What are the characteristics of Tetralogy of Fallot (TOF) with pulmonary atresia?

From the Guidelines

Tetralogy of Fallot with pulmonary atresia is a severe congenital heart defect characterized by the four classic features of Tetralogy of Fallot with complete obstruction of the pulmonary valve, requiring surgical intervention for survival. This condition combines ventricular septal defect, overriding aorta, right ventricular hypertrophy, and right ventricular outflow tract obstruction with complete obstruction (atresia) of the pulmonary valve, preventing blood flow from the right ventricle to the lungs 1. The characteristics of TOF with pulmonary atresia include:

• Varying levels of severity and a morphological spectrum
• A single and large VSD, usually in the subaortic position
• A small and stenotic pulmonary valve
• Frequent pulmonary artery anomalies, including hypoplasia and stenosis
• Associated anomalies, such as a secundum ASD, AVSD, and a right aortic arch in approximately 25% of cases
• Coronary artery anomalies, most commonly with a left anterior descending coronary artery 1.

Treatment involves a staged surgical approach, typically beginning with a palliative procedure in early infancy, such as placement of a Blalock-Taussig shunt to provide pulmonary blood flow. Complete repair is usually performed between 3-6 months of age, involving closure of the ventricular septal defect and establishing continuity between the right ventricle and pulmonary arteries using a conduit or homograft. Patients require lifelong cardiac follow-up as they often need subsequent surgeries to replace conduits as they grow. Medical management includes prophylactic antibiotics to prevent endocarditis, diuretics for heart failure symptoms, and close monitoring for cyanosis, growth, and development. The condition's severity stems from the complete blockage of blood flow to the lungs, making it incompatible with life without intervention. Pulmonary blood flow in these patients initially depends on a patent ductus arteriosus and may require prostaglandin E1 infusion immediately after birth to maintain this critical pathway until surgical intervention. Recent guidelines also emphasize the importance of imaging in assessing the severity of pulmonary regurgitation and determining the optimal timing for pulmonary valve replacement 2.

From the Research

Characteristics of Tetralogy of Fallot with Pulmonary Atresia

• Tetralogy of Fallot with pulmonary atresia (ToF-PA) is a rare and complex congenital heart defect characterized by complete failure of forward flow from the right ventricle to the pulmonary arterial system 3.
• The pathophysiology of ToF-PA is largely attributable to the abnormalities of the pulmonary vasculature, with pulmonary blood flow being entirely dependent on shunting from the systemic circulation 3.
• Patients with ToF-PA differ in terms of the sources of pulmonary blood flow, which can include a patent ductus arteriosus, major aortopulmonary collaterals, or a combination of the two 4.
• The variability in the origin, size, number, and clinical course of major aortopulmonary collateral arteries (MAPCAs) adds to the complexity of these patients 4.
• The goal of management is to establish pulmonary blood flow from the right ventricle with right ventricular pressures that are ideally less than half of the systemic pressure to allow for closure of the ventricular septal defect 4.

Anatomical and Physiological Findings

• ToF-PA is characterized by an extraordinarily heterogeneous group of complex anatomical findings, including diverse sources of flow of blood to the lungs, which often include multiple systemic-to-pulmonary collateral arteries 3, 5.
• The native intrapericardial pulmonary arterial circulation can be absent or diminutive, and the flow of blood to the lungs can be derived exclusively from the intrapericardial pulmonary arteries, exclusively from systemic-to-pulmonary collateral arteries, or from both 5.
• Patients with ToF-PA are at higher risk for reinterventions to address pulmonary arterial or RV-pulmonary artery conduit stenosis, progressive aortic root dilation and aortic insufficiency, and late mortality than those with less severe forms of ToF 4.

Management and Treatment

• An individualized approach to the surgical treatment of ToF-PA is necessary, taking into account the source of pulmonary arterial flow and the complexity of the pulmonary vasculature 5.
• Unifocalization and aggressive attempts to recruit the available native pulmonary vasculature can achieve outcomes in the intermediate term superior to the natural history of the lesions 6.
• Complete biventricular repair can be achieved in the majority of patients, with a low rate of reoperation and mortality 5.
• Long-term survival rates are excellent, but adult survivors with ToF-PA may require reintervention, surgically or catheter-based 7.