Origin of the right or left pulmonary artery from the ascending aorta

Definition

Anomalous origin of a pulmonary artery from the ascending aorta is a congenital cardiovascular malformation in which one branch pulmonary artery arises from the ascending aorta and the other branch pulmonary artery arises from the pulmonary trunk.

Usually the right pulmonary artery (RPA) or rarely, the left pulmonary artery (LPA), arises from the ascending aorta in the presence of separate aortic and pulmonary valves and without interposition of ductal tissue. While there are some similarities to hemitruncus (see Truncus Arteriosus discussion, Chapter 43 ), this is a distinct entity defined by two separate semilunar valves (unlike hemitruncus) and intrapericardial aortic origin of one pulmonary artery. By definition, the pulmonary arteries are discontinuous, as the remaining pulmonary artery arises from the right ventricle. Rarely, both right and left pulmonary arteries arise from the ascending aorta in the presence of two separate semilunar valves.

Origins of one or both pulmonary arteries from the transverse aortic arch via a ductus arteriosus or collateral arteries and from the descending thoracic aorta via collateral arteries are not discussed; these conditions are most commonly part of tetralogy of Fallot, but they can occur in the presence of other intracardiac defects or even with normal intracardiac morphology (see Chapters 34 and 35 ). When both the RPA and LPA or only one pulmonary artery arise from the ascending aorta with a common semilunar valve, the condition is a subset of truncus arteriosus (see Chapter 43 ).

Historical note

The first description of this entity was by Fraentzel, who in 1868 reported the case of a 25-year-old woman dying in heart failure, with the RPA arising from the ascending aorta and an aortopulmonary window. In 1914, Doering reported aortic origin of the RPA in an infant dying at age 8 months whose only associated anomaly was a patent ductus arteriosus. Bopp, in 1949, gave a detailed report of this condition ; since then, and with development of cardiac catheterization and angiography, other cases have been reported.

In 1957, Caro and colleagues corrected the malformation by disconnecting the RPA from the ascending aorta and connecting it with an interposition graft to the pulmonary trunk. The patient, a 23-year-old man, died a short time after the operation. The first successful repair, which was in a 12-month-old infant, was reported in 1961 by Armer and colleagues. They interposed a graft between the pulmonary trunk and distal end of the divided RPA and closed a coexisting patent ductus arteriosus. In 1967, Kirkpatrick and colleagues reported the first successful cases of retroaortic direct anastomosis of the divided RPA to the pulmonary trunk. The first report of successful surgical treatment of aortic origin of the LPA, in a 6-week-old infant, was by Herbert and colleagues in 1973.

Morphogenesis and morphology

Morphogenesis

Anomalous origin of the RPA from the ascending aorta is related to development of the aortopulmonary septum by fusion of the right and left conotruncal ridges. As such, this defect has developmental morphogenesis similar to aortopulmonary window (see Chapter 41 ). Severe unequal partitioning of the aortopulmonary trunk by conotruncal ridges results in more dorsal development of the aorta. While other potential origins have been proposed, eccentric growth of the dorsal wall of the aortic sac and the impact of the aortopulmonary septum appear most plausible, and has been detailed by Anderson and colleagues. In the situation of anomalous aortic origin of the RPA, the right sixth aortic arch originates solely from the ascending aorta and is not related to the pulmonary trunk. The result of severe conotruncal ridge malalignment is anomalous origin of the RPA from the ascending aorta.

Morphology

Anomalous origin of right pulmonary artery.

The RPA usually arises from the right or posterior aspect of the ascending aorta ( Fig. 42.1 ) in this condition, but occasionally it arises from the leftward posterior aspect. Its origin is usually within 1 to 3 cm of the aortic valve. Uncommonly, it arises from the distal portion of the ascending aorta just proximal to the origin of the brachiocephalic artery. The RPA origin is rarely stenosed, and the vessel is usually as large as or larger than the normally connected LPA; it is normal in structure, course, and distribution. ^,

An illustration shows the right pulmonary artery arising from the ascending aorta. The illustration shows three labeled vessels. The aorta is drawn as a large central structure with an upward course. The pulmonary trunk is drawn to the right side as a large curved vessel connected near the lower part of the aorta. The right pulmonary artery is drawn as a smaller vessel that extends horizontally from the side of the ascending aorta. A narrow shaded region marks the connection between the right pulmonary artery and the ascending aorta. — • Figure 42.1

When the RPA arises anomalously from the ascending aorta and no other anomalies are present, pulmonary vascular beds of the two lungs may be similar despite differences in origin of the pulmonary arteries. ^, Occasionally, pulmonary and tricuspid valves are dilated as a result of right heart failure, and the tricuspid leaflets may be thickened and edges rolled. Origin of the RPA from the ascending aorta is an isolated lesion in about 20% of cases. ^, In the remainder, the most common coexisting lesion is patent ductus arteriosus, present in about 50% of cases. ^,

Other less common associations are with tetralogy of Fallot, ventricular septal defect, aortopulmonary window, coarctation of the aorta, interrupted aortic arch, and atrial septal defect. ^, Severe contralateral (left) pulmonary vein stenosis may coexist. The vein stenoses are typically tubular, with dilation of the left pulmonary veins proximal to the stenoses. Also, Sievers and colleagues reported coexisting subtotal obstruction of the left pulmonary vein orifices by a membrane that was excised at operation.

Anomalous origin of left pulmonary artery.

Origin of the LPA from the ascending aorta is rare. The majority of the time it is accompanied by an associated defect (87% in the recent meta-analysis by Loomba and colleagues ). Tetralogy of Fallot was the most commonly associated anomaly at 52% and right aortic arch in approximately 70%. A patent ductus arteriosus was present in 14%, and it was right-sided in 88% of those. A number of other anomalies have been reported, including tetralogy of Fallot with absent pulmonary valve. The genetic diagnosis of 22q11 was confirmed in 7%.

Anomalous origin of both pulmonary arteries.

Origin of both RPA and LPA from the ascending aorta has been reported in one patient who had no other cardiac anomaly. The origin was by way of a short single trunk coming off the posterior aspect of the ascending aorta, with the pulmonary trunk arising normally from the right ventricle and connected only to a patent ductus arteriosus. Repair was attempted unsuccessfully at age 11 days.

Classification.

Several classification systems have been proposed but have not been widely adopted. Generally, the lesion is described by the sidedness of the involved pulmonary artery and any accompanying congenital heart disease. Nevertheless, it is worth noting two classification systems. Wenxiu and colleagues proposed a classification system based on the proximity of the origin of the anomalous pulmonary artery to the aortic valve, while Garg and colleagues developed a classification system that includes laterality of the pulmonary artery (right or left), proximity of origin to the aortic valve, as well as the presence or absence of right ventricular outflow tract obstruction.

Clinical features and diagnostic criteria

When the condition is isolated except for a patent ductus arteriosus, the patient characteristically presents early in infancy with respiratory distress and heart failure. ^, ^, ^, Frequently, the infant is acutely ill. In the absence of other significant congenital heart disease, the lung with the anomalous pulmonary artery will be exposed to both pressure and volume loading from an unrestricted shunt directly from the aorta. The patient will have pulmonary overcirculation with concomitant pulmonary edema that can lead to secondary hypoxia. There will be a large left to right shunt with associated heart failure signs and symptoms. There may be cyanosis from reversed shunting through a patent ductus arteriosus or a patent foramen ovale resulting from right heart failure.

There are no typical auscultatory findings, and murmurs may or may not be present. ^, ^, ^, ^, When present, the murmur is usually systolic and heard along the left sternal border. Rarely, it may be continuous as a result of kinking or stenosis of the artery. The peripheral pulses are jerky or bounding because of rapid runoff from the aorta into the lung and consequent left-to-right shunting. Electrocardiographic findings are not diagnostic and usually indicate biventricular and right atrial enlargement. Cardiomegaly is usually severe on the chest radiograph, with the heart assuming a globular shape. ^, Pulmonary plethora is usually of similar degree bilaterally. ^, ^,

When tetralogy of Fallot is present with severe pulmonary stenosis, clinical features are dominated by the physiology of tetralogy of Fallot. The condition may be suspected, however, because the lung supplied by the anomalously arising artery is usually plethoric, whereas the other lung is oligemic. ^, ^,

Since the early 1990s, diagnosis and assessment have been adequately made with two-dimensional echocardiography alone, making cardiac catheterization unnecessary ( Fig. 42.2 ). Echocardiography will also demonstrate elevated right ventricular pressures, and this anomaly should be in the differential for neonates and infants with pulmonary hypertension. This diagnosis may also be noted on fetal ultrasound and the diagnosis confirmed after birth.

A pair of suprasternal notch coronal echocardiographic scans shows the aorta, the right pulmonary artery, the left pulmonary artery, the brachiocephalic vein, and the left atrium. The pair of suprasternal notch coronal echocardiographic scans is shown side by side. The left scan labels the aorta in the center, the right pulmonary artery extending from it, the left pulmonary artery positioned laterally, the brachiocephalic vein located above the great vessels, and the left atrium located below. A vertical color scale is present on the left margin, and a horizontal wave trace is placed along the lower edge. The right scan also labels the aorta, the right pulmonary artery, the left pulmonary artery, the brachiocephalic vein, and the left atrium, and it includes Doppler color flow within the outlined region that shows flow entering the right pulmonary artery from the aorta. — • Figure 42.2

While used infrequently, cardiac catheterization and angiography may provide additional information. Pressure in the pulmonary artery arising from the aorta is systemic in almost all cases, because ostial stenosis is rare. As already noted, pressure in the pulmonary artery that arises normally is usually also elevated to systemic or suprasystemic levels. ^, Accurate measurement of pulmonary and systemic blood flows is difficult in this situation but not critical, because the infants usually present with clear clinical evidence of increased pulmonary blood flow. Pulmonary vascular resistance in the normally connected lung can be calculated and is a useful guide to assess operability; this evaluation is essential in older patients. Cineangiography is diagnostic, and a right ventriculogram or pulmonary angiogram opacifies only the normally connected pulmonary artery. Antegrade or retrograde aortography shows the pulmonary artery that arises from the ascending aorta ( Fig. 42.3 ). Cineangiography is also used to define other cardiac anomalies that may be present. ^,

An angiographic scan shows contrast filling the left ventricle, the ascending aorta, and the right pulmonary artery in an anteroposterior projection. — • Figure 42.3

In neonates and infants in whom catheterization is not critical, computed tomography angiography can confirm morphologic details suspected by echocardiography, and can also be useful for operative planning ( Fig. 42.4 ).

A computed tomography angiogram that shows the heart, the curved aorta, and a large vessel extending toward the right side in a sagittal oblique chest view. — • Figure 42.4

Natural history

Anomalous origin of a branch pulmonary artery from the ascending aorta is rare, reportedly accounting for 0.12% of all congenital heart defects. Nearly all cases involve the RPA. ^, As of 2004, 136 cases of RPA from the aorta had been reported, and from 2004 to 2010, at least 35 additional cases appeared in the literature. In 2003, Prifti and colleagues reviewed the reported experience with LPA from the aorta and found 77 cases; however, many of these appear to have had LPA origins from the descending thoracic aorta or from a ductus, with a high association with tetralogy of Fallot, and thus likely represent a different lesion. Without intervention, anomalous origin of the Pulmonary artery from the aorta is a lethal condition. About 70% of surgically untreated patients are dead by age 6 months and 80% by age 1 year (see Fig. 42.5 ). Intractable heart failure is the usual mode of death. However, rare case reports have been published describing adults surviving with this anomaly.

A graph shows a survival curve that plots the proportion surviving against age in months. The graph presents a continuous line with dashed boundary lines that plot age in months on the horizontal axis from 0 to 12 and proportion surviving on the vertical axis from 0.0 to 1.0. The main line starts near 1.0 at age 0, drops steeply through months 1 and 2, falls to about 0.45 by month 3, and continues to decline with smaller decreases across months 4 to 8. The line then levels near 0.18 from months 9 to 12. The dashed boundary lines run above and below the main line for all ages shown, following the same pattern and outlining the upper and lower bounds of the curve. — • Figure 42.5

Pulmonary hypertension in the anomalous pulmonary artery is uniformly present, and commonly it is also present in the normally connected pulmonary artery. This finding is supported by Pool and colleagues’ observation that pulmonary hypertension develops in 19% of infants born with unilateral absence of a pulmonary artery and no associated malformations, and that ligation of one pulmonary artery within 24 hours of birth in five calves resulted in severe pulmonary hypertension in the opposite lung within 2 months. Surprisingly, Keane and colleagues reported no important obstructive vascular changes in either lung in most patients dying in the first 6 months of life. This, however, does not mean that pulmonary hypertension was not present, but only that pathologic changes were not evident.

Among older patients with anomalous origin of the RPA, pathologic evidence of hypertensive pulmonary vascular disease is usually present, often to a similar extent in the two lungs, but interestingly sometimes greater in the right and sometimes greater in the left. It is likely that the natural history of isolated origin of the LPA from the ascending aorta is similar, but too few patients have been observed to establish this.

Technique of operation

Preparations for operation, median sternotomy, and cardiopulmonary bypass (CPB) are those normally used (see “ Preparation for Cardiopulmonary Bypass ” in Section III of Chapter 2 ), as are the techniques for myocardial management (see “ Cold Cardioplegia, Controlled Aortic Root Reperfusion, and [When Needed] Warm Cardioplegic Induction ” in Chapter 3 ). The technique described in this section is for anomalously arising RPA; it is similar when the LPA is affected. While CPB is used in the majority of surgical repair (87% in the meta-analysis by Agati and colleagues), bypass is not always necessary.

Once the pericardium has been opened, the anomalously originating RPA is visualized coming from either the posterior or right lateral aspect of the ascending aorta ( Fig. 42.6 A). It passes into the right hemithorax behind the superior vena cava. The aorta is completely dissected from the pulmonary trunk, and the ductus arteriosus is dissected out at this point.

A set of three illustrated surgical panels that show the aorta, pulmonary arteries, instruments, and steps for moving the right pulmonary artery. The set of three illustrations shows repair of anomalous origin of the right pulmonary artery from the ascending aorta across three labeled panels A, B, and C. Panel A shows the aorta in the center with surgical clamps near the upper portion, the left pulmonary artery extending upward and to the left, and the right pulmonary artery extending to the right, with written labels that state Aorta, Left pulmonary artery, Right pulmonary artery, and J RHEAD. while the right pulmonary artery is separated from the aorta, and instruments hold the tissues. Panel B shows the ascending aorta with an aortic patch held by surgical tools, the left pulmonary artery above the operative field, the pulmonary trunk beneath the patch, and the right side of the pulmonary trunk pulled toward the right, with the opening in the pulmonary trunk and labels for the aortic patch, the pulmonary trunk, the left pulmonary artery, and the right pulmonary artery. Panel C contains two diagrams, as the first shows the right pulmonary artery positioned for connection to the pulmonary trunk, and the second shows the completed continuous stitched anastomosis held by instruments with a label marking the right pulmonary artery anastomosis. A small inset on the right shows the final repair with the aorta at the top and both pulmonary arteries extending outward in restored continuity. — • Figure 42.6

The purse-string sutures and preparation for CPB are made as usual, except that care is taken to place the aortic cannula far enough downstream so that the aorta may be occluded distal to the aortic origin of the RPA (see Fig. 42.6 A). A single venous cannula is placed into the right atrium. CPB is established as usual, and as soon as it has begun, a temporary arterial clamp is placed across the RPA to avoid runoff.

The ligamentum arteriosum or ductus arteriosum is ligated and specifically divided. Division allows improved mobility of the pulmonary trunk so that the connection to the RPA can be performed with minimal tension. A vent catheter is placed in the left atrium through a purse-string in the right upper pulmonary vein. After the aorta is occluded well distal to the RPA, cold cardioplegia is administered. The clamp is removed from the RPA, which is then thoroughly mobilized beneath the superior vena cava out to the lobar branches.

The pulmonary artery is then disconnected from the ascending aorta (see Fig. 42.6 A). The defect left in the ascending aorta is closed by a pericardial patch or other patch material ( Fig. 42.6 B). In some cases, it may be possible to close the aorta transversely by direct suture. The aorta is rotated anteriorly and leftward. The right side of the pulmonary trunk is pulled out from beneath the aorta (see Fig. 42.6 B), and a longitudinal incision is made in it. An anastomosis is made between the end of the well-mobilized RPA and the side of the pulmonary trunk ( Fig. 42.6 C). A 7-0 polypropylene suture is used, sewing from within the vessels posteriorly and working external to the vessels anteriorly. The completed repair establishes continuity between the RPA and pulmonary trunk, eliminating the shunt ( Fig. 42.6 , inset ).

An alternative technique that achieves greater length on the RPA was described by van Son and Hanley ( Fig. 42.7 A). After the aorta is occluded, it is incised transversely at the level of RPA origin. The aortic incision is continued posteriorly, leaving a generous cuff of posterior wall around the origin of the RPA. Position of the left coronary artery is noted and its ostium protected from injury. An incision is made in the right lateral wall of the pulmonary trunk so as to create an anteriorly based flap ( Fig. 42.7 B). An anastomosis of the RPA to the pulmonary trunk is created with the two flaps forming the proximal segment of the RPA ( Fig. 42.7 C). The ascending aorta is reconstructed by end-to-end anastomosis ( Fig. 42.7 D).

A set of four illustrations that shows sequential surgical steps involving the aorta, the pulmonary trunk, the ductus arteriosus, and the right pulmonary artery. The set of four illustrations labeled A, B, C, and D shows a detailed surgical sequence in order. Illustration A shows the aorta at the center with multiple branching vessels, the ductus arteriosus positioned at the upper left, and the pulmonary trunk located above the aorta. The right pulmonary artery extends to the right. Several incision guides follow as dashed lines along the anterior surface of the aorta, dotted lines along the posterior segment near the origin of the right pulmonary artery, and two parallel dashed lines on the pulmonary trunk marking the proposed site of flap creation. Illustration B shows the pulmonary artery flap elevated on the right and an aortic flap at the lower center. Surgical forceps hold the edges of both flaps. The pulmonary trunk remains at the upper center, and the aorta sits at the lower portion. Illustration C shows instruments holding the edges of the pulmonary trunk and the right pulmonary artery as a continuous line of stitches forms the right pulmonary artery anastomosis. A curved suture strand trails downward beneath the connection. Illustration D shows the completed repair as the aorta is fully rejoined at the left, the pulmonary trunk rises above the repaired region, and the right pulmonary artery extends to the right. The stitched seam is across the reattached tissues. The signature J RHEAD is written beneath the anastomotic repair.

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Origin of the right or left pulmonary artery from the ascending aorta

Definition

Historical note