Aortopulmonary Window Surgery 

Updated: Jun 24, 2021
Author: Mary C Mancini, MD, PhD, MMM; Chief Editor: Suvro S Sett, MD, FRCSC, FACS 

Overview

Background

Aortopulmonary window (APW) is a defect between the great vessels that results from failure of the conotruncal ridges to fuse. It is separate from truncus arteriosus in that it is associated with essentially normal aortic and pulmonary valves. The defect usually begins just above the sinuses of Valsalva and then extends a variable distance distally into the arch.[1]

For patient education resources, see the Heart Health Center, Aortic Aneurysm of the Abdomen and Thorax (Chest) and Congestive Heart Failure.

History of the Procedure

Aortopulmonary window was first described in the 19th century, and the first repair was performed in 1952 by Robert E. Gross, MD, at Boston Children's Hospital.[2] Subsequent development of cardiopulmonary bypass techniques simplified the repair. Currently, an incision directly into the aortopulmonary window or the aorta is used. Most lesions are repaired by direct patch repair of the defect.

Problem

Aortopulmonary window produces a large and usually unrestricted left-to-right shunt that worsens as pulmonary vascular resistance falls during the newborn period. Congestive heart failure and low cardiac output can rapidly follow. These patients are particularly susceptible to Eisenmenger syndrome at an early age because of combined systolic and diastolic run-off into the pulmonary circulation. Aortopulmonary window is frequently associated with other cardiac defects that affect outcome and complicate repair.

Epidemiology

Aortopulmonary window may occur as an isolated lesion or as part of a larger complex of lesions and represents approximately 0.2% of all congenital cardiac lesions. Two of the largest series reported, from Boston Children's Hospital and Northwestern University, show that an active center can expect about one case per year.[3]

Etiology

Aortopulmonary window represents a failure of the conotruncus to differentiate into the aorta and pulmonary artery. No genetic associations or environmental risk factors are known. The two competing embryologic theories are (1) that aortopulmonary window is part of a spectrum of conotruncal abnormalities, which includes truncus arteriosus at one end of the spectrum, and (2) that aortopulmonary window is unrelated to truncus arteriosus because the lesions associated with each defect are so dissimilar.

Pathophysiology

The hemodynamic abnormalities are similar to those seen with a large, unrestrictive ventricular septal defect (VSD) or patent ductus arteriosus. Aortopulmonary window is characterized by a large left-to-right shunt that becomes progressively worse as pulmonary vascular resistance falls during the newborn period. Volume overload and pulmonary overcirculation lead to progressive left ventricular dysfunction and congestive heart failure.

The common association of distal arch obstruction or interrupted aortic arch with aortopulmonary window acts as an obstruction to systemic flow and further increases the left-to-right shunt.[4] Perfusion to the lower body therefore depends on flow through the ductus arteriosus. Closure of the ductus results in severe hypoperfusion of the lower body, pulmonary overcirculation, and impending congestive heart failure.

Presentation

The presentation depends on the size of the lesion and the systemic and pulmonary vascular resistances. As discussed above, the presence of obstructive lesions in the distal aorta increases the severity of symptoms.

Rarely, the lesions are small and restrictive, in which case the symptoms may be mild. More commonly, however, the defects are nonrestrictive, and the patient presents with congestive heart failure. Symptoms may include tachypnea, tachycardia, irritability, poor feeding, and lack of weight gain. If the shunt is sufficiently large, infants may present in severe heart failure with low cardiac output and severe acidosis.

Physical examination reveals an active precordium with a second heart sound that is accentuated and not split. A systolic murmur and widened pulse pressure are characteristic.

Patients who present after infancy have a high prevalence of pulmonary vascular hypertension and a rapid progression to Eisenmenger syndrome within the first years of life. These patients may present with milder symptoms because of improvement in the left-to-right shunt and decreased pulmonary overcirculation. Any infant older than approximately 6 months should be considered at high risk for pulmonary hypertension, and cardiac catheterization should be considered.

Indications

The presence of an aortopulmonary window (APW) is the only indication necessary for repair. Spontaneous closure is not known to occur. Delay in repair risks development of pulmonary vascular hypertension and Eisenmenger syndrome. Therefore, repair should be undertaken at the time of diagnosis and after initial stabilization.

Relevant Anatomy

Aortopulmonary window (APW) represents a spectrum defined by the distal extension of the defect. Large defects produce a confluence of the aorta and main pulmonary artery. In these patients, the branch pulmonary arteries are often abnormally positioned. In particular, the right pulmonary artery may originate from the aorta and further distal extension is associated with interrupted aortic arch (usually type A) and patent ductus arteriosus, a constellation of findings known as Berry syndrome.[5]

More than half of patients with aortopulmonary window have additional associated lesions. They range from patent ductus arteriosus and atrial septal defect (ASD) to interrupted aortic arch, tetralogy of Fallot, and total anomalous pulmonary venous drainage.[6]

The coronary arteries can arise abnormally. One or both of the coronary arteries may arise from the area of the confluence or from the pulmonary artery.[7]

Contraindications

The primary contraindications to surgery in patients with aortopulmonary window (APW) are similar to those in a patient with a large ventricular septal defect (VSD). Ideally, patients should undergo repair before the onset of pulmonary vascular hypertension. In patients older than 6 months, cardiac catheterization should be considered. If significant pulmonary hypertension is present, reversibility should be demonstrated by the administration of vasodilators. The presence of irreversible pulmonary hypertension is a contraindication to repair.

 

Workup

Laboratory Studies

No specific laboratory studies are required for diagnosis of aortopulmonary window (APW). All patients should have a complete blood count and a type and screen in anticipation of surgery. Arterial blood gas (ABG) levels should be obtained in patients receiving mechanical ventilation; PCO2 and pO2 can both be manipulated to prevent pulmonary overcirculation.

Imaging Studies

Echocardiography is usually sufficient for defining the extent of the defect and any associated anomalies.

Chest radiography reveals cardiomegaly and pulmonary congestion.

Computed tomography has been used to detect and evaluate associated conditions and congenital thoracic anomalies in neonates, infants and adults.[4, 8]

Other Tests and Diagnostic Procedures

An electrocardiogram (ECG) reveals left and right ventricular hypertrophy.

Cardiac catheterization is reserved for patients who present with aortopulmonary window later in life. Any patient older than 6 months is at risk for the development of pulmonary hypertension. If the pulmonary vascular resistance is elevated, test for reversibility with vasodilators such as oxygen or nitric oxide. Occasionally, patients with additional intracardiac abnormalities may require catheterization to fully define the anatomy.

 

Treatment

Medical Therapy

Medical therapy is focused on preoperative stabilization. Surgical correction is the only effective treatment for aortopulmonary window (APW). However there are reports of transcatheter occlusion of simple APW.[9]

Intravenous prostaglandins (eg, alprostadil) may be required to maintain patency of the ductus arteriosus in patients with interrupted aortic arch in order to provide blood flow to the lower half of the body. The associated pulmonary arterial vasodilatation may further exacerbate the increased pulmonary blood flow.

Digoxin and furosemide are frequently administered to treat the heart failure and volume overload associated with this lesion.

Inotropic agents (eg, dopamine, dobutamine) may also be required for infants with significant heart failure and low cardiac output associated with myocardial dysfunction.

Surgical Therapy

Surgery is usually the treatment for aortopulmonary window. After initial stabilization and correction of acidosis, surgery should be undertaken as soon as possible.

Surgery is performed with the use of cardiopulmonary bypass. An incision can be made into the anterior aspect of the aorta, the main pulmonary artery, or the aortopulmonary window itself.

Associated lesions are usually repaired during the same surgery. More complex repairs and myocardial protection strategies are required in patients with associated lesions, increasing the morbidity and mortality associated with the operation.

Preoperative Details

Preoperative care is centered on correction of acidosis and stabilization of the child. Congestive heart failure symptoms are treated with digoxin, furosemide, and inotropes as necessary.

Elective intubation can also be performed and pulmonary blood flow regulated by altering the inspired fractions of oxygen and carbon dioxide.

Echocardiography is performed to define the anatomy and assess ventricular function. In complex lesions or in instances in which the coronary arteries cannot be clearly seen, cardiac catheterization and/or computed tomography (CT) scanning may be required.

Patients presenting when older than 6 months need cardiac catheterization to rule out irreversible pulmonary hypertension.

Intraoperative Details

Exposure is obtained through a median sternotomy. The aortopulmonary window should be directly visible. The aorta is cannulated as distally as possible. A single right atrial cannula or, if an atrial septal defect (ASD) or ventricular septal defect (VSD) is present, separate caval cannulae must be used.

Cardiopulmonary bypass is instituted, and the procedure is performed at moderate hypothermia. One of the pulmonary arteries can be snared early in the operation if pulmonary overcirculation remains a problem or has been exacerbated by the induction of general anesthesia. Deep hypothermic circulatory arrest (DHCA) may be necessary if the lesion is complex or extends distally into the arch of the aorta. This also applies to patients who require repair of an interrupted aortic arch. Alternatively, repair of the interrupted aortic arch and aortopulmonary window can be performed using antegrade cerebral perfusion and limiting the period of circulatory arrest.[4]

The right and left pulmonary arteries should be snared upon initiation of cardiopulmonary bypass and before the administration of cardioplegia. The snares should be tightened to ensure good coronary flow and prevent runoff of cardioplegia into the pulmonary circulation. Consideration can be given to retrograde cardioplegia but is not mandatory. If DHCA is used for complex repairs, retrograde cardioplegia should not be necessary.

The defect is entered from the anterior aspect of the aorta, the main pulmonary artery, or the aortopulmonary window itself. The origins of the coronary arteries and branch pulmonary arteries are identified. A running nonabsorbable suture is then used to affix a patch of glutaraldehyde-treated pericardium or synthetic material to the posterior aspect of the defect. The remainder of the patch is then sewn to the superior and inferior aspects of the defects, with attention to the coronary arteries and branch pulmonary artery orifices.[7] The anterior aspect of the patch is incorporated into the closure of the incision.

Associated anomalies require repair using the protocols for those lesions. Specifically, the interrupted aortic arch is reconstructed before closure of the aortopulmonary window. Because of the presence of the aortopulmonary window, a single aortic cannula can be used. The patient is then cooled to 18°C (64.4°F). The head vessels and branch pulmonary arteries are snared, and cardioplegia is delivered into the coronary arteries. The descending aorta can then be anastomosed to a separate aortotomy above the aortopulmonary window or incorporated into an extension of the incision used to open the aortopulmonary window. The aortopulmonary window is then closed using patch material. The frequent abnormal right pulmonary artery must be baffled to be continuous with the main pulmonary artery.

The repair of Berry syndrome is more complex and may require a variety of techniques, including an intra-aortic patch, excision of the right pulmonary artery with a cuff of aorta that is used to reconstruct the anterior wall of the right pulmonary artery as well as reanastomosis of the transected aorta, and direct reimplantation of the right pulmonary artery into the main pulmonary artery.[10] In a rare case of preoperative airway compression anterior translocation of the right pulmonary artery has been utilized with a good result at 37 months of follow-up.[11]

The patient is then warmed and weaned from cardiopulmonary bypass. The integrity of the repair is examined by means of transesophageal echocardiography. Protamine is administered to reverse the heparin, and the patient is decannulated and the incision closed.

Postoperative Details

Inotropic support with milrinone, epinephrine, dopamine, or other agents can be anticipated in the initial postoperative period. A patient can usually be weaned off these over the next several hours and days, depending on his or her preoperative condition, length of time on cardiopulmonary bypass, and duration of hypothermic circulatory arrest.

Older patients may require treatment of postoperative pulmonary hypertension and pulmonary hypertensive crises. High levels of inspired oxygen remain one of the most effective pulmonary vasodilators. Deep sedation and paralysis are also effective in preventing hypertensive crises. If paralysis is not used, additional sedation should be used for endotracheal suctioning and other procedures. Inhaled nitric oxide may be effective for the treatment of pulmonary hypertension in intubated patients.

Patients may also require continued digitalis and furosemide, which may be discontinued in outpatient therapy.

Follow-up

Patients require follow-up with their cardiac surgeon initially and a pediatric cardiologist indefinitely. The surgical repair can be monitored by means of serial echocardiography. Further operative intervention may be required for the development of pulmonary artery stenosis. Some element of heart failure may persist after surgery and require continued medical therapy.

Complications

Pulmonary hypertensive crises may occur in the postoperative period. Patients at high risk should be sedated overnight, and paralysis should be considered. Acidosis should be avoided, and the pCO2 should be maintained at 30-35 mm Hg. Hypoxia should be avoided. Deep sedation should be confirmed before endotracheal suctioning. Finally, inhaled nitric oxide should be instituted for pulmonary artery pressures not managed by the above measures. Milrinone may also be used to lower pulmonary artery pressures and provide inotropic support. These measures can often be discontinued the next day.

Long-term follow-up is done with echocardiography. Recurrent coarctation and development of branch pulmonary artery stenosis are long-term risks.

Outcome and Prognosis

Outcomes continue to improve with better management during the perioperative period. An example of this can be seen in Backer and Mavroudis' description of their 40-year experience at Northwestern University.[3] Early in their experience, repair primarily consisted of aortopulmonary window (APW) division and resulted in a 37% mortality rate (6 of 16 patients). However, no deaths occurred in their most recent series of 6 patients in which cardiopulmonary bypass and transaortic patch closure were used. Most series consistently report a mortality rate less than 10%. The mortality rate for simple aortopulmonary window without other associated anomalies should be near 0%.[12]

The prognosis of aortopulmonary window is excellent if repaired in infancy and preferably before the onset of significant pulmonary hypertension. In Backer and Mavroudis' series noted above, the average pulmonary vascular resistance was elevated at 5.4 U/m2, but only one patient died from complications of pulmonary hypertension.

Future and Controversies

Little change has occurred in the diagnosis and management of aortopulmonary window (APW). Its frequent complexity and proximity to the aortic and pulmonary valves make catheter-based interventions unlikely, although a catheter-based device has been used to close a residual defect following surgical repair, and simple defects have been successfully closed.[13, 9] In addition, angioplasty with or without stenting may be effective in postoperative pulmonary artery stenoses.

Imaging modalities may advance and come to include MRI to better define the more complex lesions and avoid cardiac catheterization when the anatomy is unclear.