Purpose of Palliative Shunt Surgery in Complex Congenital Heart Defects
Palliative shunt surgery is performed to relieve symptoms and ameliorate adverse effects of congenital heart anomalies by modifying blood flow patterns when complete anatomic repair is not immediately possible or advisable. 1
Types and Purposes of Palliative Shunts
Palliative shunt procedures can be categorized based on their primary hemodynamic goals:
1. Increasing Pulmonary Blood Flow (for Pulmonary Oligemia)
- Systemic-to-Pulmonary Artery Shunts:
- Modified Blalock-Taussig Shunt: Creates an anastomosis between a subclavian artery and ipsilateral pulmonary artery using an interposition tube graft (typically polytetrafluoroethylene) 1, 2
- Classic Blalock-Taussig Shunt: Direct end-to-side anastomosis between subclavian artery and pulmonary artery 1
- Potts Shunt: Creates a communication between pulmonary artery and descending thoracic aorta 1
- Waterston Shunt: Creates a communication between ascending aorta and right pulmonary artery 1
These shunts increase pulmonary blood flow and enhance systemic oxygen saturation in patients with cyanotic heart defects, such as tetralogy of Fallot 1, 2.
2. Decreasing Pulmonary Blood Flow (for Pulmonary Overcirculation)
- Pulmonary Artery Banding: Creates a surgically induced stenosis of the main pulmonary artery to protect the lungs against high pulmonary blood flow and pressure 1, 2
- Norwood Procedure: Used for hypoplastic left heart syndrome, involving aortic arch reconstruction with a systemic-to-pulmonary arterial shunt 1
3. Enhancing Intracardiac Blood Mixing (for Systemic Hypoxemia)
- Atrial Septostomy Procedures:
4. Staged Palliation for Single Ventricle Physiology
- Glenn Shunt (Cavopulmonary Shunt): Anastomosis of superior vena cava to pulmonary artery, increasing pulmonary blood flow without volume loading the single ventricle 1, 3
- Fontan Procedure: Diversion of systemic venous return directly to pulmonary artery, normalizing systemic oxygen saturation 1
Clinical Benefits and Outcomes
Palliative shunt procedures provide several important benefits:
- Improved Oxygenation: Systemic-to-pulmonary shunts can increase arterial oxygen saturation from approximately 67% to 85% 4
- Reduced Polycythemia: Hemoglobin concentration can decrease from 190 g/L to 136 g/L after shunt placement 4
- Pulmonary Artery Development: Systemic-to-pulmonary shunts can promote growth of hypoplastic pulmonary arteries 4
- Bridge to Definitive Repair: Provides time for patient growth before complete anatomic correction 2
- Symptom Relief: Reduces cyanosis and improves exercise tolerance 2
Complications and Considerations
Palliative shunts carry significant risks that must be monitored:
- Thrombosis: A major cause of shunt failure, particularly in systemic-to-pulmonary shunts (9.3% overall failure rate) 1
- Distortion: Can occur in 38% of cases requiring intervention 1
- Pulmonary Vascular Disease: Excessive pulmonary blood flow can lead to pulmonary vascular obstructive disease 1
- Pleural Effusions: Particularly after cavopulmonary anastomosis, can lead to protein loss and increased thrombosis risk 1
- Mortality Risk: Patients requiring early shunt intervention have significantly lower 5-year survival (41.2% vs 76.8%) 1
Imaging and Monitoring
Multimodality imaging plays a crucial role in monitoring these patients:
- Echocardiography is first-line for routine follow-up
- CT and MRI provide complementary information for detecting complications and planning subsequent procedures 5
Emerging Approaches
Recent developments include:
- Growing trend toward interventional techniques with stent deployment as alternatives to surgical shunts 2
- Investigation of autologous umbilical vessels as potential shunt material to reduce thrombosis risk and allow for growth 6
Palliative shunt procedures remain essential in the management of complex congenital heart defects, particularly in emergency settings or when complete repair is not immediately feasible. The choice of specific shunt type should be based on the underlying cardiac anatomy, patient size, and long-term surgical plan.