Definition
Aortopulmonary window (APW) is a congenital cardiovascular malformation in which there is side-to-side continuity of the lumens of the ascending aorta and pulmonary trunk in association with separate aortic and pulmonary valves or their atretic remnants.
This malformation has also been termed aortic septal defect, aortopulmonary fistula, aorticopulmonary fenestration, aorticopulmonary septal defect, or aorticopulmonary window.
Historical note
The first report of an APW was by Elliotson in 1830 and in the American literature by Cotton about 70 years later. , The first reported correct clinical diagnoses are attributed to Dodds and Hoyle in 1949 and to Gasul and colleagues in 1951. ,
In 1952, Gross reported successful ligation of an APW using a closed technique. Scott and Sabiston in 1953 and Fletcher and colleagues in 1954 reported successful division of an APW by a closed technique. , The operation was difficult and hazardous, however.
The advent of open heart operations with cardiopulmonary bypass (CPB) in 1954 to 1955 made it easier to correct this malformation. Division of the connection between aorta and pulmonary trunk was used in early cases at the Mayo Clinic. In 1957, Cooley and colleagues reported three successful repairs using this method. Bjork advised closure of the defect by the simple method of patching it from within the pulmonary trunk (Bjork VO: 1964, personal communication). This was later also suggested by Putnam and Gross. In 1968, Wright and colleagues reported the transaortic approach to intraluminal closure by direct suture. A year later, Deverall and colleagues reported use of a transaortic approach, but with polyester patch closure.
Johansson and colleagues described a “sandwich”-type closure in 1978. Schmid and colleagues closed APW without CPB using a felt strip technique. Richardson and colleagues used a contoured polyester patch, and Kitagawa and colleagues rerouted the pulmonary trunk for distal APW defects. , Messmer closed the defect using a pulmonary trunk flap and closed the pulmonary trunk with a pericardial patch. Di Bella and Gladstone used only a pulmonary trunk flap to close the defect. Kawata and colleagues closed an APW using a vascular clip in an infant weighing 758 g.
Morphology
An APW is usually a large defect between the aorta and pulmonary trunk, although in about 10% of patients the defect is small. The pulmonary arteries are normally related to the pulmonary trunk. As the term window implies, there is little or no length to the communication in most patients. It is nearly always a single orifice, although it may be fenestrated.
Several classifications have been proposed to describe the location of the anomalous “window” on the ascending aorta and its relationship to the branch pulmonary arteries. Mori and colleagues proposed the terms proximal, distal, and total to describe the location within the ascending aorta ; Richardson and colleagues used the term type I to describe proximal defects and type II to indicate defects in the distal ascending aorta. Ho and colleagues added the term intermediate to describe defects with upper and lower edges suitable for percutaneous closure. Jacobs and colleagues from the Society of Thoracic Surgeons’ Congenital Heart Surgery Database Committee recommended the terms type I–proximal defect, type II–distal defect, type III–total defect, and intermediate defect ( Fig. 41.1 ).
Classification scheme recommended by Society of Thoracic Surgeons’ Congenital Heart Surgery Database Committee for aortopulmonary window. Type I is a proximal defect located just above sinus of Valsalva, a few millimeters above semilunar valve. Proximal defects have little inferior rim separating defect from semilunar valves. Type II is a distal defect located in uppermost portion of ascending aorta. It corresponds to Richardson type II lesion, where defect overlies a portion of right pulmonary artery. Distal defects are noted to have a well-formed inferior rim but little superior rim. Type III is a total defect involving majority of ascending aorta. Type IV is the intermediate defect; these have adequate superior and inferior rims and are the group most suitable for possible device closure.
Proximal (type I) APWs are located in the proximal ascending aorta (see Fig. 41.1 ). The window is in the left lateral wall of the ascending aorta, usually close to the orifice of the left coronary artery, and in the contiguous right wall of the pulmonary trunk inferior to the origin of the right pulmonary artery (RPA). It is not surprising, therefore, that occasionally the right coronary artery, and rarely the left, may be transposed onto the pulmonary trunk close to the edge of the defect. This must always be considered in the surgical treatment of APW. When viewed from within the pulmonary trunk, the APW can be confused with the orifice of the RPA. The proximal type occurs in about 90% of APW cases.
Rarely, the opening between the aorta and the origin of the RPA from the pulmonary trunk is more downstream in the ascending aorta ( distal or type II APW ). , , The orifice may lie between the aorta and RPA; such defects have a spiral opening. , ,
In rare instances, the APW may involve nearly the entire ascending aorta ( total or type III ).
When the communication is such that the RPA takes its origin from the ascending aorta and is not related to the pulmonary trunk, the defect is called anomalous origin of the right pulmonary artery from the ascending aorta (see Chapter 42 ).
Because of the association between APW (particularly distally located ones) and anomalous origin of the RPA from the ascending aorta, the APW may open between the RPA and aorta. , The RPA may straddle the APW (“unroofing” of the RPA) or may originate completely from the aorta while maintaining continuity with the left pulmonary artery by way of the APW. Finally, the two conditions may simply coexist.
APW is accompanied by other cardiac anomalies in about 50% of cases, , of which interrupted aortic arch (IAA) (about 90% of which are type A and the rest type B) is the most frequently observed major associated lesion , (although this combination is rare among all patients with congenital heart disease). Other major associated lesions include ventricular septal defect (VSD), tetralogy of Fallot, double outlet right ventricle, transposition of the great arteries anomalous origin of a coronary artery, aortic isthmic hypoplasia, and subaortic stenosis. ,
Rarely, there is a complex syndrome of the APW, usually in the downstream portion of the ascending aorta, with aortic origin of the RPA, intact ventricular septum, patent ductus arteriosus (PDA), and IAA or severe coarctation (Berry syndrome) ( Fig. 41.2 ). This is a particularly lethal combination; most affected infants die shortly after birth.
Morphologic subtype of aortopulmonary window and anomalous origin of right pulmonary artery from ascending aorta with interrupted aortic arch (Berry syndrome).
From 5% to 10% of patients with the malformation have less severe associated cardiac anomalies such as right aortic arch (7%), ostium secundum atrial septal defects, or PDA. , , ,
The rarity of IAA with APW is such that among 472 neonatal patients with IAA reported in a Congenital Heart Surgeon’s Society study, 20 (4%) had IAA with APW. The morphologic subtypes of APW when associated with IAA are illustrated in Fig. 41.3 .
Morphologic subtypes of aortopulmonary window in interrupted aortic arch.
Clinical features and diagnostic criteria
In infants with isolated APW, symptoms and signs of heart failure usually develop early in life, and their presentation is similar to that of infants with a large VSD. These infants are generally small, underdeveloped, and tachypneic, and they tend to have recurrent respiratory infections.
On examination, the left precordium is prominent because of marked cardiomegaly. The second heart sound at the base is usually accentuated. The murmur is usually only systolic and of variable intensity. , , In about 15% of patients, it is continuous because the APW is smaller and pulmonary hypertension less than usual. , When the left-to-right shunt through the defect is large, there are peripheral signs of rapid aortic runoff, clinically mimicking large PDA or aortic insufficiency (e.g., jerky or collapsing peripheral pulses). These signs are not evident when heart failure is marked or pulmonary vascular resistance is severely elevated.
Chest radiograph and electrocardiogram (ECG) findings are similar to those of infants and young children with VSD or large PDA, giving evidence of left and right ventricular enlargement and large pulmonary blood flow. Left atrial enlargement (a result of large pulmonary blood flow) is usually prominent.
Differential diagnoses before special study include large PDA (see Chapter 28 ), truncus arteriosus (see Chapter 43 ), and, in patients beyond the infant age group, VSD with aortic regurgitation (see Section II of Chapter 33 ) and ruptured sinus of Valsalva aneurysm (see Chapter 37 ).
Since the early 1990s, diagnosis has relied exclusively on two-dimensional (2D) echocardiography. , Nevertheless, other imaging techniques are useful. Garver and colleagues correlated echocardiography, angiography, and magnetic resonance imaging (MRI) to achieve accurate diagnosis in APW. Prior to the advent of 2D echocardiography, cardiac catheterization and cineangiography were used to provide the definitive diagnosis and identify associated cardiac anomalies. Multidetector computed tomography (MSCT) is a noninvasive investigation that is gaining popularity to assess complex lesions associated with APW. On the basis of computed tomography (CT) images, 3D reconstruction can be performed to create 3D models. This will allow better understanding of the spatial relationship between the cardiac and vascular structures to aid in corrective surgery.
Natural history
APW is a rare malformation, occurring in about 0.2% of cases of congenital heart disease. , , , There is no known tendency for APWs to close spontaneously. The natural history of infants with large APWs is at least as unfavorable as that of infants with persistently large VSD (see “ Natural History ” in Section I of Chapter 33 ). In the absence of surgical correction, mortality in the first year of life has been estimated at 40%. In fact, patients with large APWs are rarely seen in childhood or adult life, and those who survive beyond early life have important pulmonary vascular disease. This natural history is, therefore, similar to that of surgically untreated older patients with large VSD.
Technique of operation
Because APW often coexists with other important cardiac anomalies, the basic technique of repair must be modified and adapted to the individual situation. However, every effort should be made to accomplish a one-stage repair. A special combination is APW and anomalous origin of the RPA from the ascending aorta, in which the defect in the pulmonary trunk of the APW may be left open anatomically but functionally closed by connecting it to the orifice of the RPA by one of several techniques. , , , The aortic end of the APW is patch closed.
The following discussion pertains specifically to isolated APWs . At operation, the diagnosis can usually be confirmed from outside the heart. The first portion of the aorta and pulmonary trunk form a large confluence that suggests truncus arteriosus. However, separate semilunar valve “annuli” can usually be suspected by finding a dimple between the two great arteries where they arise from the heart. Intraoperative inspection from outside the heart also confirms the position of the coronary arteries and the RPA.
The operation may be done with CPB (see Section III of Chapter 2 ) unless the infant weighs less than about 2.5 kg, in which case hypothermic circulatory arrest may be used (see Section IV of Chapter 2 ). Particular care must be taken in selecting the site for aortic cannulation, which must be as far downstream as possible. Also, before establishing CPB, a limited dissection is made between the aorta and pulmonary trunk, downstream from the APW but proximal to the aortic cannulation site. More extensive dissection should be avoided due to the risk of serious bleeding.
Care is taken to identify and protect the RPA during this dissection and while placing the aortic clamp. A single venous cannula may be used, or the cavae may be cannulated directly. The right atrium is opened and a vent or pump sucker is placed across the foramen ovale or through the right superior pulmonary vein into the left atrium.
As soon as CPB has been initiated and core cooling begun, separate tourniquets may be placed on left and right pulmonary arteries; alternatively, a side-biting clamp (e.g., small Cooley clamp) is placed across the window from the pulmonary trunk side to occlude the window. The aortic occlusion clamp is positioned exactly at the place provided by the prior dissection. Cold cardioplegic solution is injected into the ascending aorta or retrogradely via the coronary sinus (see “ Methods of Myocardial Management during Cardiac Surgery ” in Chapter 3 ).
Access to the defect can be through the aorta, through the pulmonary trunk or directly through APW. Whatever the access, it is mandatory to determine its size and location of defects, relation to the semilunar valves, the origin of the RPA, and the ostium of the two coronary arteries.
Currently, the most common technique is by vertical incision made at the anterior wall of the APW itself, more or less transecting its anterior half ( Fig. 41.4 A). After carefully identifying orifices of the RPA and left coronary artery, the patch for closure is sutured to the posterior, superior, and inferior walls of the window ( Fig. 41.4 B). The incision at the site of the window is then closed by incorporating the front edge of the patch, with each stitch passing through the aortic wall, the patch, and the pulmonary trunk wall ( Fig. 41.4 C). This technique allows visualization of the left coronary ostium and orifice of the RPA and provides a secure partitioning of the ascending aorta from the pulmonary trunk. Unless there is aneurysmal thinning around the window, this technique seems useful. The most frequently used patches are 0.4 mm polytetrafluoroethylene (PTFE) or glutaraldehyde processed autologous pericardium (20-30 min). PTFE patch has an advantage because it is meant to divide two compartments with very different pressure—the aorta and the pulmonary artery. This technique is often referred to as “sandwich technique” although the authors do not define it as such.
Repair of aortopulmonary window using the “sandwich technique.” (A) An incision is made on the window itself. (B) A patch material is sutured onto the posterior, superior and inferior borders of the window. (C) Closing sutures anteriorly that incorporate the patch.
In repair of the type I APW access is directly through the aortic wall. Incision can be transverse at the level of APW or vertical from the aortic valve to the aortic cross-clamp, when additional clarification of the origin of RPA is needed ( Fig. 41.5 A). The patch for closure of the window must be positioned so that both coronary ostia are on the aortic side of the patch. Small-sized APWs may be closed by direct suture, using one or two rows of continuous 4-0 polypropylene sutures, but a patch is generally advisable even for smaller defects ( Fig. 41.5 B). The aortotomy incision is then closed with one row of continuous polypropylene sutures. The remainder of the operation, including the de-airing procedure, is carried out as usual (see “ De-airing the Heart ” in Section III of Chapter 2 ).
Repair of type I aortopulmonary window (APW). (A) Operation is performed on cardiopulmonary bypass with aorta occluded. APW is exposed through a transverse aortotomy. It is located just above sinutubular junction. Origin of left coronary artery is identified because it may have a close relationship with inferior margin of APW. (B) APW is closed with a polyester, polytetrafluoroethylene, or pericardial patch to create a partition between aorta and pulmonary trunk. Left coronary artery is protected from inclusion in suture line.
If the APW involves the front wall of the proximal RPA (type II), approach is made through a vertical or transverse aortotomy ( Fig. 41.6 A) and the defect closed with a patch that extends out along the RPA ( Fig. 41.6 B).
Repair of type II aortopulmonary window (APW). (A) Operation is performed on cardiopulmonary bypass. Aortic perfusion cannula is placed in aortic arch to allow occlusion of aorta near origin of brachiocephalic artery. APW is exposed through a transverse aortotomy. It is located on posterior aspect of aorta and involves the pulmonary trunk at origin of right pulmonary artery. (B) Partition between aorta and pulmonary trunk is created using a polyester patch. There must be some contour to the patch to avoid stenosis of proximal right pulmonary artery. Edge of aorta at right side of window must be identified and the patch attached to aortic edge to prevent communication of aorta with right pulmonary artery.
