2. Palliative surgery
2.1 B-T shunt
Dr. Alfred Blalock created the B-T shunt operation in 1948 with the support of pediatric cardiologist Helen B Taussig and surgical technician Vivien Thomas. For patients with pulmonary obstruction, pulmonary dysplasia, and severe hypoxia, the B-T shunt operation can be performed to improve pulmonary circulation and promote pulmonary vascular development. After 6 months of age, pulmonary vascular resistance and PA development may be evaluated to determine the feasibility of a bidirectional Glenn operation.10
2.2 PA banding
For patients with restricted pulmonary circulation, a pulmonary loop surgery should be performed within 2 - 3 months to protect the pulmonary vascular bed and prevent the development of pulmonary hypertension.11 If the PA pressure is satisfactorily reduced, a bidirectional Glenn operation may be performed after 6 months of age.12
2.3 Norwood Operation
Dr. Norwood developed a series of operations to treat fetuses with hypoplastic left heart syndrome (HLHS) and achieved appreciable outcomes. Since then, Norwood’s operation has been widely adopted with great success worldwide.13 Norwood’s techniqueis one of the effective treatments for HLHS and left ventricular outflow tract obstruction complicated by SV. The Norwood operation contains three phases: phase I consists of palliative care with Norwood-type surgery in the neonatal period, phase II consists of a Glenn operation, and phase III consists of a full lumen operation.15
2.4 Glenn Operation
Dr. Glenn performed the first superior vena cava-right PA anastomosis for tricuspid regurgitation in 1958.15 The bidirectional Glenn operation is a form of bidirectional superior vena cava pulmonary anastomosis, in which the proximal end of the superior vena cava is cut off, sutured, and closed, and the distal end has an end-to-side anastomosis with the right PA. If the left superior vena cava persists, the left superior vena cava and the left PA should be anastomosed at the same time. The Glenn operation is an important part of the series of palliative operations for SV treatment. It has been reported that the bidirectional Glenn operationfacilitates long-term remission in patients with a single functioning ventricle.16
2.5 Fontan Operation
It has been nearly 50 years since Dr. Fontan first described the Fontan operation in 1971.17 The traditional Fontan operation is performed by connecting the right atrium to the PA, suturing the tricuspid valve, and directly draining the vena cava blood to the lung. At present, the traditional Fontan operation is rarely used. A modified Fontan operation that consists of caval-pulmonary anastomosis was introduced and involves the intracardiac tunnel, intracardiac duct, and extracardiac total lumen-PA connection. At present, the most common clinical application of this technique is the extracardiac conduit of total cavopulmonary connection (ECTCPC). This surgical approach reduces the need for anoperation in the right atrium, avoids high right atrial pressure, and eventually reduces the incidence of early and mid-term arrhythmia after other surgical procedures.18 The Fontan cycle is characterized by increased vena cava pressure, decreased non-pulsating pulmonary blood flow, decreased ventricular preload, and increased postload.19 However, in the long run, the Fontan circulation is a non-physiological state, in which patients’ tolerance to exercise and hemodynamic response are compromised, which can lead to various complications and affect the long-term prognosis.20 Broad Fontan circulatory failure can be classified into three categories: ventricular dysfunction, systemic complications of Fontan physiology (such as plastic bronchitis and protein-loss bowel disease), and chronic Fontan circulatory failure.21 Additional complications associated with Fontan surgery include an increased risk of stroke, protein-loss bowel disease, and arrhythmia without survival improvements.16 Despite these potential complications, the Fontan series of operations is still a common and effective method for SV treatment. When the Fontan series of operations and medical treatments are ineffective, the only choice for SV treatment is heart transplantation.