Aortopulmonary Window

Definition

Aortopulmonary window (APW) is a round, oval, or sometimes spiral opening between the ascending aorta and pulmonary trunk, occurring as a congenital anomaly in hearts with separate aortic and pulmonary valves. This malformation has also been termed aortic septal defect; aortopulmonary fistula, fenestration, or septal defect; and aorticopulmonary window, fistula, fenestration, or septal defect.

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 operation 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. 44-1 ).

Proximal (type I) APWs are located in the proximal ascending aorta (see Fig. 44-1 ). 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. 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 right pulmonary artery. The proximal type occurs in about 90% of APW cases.

Rarely, the opening between the aorta and the origin of the right pulmonary artery from the pulmonary trunk is more downstream in the ascending aorta ( distal or type II APW ). The orifice may lie between the aorta and right pulmonary artery; 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 right pulmonary artery 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 45 ).

Because of the association between APW (particularly distally located ones) and anomalous origin of the right pulmonary artery from the ascending aorta, the APW may open between the right pulmonary artery and aorta. The right pulmonary artery may straddle the APW (“unroofing” of the right pulmonary artery) 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, transposition of the great arteries (Vannini V: personal communication, 1980), 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 right pulmonary artery, intact ventricular septum, patent ductus arteriosus, and interrupted aortic arch or severe coarctation (Berry syndrome). This is a particularly lethal combination; most affected infants die shortly after birth.

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 patent ductus arteriosus.

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 ( Fig. 44-2 ).

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 repeated 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 (e.g., jerky or collapsing peripheral pulses), but 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 patent ductus arteriosus, 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 patent ductus arteriosus (see Chapter 37 ), truncus arteriosus (see Chapter 43 ), and, in patients beyond the infant age group, VSD with aortic regurgitation (see Section II of Chapter 35 ) and ruptured sinus of Valsalva aneurysm (see Chapter 36 ).

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. Cardiac catheterization shows blood oxygen saturation in the pulmonary artery is elevated over that in the right ventricle and right atrium in most cases. Occasionally, oxygen saturation in the right ventricle is increased over that in the right atrium, which may suggest VSD or truncus arteriosus until cineangiography shows this to be from pulmonary valve regurgitation associated with APW. Ascending aortic angiography shows rapid filling of the pulmonary trunk through the APW, as well as separate aortic and pulmonary valves. Because location of the APW varies and coronary arteries may arise from the pulmonary trunk, visualization of all anomalies must be accurate.

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 35 ). 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 right pulmonary artery from the ascending aorta, in which the APW may be left open anatomically but functionally closed by connecting it to the orifice of the right pulmonary artery by one of several techniques. The discussion that follows pertains specifically to isolated APWs .

Diagnosis can usually be verified at operation 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 “anuli” can usually be verified by finding a dimple between the two great arteries where they arise from the heart. Even in young infants, the left ventricle is enlarged, usually about grade 3 on a scale of 0 to 6, as are the left atrium and right ventricle. In older children, ventricular enlargement and hypertrophy are severe.

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. Care is taken to identify and protect the right pulmonary artery 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 pump-oxygenator sump sucker placed across the foramen ovale into the left atrium.

As soon as CPB has been initiated and core cooling begun, a side-biting clamp (e.g., small Cooley clamp) is placed across the window from the pulmonary trunk side to occlude the window; alternatively, separate tourniquets may be placed on left and right pulmonary arteries. 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 ).

Repair can be done through either the aorta or pulmonary trunk, and even the older technique of complete division has given good results. However, an initial approach through the aorta is generally recommended to facilitate clear identification of the aortic valve and right and left coronary orifices in relation to the defect. The aorta is opened transversely at the level of the APW ( Fig. 44-3, A ). Both coronary arteries must be identified. If one is anomalously positioned in the pulmonary trunk, the patch for closure of the window must be positioned so that both coronary ostia are on the aortic side of the patch. Small or moderate-sized APWs may be closed by direct suture, using one or two rows of continuous 4-0 polypropylene sutures. A large window is closed with a polyester, polytetrafluoroethylene (PTFE), or pericardial patch sewn into place with continuous 4-0 or 5-0 polypropylene sutures ( Fig. 44-3, 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 ).

If the APW involves the front wall of the proximal right pulmonary artery (type II), approach is made through a vertical or transverse aortotomy ( Fig. 44-4, A ) and the defect closed with a patch that extends out along the right pulmonary artery ( Fig. 44-4, B ).

Alternatively, a vertical incision may be made in the anterior wall of the APW itself, more or less transecting its anterior half. After carefully identifying orifices of the right pulmonary artery and left coronary artery, the patch for closure is sutured to the posterior, superior, and inferior walls of the window. The incision into 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. This technique allows visualization of the left coronary ostium and orifice of the right pulmonary artery 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.

A modification of this technique is required when the right coronary artery arises from the pulmonary trunk just to the left of the anterior wall of the APW. Then the anterior incision into the window curves to the left into the pulmonary trunk to create a flap of anterior pulmonary trunk wall that includes the origin of the right coronary artery. The flap should be large enough to cover the entire window. It is sewn into position over the window with a continuous polypropylene stitch. Repair is completed by closing the defect in the pulmonary trunk with a pericardial patch.

Rarely, the right coronary artery arises from the anterior aspect of the pulmonary trunk at some distance from the APW. In that situation, the right coronary artery can be taken as a button from the pulmonary trunk, mobilized, and reimplanted into the aorta at a site distinct from the APW, which is closed with a separate patch. Similar methods (flap reconstruction or reimplantation) can be used to repair APW with an anomalous origin of the left coronary artery from the posterior wall of the pulmonary trunk.

Special Features Of Postoperative Care

Postoperative care is as usual (see Chapter 5 ). The hemodynamic state is generally excellent because the left ventricle is large, no ventriculotomy has been made, and duration of myocardial ischemia is less than 1 hour. When repair has been performed in a neonate or infant, care appropriate to this age group is used (see Section IV, Chapter 5 ).

Results