapy for children with cyanotic congenital heart disease. These shunts are mainly used to maintain stable blood flow to the pulmonary arteries as part of palliation in patients with single ventricle physiology, to postpone a definitive biventricular repair, and to promote the growth of the branch pulmonary arteries (PAs). Current options for systemic-to-pulmonary artery shunts include ductal stenting, systemic aortopulmonary shunts, and central aortopulmonary shunts (CAPS). Patent ductus arteriosus stents are selectively used for hybrid palliation in patients with hypoplastic left heart syndrome. The original aortopulmonary shunt, the classic Blalock-Taussig–Thomas shunt, was developed in 1944 and involves a direct end-to-side anastomosis between the transected subclavian and pulmonary arteries. This shunt is rarely used today due to complications with limb ischemia.[1][2] The modified Blalock-Taussig-Thomas shunt (mBTT), developed in the 1970s, uses a polytetrafluoroethylene (PTFE) shunt between the patient's subclavian and pulmonary arteries.[3] The mBTT shunt offers several advantages over the classic BTT, including preservation of the circulation to the arm, regulation of shunt flow by the size of the shunt, guaranteed graft length, and ease of shunt takedown. Adding heparin-coated grafts has contributed greatly to the longevity of the shunts.[3][4] In 1946, Potts introduced a CAPS, a direct anastomosis between the aorta and a central pulmonary artery, as a palliative surgical option for neonates with underdeveloped pulmonary vasculature in whom the BTT shunt was not feasible. The Potts shunt, a direct anastomosis between the descending aorta and left pulmonary artery, was often associated with excessive pulmonary blood flow. In addition, circulatory arrest with deep hypothermia is typically required at the time of the takedown of the Potts shunt. In 1948, Robert Gross pioneered using arterial homografts to extend the short subclavian artery. Almost a decade later, Alexander Vishnevsky, a prominent surgeon at the Institute of Surgery in Moscow, published an article detailing his experience using arterial homografts in performing Blalock–Taussig shunts on 31 patients, which paved the way for the modified version of the classic BTT to see the light.

In 1946, Potts introduced a CAPS, a direct anastomosis between the aorta and a central pulmonary artery, as a palliative surgical option for neonates with underdeveloped pulmonary vasculature in whom the BTT shunt was not feasible. The Potts shunt, a direct anastomosis between the descending aorta and left pulmonary artery, was often associated with excessive pulmonary blood flow. In addition, circulatory arrest with deep hypothermia is typically required at the time of the takedown of the Potts shunt. In 1948, Robert Gross pioneered using arterial homografts to extend the short subclavian artery. Almost a decade later, Alexander Vishnevsky, a prominent surgeon at the Institute of Surgery in Moscow, published an article detailing his experience using arterial homografts in performing Blalock–Taussig shunts on 31 patients, which paved the way for the modified version of the classic BTT to see the light. In 1962, Klinner et al from Germany first used Teflon for mBTT, but it was de Leval who promoted the procedure and formally coined the term mBTT after publishing results from 99 patients treated with Dacron and polytetrafluorethylene (PTFE) in 1981. In 1964, the Waterston or Waterston-Cooley shunt was introduced, involving a direct anastomosis between the ascending aorta and the right pulmonary artery. However, it was later discovered to be associated with shunt failure, distortion of the right pulmonary artery at the site of anastomosis, lack of growth in the main and left pulmonary arteries, and congestive heart failure. Ultimately, both central shunts fell out of favor as they were fraught with complications, and the mBTT shunt became the default intervention for such cases.[3][5][6][7]

In 1962, Klinner et al from Germany first used Teflon for mBTT, but it was de Leval who promoted the procedure and formally coined the term mBTT after publishing results from 99 patients treated with Dacron and polytetrafluorethylene (PTFE) in 1981. In 1964, the Waterston or Waterston-Cooley shunt was introduced, involving a direct anastomosis between the ascending aorta and the right pulmonary artery. However, it was later discovered to be associated with shunt failure, distortion of the right pulmonary artery at the site of anastomosis, lack of growth in the main and left pulmonary arteries, and congestive heart failure. Ultimately, both central shunts fell out of favor as they were fraught with complications, and the mBTT shunt became the default intervention for such cases.[3][5][6][7] In 1987, Barragry et al reported promising results using a PTFE graft between the aorta and the main pulmonary artery.[8] Subsequently, the Mee (or Melbourne) shunt was created for patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collaterals with diminutive pulmonary stenosis. In this technique, the central PA is transected from its proximal origin and reimplanted directly to the lateral wall of the aorta with an end-to-side anastomosis.[9] In recent years, CAPS has gained popularity, particularly in patients with hypoplastic pulmonary arteries.[10][11] The Society of Thoracic Surgeons database reports that central shunts account for 32% of systemic-to-pulmonary shunts, serving as a bridge to either univentricular or biventricular repair in patients with small, confluent, and normally arborized intrapericardial branch PAs.[10][12]

Post-operative care is critical in the first 24 hours. Short-term risks include overcirculation, persistent cyanosis, or shunt thrombosis. Intensive care unit care is required to balance the blood flow to the lungs and systemic circulation. Medical management includes careful attention to vent management, fluid administration, vasoactive agents, and optimization of hematocrit. Patients should be anticoagulated 24 to 72 hours post-procedure to decrease the risk of shunt thrombosis.[10] The Society of Thoracic Surgeons Congenital Heart Surgery Database revealed that 33% of all shunt deaths occurred in the first 24 hours.[12] Aspirin (10 mg/kg) should be given when the shunt is created and until the shunt is taken down.[4][25] Patency of the shunt ranges from 1 to 4 years.[10] Risk factors for late mortality (90 days) in patients undergoing systemic to pulmonary shunts include lower body weight, preoperative ventilator support, right atrial isomerism and coexistence of major aortopulmonary collateral arteries, and an unbalanced atrioventricular septal defect.[26]

Patients with congenital heart disease undergoing CAPS will require lifelong multidisciplinary medical care. The care of these complex cyanotic congenital heart defects occurs in neonates, children, adolescents, and adults. This requires coordinated efforts from a team of caregivers, including ancillary staff, respiratory therapists, neonatal and pediatric nurses, pediatric and adult specialists such as pediatric cardiologists and intensivists, adult congenital heart disease specialists, and congenital cardiac surgeons.