This chapter focuses on the management of coronary artery anomalies in patients without other hemodynamically significant heart defects. Although most coronary artery anomalies are of intellectual interest only, there are a few that are clinically significant as they may result in myocardial ischemia, left ventricular dysfunction, and sudden death. The clinically significant anomalies that we will discuss in this chapter are: anomalous origin of a coronary artery from the pulmonary artery, anomalous coronary artery that courses between the aorta and the pulmonary artery, and coronary artery fistulae.

Normally, two coronary arteries arise from separate ostia in the right and left aortic sinuses of Valsalva. The left main coronary artery (LMCA) originates from the left sinus and usually bifurcates into the left anterior descending (LAD) coronary artery and left circumflex coronary artery. The LAD courses in the anterior interventricular groove while the left circumflex coronary artery runs in the left atrioventricular groove. The right coronary artery (RCA) originates anteriorly from the right aortic sinus, runs along the right atrioventricular groove, and usually terminates as the posterior descending artery.

The coronary artery ostia are usually centrally located in the appropriate sinus of Valsalva. However, the ostium may be eccentrically located in some individuals, with the ostium arising close to a valve commissure. The coronary ostia may have a “high takeoff” from the tubular aorta above the sinotubular junction, which is usually benign. It is important to be aware of this anomaly if one needs an aortic valve replacement or requires an aortotomy for another reason, as the coronary artery can be transected if not recognized prior to surgery. When both coronary arteries arise from the same aortic sinus with either a single ostium or two separate ostia (Table 83-1), the anomaly is usually benign if the anomalous vessel courses posterior to the aorta or anterior to the pulmonary artery. However, if either the anomalous LMCA or RCA courses between the two great vessels, this may lead to myocardial ischemia and sudden death.

Anomalous origin of a coronary artery from the pulmonary artery is a rare congenital coronary anomaly that almost always results in early death if not diagnosed and treated promptly.^1,2 Anomalous origin of the LMCA from the pulmonary artery (ALCAPA) is the most common of this class of coronary anomalies and is associated with myocardial ischemia and left ventricular dysfunction. Much less frequently, the RCA may arise from the pulmonary artery in isolation. In extremely rare and usually fatal circumstances, the LAD, the circumflex, or both the LMCA and RCA may arise aberrantly from the pulmonary artery.

ALCAPA is otherwise known as the Bland-White-Garland syndrome after Bland and colleagues reported in 1933 on the clinical and autopsy findings of an infant with this anomaly.³ The incidence of ALCAPA ranges from 1 in 30,000 to 1 in 300,000 individuals. In childhood, this anomaly is the most common cause of myocardial infarction and, if not treated, is associated with a 90 percent mortality rate by age 1 year.

Anatomy

In ALCAPA, the LMCA generally arises from the main pulmonary artery (MPA), although it may arise from the right pulmonary artery. The LMCA most often originates from the rightward aspect of the posterior (facing) sinus of the MPA (Figs. 83-1 and 83-2A–C). Other locations it may originate from are the leftward aspect of the posterior (facing) sinus and, rarely, the anterior (nonfacing) sinus of the MPA (Fig. 83-2C). In the case of an anomalous RCA, the most common location is originating from the anterior portion of the pulmonary artery.

Other associated defects with ALCAPA may include patent ductus arteriosus (PDA), ventricular septal defect (VSD), coarctation of the aorta, and tetralogy of Fallot.

Pathophysiology

During fetal life, the systemic and pulmonary circulation pressures are similar; therefore, in children with ALCAPA, myocardial perfusion remains intact since the pulmonary arterial pressure is systemic. After birth but before ductal closure, the pulmonary artery pressure remains elevated, thus allowing adequate perfusion of the anomalous coronary artery. Because of this, diagnosis of ALCAPA in the first few days of life is rare. Children with ALCAPA will usually develop symptoms after ductal closure and the subsequent fall in the pulmonary vascular resistance. However, the clinical course after ductal closure varies and is largely dependent on the presence or absence of collaterals from the RCA to the left coronary system. If the collateral circulation has not been well established, myocardial ischemia and ventricular dysfunction rapidly occur due to inadequate myocardial perfusion.⁴ Because the pulmonary artery pressure is lower than the systemic pressure, the left ventricle is being perfused with desaturated blood. If there is a PDA or VSD, the pulmonary artery pressure may be elevated, so that the left ventricular perfusion pressure may be adequate and ischemia may not occur. If ALCAPA is not diagnosed prior to closure of these defects, it will become apparent shortly thereafter when the pulmonary arterial pressure drops; the outcome is usually fatal.

If adequate collateralization has been established, then perfusion of the left coronary system is maintained. However, as the pulmonary vascular resistance falls, a shunt develops from the RCA to the pulmonary artery. The RCA and left coronary artery systems progressively dilate with flow reversal in the left coronary leading to a pulmonary-coronary steal. Although the overall shunt is relatively small related to cardiac output, it is significant with regards to coronary blood flow. Children with an extensive collateral system may survive past infancy; however, progressive left ventricular dysfunction will predictably ensue.⁵ In a small number of patients, the collateral vessels are enough to maintain adequate myocardial perfusion at rest and sometimes even during exertion. Because of this, these patients may not be diagnosed until adulthood.⁶ This is rare, however, and most children have severe mitral regurgitation (MR) due to infarction of the posterior leaflet of the mitral valve and subsequent poor movement of the leaflet as well as ventricular dilation; fibrosis and fibroelastosis of the papillary muscle may also be present.

Clinical Presentation

Clinical presentation is usually between 4 and 6 weeks of age when the pulmonary vascular resistance has dropped⁷; however, sometimes infants are not diagnosed until 2 to 3 months of age when symptoms have increased in severity. Presenting signs and symptoms are those of congestive heart failure, including sweating and discomfort with feeding, tachypnea, poor weight gain, and pallor. The apparent discomfort with feeding is thought to represent myocardial ischemia. Those not identified as infants are usually diagnosed at several months of age due to a loud MR murmur. Those not diagnosed during infancy may remain asymptomatic, while others may present with exertional chest pain, presyncope, or syncope. Furthermore, there have been reports of exertional sudden death in older patients. Patients with anomalous origin of the RCA from the pulmonary artery tend to have symptoms to ALCAPA but they may be less severe; however, myocardial ischemia and sudden death can still occur.

On physical examination, an infant with ALCAPA may demonstrate signs of congestive heart failure, including tachypnea, tachycardia, and hepatomegaly. Distinguishing left ventricular dysfunction secondary to ALCAPA from dilated cardiomyopathy can be difficult. Cardiac examination may demonstrate a gallop rhythm and a systolic murmur of MR at the apex. If pulmonary hypertension is present due to left ventricular failure, there may be evidence of right heart enlargement and an accentuated pulmonary component of the second heart sound on examination.

Chest radiography in infants with ALCAPA generally demonstrates an enlarged cardiac silhouette, mainly due to the enlarged left atrium and left ventricle. In those with congestive heart failure, electrocardiogram (ECG) can be a useful diagnostic clue. Classically, there is evidence of lateral or anterolateral wall infarction with Q waves and ST segment elevation in leads I, aVL, and V4-V6. While these electrocardiographic abnormalities can be found in other causes of myocardial infarction or cardiomyopathy, if they are seen in an infant in congestive heart failure, the diagnosis of ALCAPA needs to be strongly considered. Indeed, any infant with dilated cardiomyopathy must be extensively evaluated to rule out ALCAPA. This diagnosis must also be entertained in older children and adolescents with dilated cardiomyopathy since there are patients who survive past infancy.

Diagnostic Imaging

Echocardiography with Doppler color flow usually shows a dilated left ventricle with some degree of MR. An enlarged RCA is almost always noted and should increase suspicion of this diagnosis. Visualization of the origin of both coronary arteries is necessary with the objective of demonstrating the origin of the LMCA from the pulmonary artery. If visualization of the anomalous vessel is difficult, color flow Doppler may be used to show retrograde flow from the LMCA into the pulmonary artery. Nevertheless, if any questions remain about location of both coronary ostia, then cardiac catheterization is mandatory to rule out ALCAPA.

Cardiac catheterization with angiography is the gold standard in diagnosing ALCAPA. In infants with ALCAPA, hemodynamic data may demonstrate elevated filling and pulmonary arterial pressures and a low cardiac output. In older asymptomatic patients, hemodynamic data may show only slightly elevated pulmonary arterial pressures with normal filling pressures and a normal cardiac output. Catheterization data may show a small left-to-right shunt. On aortic root injection, a single, dilated RCA will arise normally from the aorta. If there are significant collaterals, aortic root angiography will demonstrate the collateral blood flow providing late, retrograde filling of the LMCA and a blush of contrast subsequently filling the MPA. Furthermore, if there are significant collaterals with a resultant large left–right shunt, a step-up in oxygen saturation may be noted in the MPA. If the diagnosis remains in doubt, a distal balloon occlusion of the MPA with proximal injection should demonstrate the anomalous LCA.⁸

Magnetic resonance imaging (MRI) has emerged as a useful noninvasive diagnostic tool for delineating congenital coronary anomalies.^9,10 Studies have shown that magnetic resonance angiography has a similar sensitivity and specificity compared to coronary angiography and may be particularly useful in delineating the proximal course of anomalous coronary arteries. Further data are needed before recommending MRI instead of cardiac catheterization. In adults, computed tomography (CT) scan has been used extensively for coronary artery delineation. Although CT scan may be useful in the older patients diagnosed with ALCAPA, exposure to radiation and the need for a slower heart rate with ECG gating generally excludes its use in infants.

Surgical Management

Indications

Surgical repair is necessary in all patients with ALCAPA. Even in infants who present in congestive heart failure, surgery should occur shortly following diagnosis, as the risk of further myocardial ischemia and subsequent death is high.¹¹ In older asymptomatic patients, surgery can be performed electively. If an infant presents in significant heart failure, surgery will likely need to be delayed for at least 24 hours to stabilize the patient using mechanical ventilation, inotropic support, and vasodilators, when necessary. As reported by Del Nido and colleagues, even the sickest infants can withstand surgical repair if left ventricular assist devices (LVAD) are utilized postoperatively.¹² Other critically ill infants may need extracorporeal membrane oxygenation (ECMO). It is important that centers performing ALCAPA surgery have the capability to provide mechanical assistance if necessary; if not, the child should be transferred to a hospital where these services are available.

Restoring a two-coronary system is the surgical goal. Simple ligation of the anomalous coronary should not be performed.¹³ Furthermore, because significant recovery of heart function usually occurs postoperatively, infants presenting with severe left ventricular dysfunction and mitral insufficiency should not be excluded from revascularization. Even if severe MR is present at diagnosis, left ventricular aneurysmectomy and mitral valve repair or replacement are rarely indicated at the time of initial procedure because the severity of MR almost always diminishes after revascularization.

Surgical Techniques

The first successful operation for ALCAPA consisted of ligation of the anomalous vessel at the pulmonary artery, thus preventing the left-to-right shunt. This procedure allowed perfusion of the left ventricle through collaterals from the RCA. However, there was significant operative mortality and risk of late sudden death with this procedure, so a variety of alternative techniques were developed to create a dual coronary artery system. These included coronary artery bypass grafting, creation of an aortopulmonary window, and direct coronary reimplantation.

Coronary artery bypass grafts utilized the left subclavian artery, the internal mammary artery (IMA), and saphenous vein. The first successful left subclavian artery-to-left coronary bypass was first reported in 1968¹⁴; however, the results of bypass grafting, notably with saphenous vein grafts, have been disappointing. The creation of an aortopulmonary window and intrapulmonary artery baffle using a pulmonary artery flap to direct blood flow from the aorta to the anomalous coronary artery was first described by Takeuchi and associates.¹⁵ As experience with the arterial switch operation for transposition of the great vessels has increased, the procedure of choice currently utilized in most institutions is direct reimplantation of the anomalous coronary into the aorta.^16,17

Coronary Artery Bypass Grafting.

Coronary artery bypass grafting is rarely utilized in patients with ALCAPA. If necessary, it is typically used as a way to create a dual coronary artery system after previous ligation or due to stenosis or occlusion after a previous attempt at repair. In these cases, the IMA is the conduit of choice and can be successfully used even in neonates and infants. There is some evidence for growth of the IMA after bypass grafting^18–20 in pediatric patients. Grafts using the saphenous vein are not recommended due to the risk of occlusion and poor long-term results,²¹ and should only be utilized if no other option is available. Similarly, left subclavian-to-left coronary artery anastomosis is not frequently utilized due to the risk of stenosis or occlusion.^22,23

Direct Reimplantation.

Direct reimplantation of the anomalous coronary artery onto the aorta can be performed in most patients with ALCAPA (Figs. 83-3–83-6).^24,25 The procedure is fairly straightforward when the anomalous coronary ostium is in the posterior-facing sinus. Even if the ostium is located in the non-facing sinus, direct implantation is possible by excising a large button of pulmonary artery to extend the coronary artery.

A median sternotomy is performed after induction of anesthesia and placement of monitoring lines. The thymus is resected. The pericardium is opened and suspended in stay sutures. Contact with the myocardium should be kept at a minimum until the patient is placed on cardiopulmonary bypass due to the risk of ventricular fibrillation from myocardial ischemia and left ventricular dysfunction. This operation may be performed using either continuous low-flow bypass with moderate hypothermia (25–28°C) or deep hypothermic circulatory arrest (18°C) in very small infants. An aortic purse-string suture is placed distally near the innominate artery and another is placed in the right atrial appendage for a single venous cannula prior to cannulation. Heparin is administered, the aortic and right atrial cannulae are inserted, and cardiopulmonary bypass is established. Decompression of the left ventricle should be performed by placing a left ventricular vent via the right superior pulmonary vein. Although on bypass, the pulmonary artery and epicardial course of the left coronary artery are visualized. Direct reimplantation may not be possible if the anomalous left coronary originates far leftward in the posterior-facing sinus or on the anterior non-facing sinus.

The aorta and both pulmonary arteries are fully mobilized. The ductus (or ligamentum) arteriosus is ligated to improve mobility of the pulmonary artery. Tourniquets are placed around both the right and left branch pulmonary arteries to occlude the branch pulmonary arteries and prevent run-off of cardioplegia solution into the lungs. Another way to prevent run-off is to compress the coronary artery origin from the pulmonary artery during administration of cardioplegia solution. A cannula is inserted in the ascending aorta for administration of cardioplegia solution, the aorta is cross-clamped, and cold cardioplegia is administered via the aortic root. If circulatory arrest is utilized, the head vessels are then occluded with tourniquets, the circulation is arrested, venous blood is drained into the reservoir, and the cannulae are removed.

After adequate arrest, the pulmonary artery is opened transversely just above the sinotubular junction (Fig. 83-3) and the anomalous coronary orifice is noted. Similar to the procedure used for the arterial switch operation, the pulmonary artery is divided and the coronary ostium is excised from the posterior aspect of the pulmonary artery using a generous button of arterial wall. The excised segment of the pulmonary wall extends the proximal end of the coronary artery, thereby allowing for the aortic anastomosis to be accomplished without tension. The pulmonary commissure may need to be taken down if the coronary ostium is located near a commissure. Alternatively, if the coronary arises anteriorly from the pulmonary artery or from a branch pulmonary artery and above the commissures, one can extend the coronary artery by using a tube constructed from pulmonary artery wall to allow reimplantation (Fig. 83-4). The proximal portion of the coronary artery is mobilized using cautery, exercising caution to avoid any small branches. Just as in the arterial switch operation, the aorta is then opened transversely directly above the sinotubular junction and the incision is carried posteriorly over the left posterior-facing sinus (Fig. 83-5). The sinus is then incised vertically to accept the coronary button. The coronary button is carefully aligned with the aortic incision to avoid twisting or kinking. Using a continuous suture of 7-0 polypropylene (Prolene), the anastomosis is begun at the most inferior aspect of the coronary button, which is attached to the most inferior aspect of the incision in the sinus. The suture line is carried to the top of the incision anteriorly and posteriorly. The aorta is closed using a continuous suture of 7-0 Prolene, which is tied to the coronary button suture as the anastomosis is completed (Fig. 83-5). After aortic closure, cardioplegia solution is administered and the anastomotic site is inspected for adequate filling of the coronary as well as for hemostasis.

In most cases, the pulmonary artery can be repaired using a continuous suture of 7-0 Prolene. Division of the ductus will improve mobility of the pulmonary artery confluence and allow reconstruction without tension. If there is tension or narrowing, or if the defect left by excision of the coronary artery button is sizeable, the pulmonary artery should be repaired with a patch of autologous pericardium (Fig. 83-6). If a commissure was taken down during excision of the coronary button, the pulmonary artery should be reconstructed with pericardium and the commissure resuspended.

The patient is then rewarmed and the aortic cross-clamp is removed. Alternatively, the cross-clamp may be removed before the pulmonary artery reconstruction to minimize ischemic time. The left ventricle is inspected to assess for adequacy of perfusion, and suture lines are inspected for hemostasis. Right and left atrial lines are placed to adequately monitor pressure and for drug administration. Atrial and ventricular pacing wires are also placed. The patient is separated from cardiopulmonary bypass after complete rewarming.

The ECG should be monitored closely for evidence of ischemia during reperfusion and after separation from bypass. Inotropic support may be temporarily necessary due to preoperative left ventricular dysfunction.

Modified Takeuchi Operation.

The Takeuchi operation, or intrapulmonary artery tunnel, is an alternative surgical strategy for repair of ALCAPA. Takeuchi and colleagues first described the creation of an aortopulmonary window using a portion of the anterior pulmonary artery wall to create a baffle which would direct blood from the aorta to the anomalously located left coronary artery ostium.¹⁵ In the modified repair, a polytetrafluoroethylene (PTFE, Gore-Tex) patch is used to construct the baffle. However, creating a baffle may not be possible if the ostium is located near a commissure or arises from a branch pulmonary artery.

The procedure may be performed with either continuous low-flow cardiopulmonary bypass (25–28°C) or deep hypothermic circulatory arrest (18°C). Cannulation is performed as described above for direct reimplantation. After induction of cardioplegic arrest, a longitudinal incision is made in the anterior portion of the pulmonary artery (Fig. 83-7) and the ostium of the anomalous coronary is identified. Using a punch, a 5-mm diameter opening is made on the leftward aspect of the aorta above the sinotubular junction (Fig. 83-8). If there is any question regarding placement of the aortic opening, an anterior aortotomy should be performed and the incision visualized directly to avoid damage to the aortic valve. By creating the aortopulmonary window above the sinotubular junction, this allows a downward angle of the baffle into the sinus if the ostium is located deep within a sinus. After a similar incision is made in the pulmonary artery directly opposite to the aortic opening, these are anastomosed using a continuous suture of 7-0 Prolene creating an aortopulmonary window (Fig. 83-8). A 4-mm PTFE tube graft is split longitudinally and customized to an appropriate length (Fig. 83-9). This graft functions as an intrapulmonary artery tunnel, baffling blood from the aortopulmonary window to the anomalous coronary ostium. The suture line starts at the anomalous coronary and is continued inferiorly along the pulmonary artery wall to the aortopulmonary window. The suture line then returns to the coronary artery to complete the superior aspect of the baffle. After the baffle is created, repair of the pulmonary artery is performed using a prosthetic patch or autologous pericardium to avoid supravalvar pulmonary artery obstruction (Fig. 83-10). The most common complications of the modified Takeuchi operation include baffle leak, baffle occlusion, and supravalvar pulmonary artery obstruction.

Postoperative Management

Regardless of which surgical technique was utilized, the most common postoperative issues are those related to the infant’s preoperative state: low cardiac output, left ventricular dysfunction, and hypotension. Optimizing the patient’s hemoglobin, electrolytes, acid-base and fluid status, and providing adequate inotropic support are extremely important. LVAD or ECMO support may be temporarily necessary in infants and children with severe preoperative cardiac dysfunction. Bleeding is also a common postoperative issue and is more frequently encountered in small infants and those who require mechanical support. Platelets and fresh frozen plasma should be used aggressively to replace ongoing losses. Patients with low cardiac output and/or bleeding issues may be candidates for delayed sternal closure.