Tetralogy of Fallot with absent pulmonary valve

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Pathophysiology

Tetralogy of Fallot with absent pulmonary valve is a rare form of tetralogy of Fallot in which there is complete absence of the pulmonary valve, with resultant severe pulmonary regurgitation. Patients with this syndrome typically exhibit massive aneurysmal dilatation of the central pulmonary arteries, which can lead to compression and obstruction of the large central airways. Clinical symptoms are typically those of respiratory distress, often complicated by recurrent pneumonia. Some children may also be cyanotic if the pulmonary annulus and infundibulum are small. Presentation is less dramatic in patients without bronchial compression.

Surgical technique

Timing of surgical intervention is dictated by the severity of respiratory insufficiency. In severe cases, neonatal intervention may be required, possibly including extracorporeal membrane oxygenation (ECMO) if the patient cannot be effectively venti- lated. In patients with less severe disease, elective surgery can be postponed for several months.

Repair of tetralogy of Fallot with absent pulmonary valve is performed through median sternotomy with cardiopulmonary bypass and aortic cross-clamping. Repair requires resection of any sub-annular obstruction within the right ventricle. The ventricular septal defect then is closed with a patch. The branch pulmonary arteries are downsized with plication and/ or resection of part of the pulmonary artery wall. To minimize airway compression, the pulmonary artery bifurcation can be relocated anterior to the aorta (the LeCompte maneuver), typically in combination with plication or reduction arterioplasty. In some cases, the main pulmonary artery is resected and replaced with an allograft valved conduit. In other cases, a transannular patch with a monocusp pulmonary valve is inserted. A small atrial septal defect is left open or created when right ventricular dysfunction is present postoperatively. Following weaning from cardiopulmonary bypass, transesophageal echocardiography is performed to assess adequacy of repair. Cardiopulmonary bypass time and aortic cross-clamp time required to complete the repair are usually moderate.

Postoperative considerations

The postoperative course following repair of tetralogy of Fallot with absent pulmonary valve is variable, depending chiefly on the degree of preoperative airway compromise and the degree of hemodynamic support required preoperatively. Invasive monitors used include arterial and central venous catheters. An LA line is used when needed for hemodynamic management. LA pressure acts as a surrogate for left ventricular end diastolic pressure, an excellent indicator of left ventricular performance. Non-invasive monitors include NIRS (near infrared spectroscopy) probes to assess adequacy of regional and global perfusion and traditional pulse oximetry. Vasoactive agents might include epinephrine and/or milrinone. Numerous other agents are available and are tailored to the specific needs of the patient, target- ing adequate oxygen delivery to the tissues of the body and optimization of cardiac output. ECMO is occasionally needed.

Postoperative complications can include bleeding, especially when extensive pulmonary artery suture lines are required. Atrioventricular conduction abnormalities can occur since ventricular septal defect closure requires placing sutures near the conduction system. Temporary pacing capability should be readily available. Persistent respiratory insufficiency may occur, necessitating prolonged mechanical ventilation. While compression of the airway will have been relieved at the time of surgery, significant airway malacia will likely remain and can take weeks or even months to resolve completely. Pleural effusions are sometimes encountered and may require prolonged pleural drainage.

Systemic arterial oxygen saturation should be nearly normal following repair of tetralogy of Fallot with absent pulmonary valve. Left atrial pressure should be normal; right atrial pressure might be slightly elevated in the early postoperative period. This is due to temporarily decreased right ventricular performance, which is common following surgery involving the right ventricular outflow tract (particularly if resection of right ventricular muscle has been necessary). Filling pressures should approximate normal by the time of hospital discharge. Length of hospital stay expected following surgery is quite variable and depends on the severity of illness at presentation and the relative smoothness of the postoperative course.