You are in: eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiothoracic Surgery Aortopulmonary Window: Surgical PerspectiveArticle Last Updated: Jul 7, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Mary C Mancini, MD, PhD, Director of Cardiothoracic Transplantation, Professor, Department of Surgery, Louisiana State University Health Sciences Center Mary C Mancini is a member of the following medical societies: American Heart Association, American Medical Association, American Thoracic Society, Association for Academic Surgery, Association for Surgical Education, International College of Surgeons, International Society for Heart and Lung Transplantation, New York Academy of Sciences, Phi Beta Kappa, and Southern Thoracic Surgical Association Coauthor(s): Jeff L Myers, MD, PhD Chief, Pediatric and Congenital Cardiac Surgery, Department of Surgery, Massachusetts General Hospital; Associate Professor of Surgery, Harvard Medical School; Hani A Hennein, MD, FACS, FAAP, FCCP, Associate Professor of Surgery and Pediatrics, Case Western Reserve University School of Medicine; Chief, Section of Pediatric Cardiothoracic Surgery, Department of Surgery, University Hospitals of Cleveland, Rainbow Babies and Childrens Hospital Editors: Daniel S Schwartz, MD, FACS, Clinical Assistant Professor of Cardiothoracic Surgery, New York University School of Medicine; Consulting Staff, Department of Surgery, Division of Thoracic Surgery, North Shore University Hospital/Long Island Jewish Medical Center; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Robert DB Jaquiss, MD, Assistant Professor of Surgery, Division of Cardiothoracic Surgery, Department of Surgery, Medical College of Wisconsin; Consulting Surgeon, Children's Hospital of Wisconsin; Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine; John Kupferschmid, MD, Director of Congenital Heart Surgery, Department of Surgery, Methodist Children's Hospital at San Antonio Author and Editor Disclosure Synonyms and related keywords: aortopulmonary window, aortopulmonary septal defect, APW, pulmonary vascular resistance, PVR, pulmonary artery, aorta, Eisenmenger syndrome, pulmonary circulation, distal arch obstruction, interrupted aortic arch, progressive left ventricular dysfunction, congestive heart failure, cardiac catheterization, pulmonary vascular hypertension, patent ductus arteriosus, atrial septal defect, ASD, tetralogy of Fallot, deep hypothermic circulatory arrest, DHCA, cardioplegia INTRODUCTIONSection 2 of 11
  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. History of the ProcedureAPW 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. Subsequent development of cardiopulmonary bypass techniques simplified the repair. Currently, an incision directly into the APW or the aorta is used. Most lesions are repaired by direct patch repair of the defect. ProblemAPW 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. APW is frequently associated with other cardiac defects that affect outcome and complicate repair. FrequencyAPW 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 1 case per year. EtiologyAPW represents a failure of the conotruncus to differentiate into the aorta and pulmonary artery. No genetic associations or environmental risk factors are known. The 2 competing embryologic theories are (1) that APW is part of a spectrum of conotruncal abnormalities, which includes truncus arteriosus at one end of the spectrum, and (2) that APW is unrelated to truncus arteriosus because the lesions associated with each defect are so dissimilar. PathophysiologyThe hemodynamic abnormalities are similar to those seen with a large, unrestrictive ventricular septal defect (VSD) or patent ductus arteriosus. APW 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 APW acts as an obstruction to systemic flow and further increases the left-to-right shunt. Perfusion to the lower body is therefore dependent 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. ClinicalThe presentation is dependent 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. For excellent patient education resources, visit eMedicine's Circulatory Problems Center and Heart Center. Also, see eMedicine's patient education articles Aortic Aneurysm and Congestive Heart Failure. INDICATIONSSection 3 of 11
The presence of an 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 ANATOMYSection 4 of 11
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. Further distal extension is associated with interrupted aortic arch (usually type A) and patent ductus arteriosus. More than half of patients with APW have additional associated lesions. They range from patent ductus arteriosus and atrial septal defect (ASD) to interrupted aortic arch and tetralogy of Fallot. 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. CONTRAINDICATIONSSection 5 of 11
The primary contraindications to surgery are similar to those in a patient with a large 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. WORKUPSection 6 of 11
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Diagnostic Procedures
TREATMENTSection 7 of 11
Medical therapyMedical therapy is focused on preoperative stabilization. Surgical correction is the only effective treatment for APW. 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 therapySurgery is the treatment for APW. 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 APW 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 detailsPreoperative care is centered on correction of acidosis and stabilization of the child. Congestive heart failure symptoms are treated with digoxin, Lasix, 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 may be required. Patients presenting when older than 6 months need cardiac catheterization to rule out irreversible pulmonary hypertension. Intraoperative detailsExposure is obtained through a median sternotomy. The APW should be directly visible. The aorta is cannulated as distally as possible. A single right atrial cannula or, if an ASD or 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. The right and left pulmonary arteries should be snared 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 it 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 APW 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. 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 APW. Because of the presence of the APW, 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 APW or incorporated into an extension of the incision used to open the APW. The APW is then closed using patch material. The frequent abnormal right pulmonary artery must be baffled to be continuous with the main pulmonary artery. 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 detailsInotropic 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 Lasix, which may be discontinued in outpatient therapy. Follow-upPatients 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. COMPLICATIONSSection 8 of 11
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 PROGNOSISSection 9 of 11
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. Early in their experience, repair primarily consisted of 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 APW without other associated anomalies should be near 0%. The prognosis of APW 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 CONTROVERSIESSection 10 of 11
Little change has occurred in the diagnosis and management of APW. Its frequent complexity and proximity to the aortic and pulmonary valves make catheter-based interventions unlikely in the future, although a catheter-based device has been used to close a residual defect following surgical repair. 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. REFERENCESSection 11 of 11
Aortopulmonary Window: Surgical Perspective excerpt Article Last Updated: Jul 7, 2006 |
