Pathophysiology

The first pathophysiologic explanation of coronary flow patterns in patients with ALCAPA was described by Edwards [10]. The onset of symptoms and the degree of myocardial ischemia depend on a balance between the rapidity of patent arterial duct closure, maintenance of pulmonary hypertension, and development of intercoronary collateral vessels to provide retrograde perfusion from the right coronary artery (RCA) to the ALCAPA. In fact, surgical ligation of a patent arterial duct in small infants has led to intraoperative ventricular fibrillation and cardiac arrest, unmasking ALCAPA by dropping the pressure in the pulmonary artery [8, 11]. Historically, ALCAPA patients have been divided into two groups, “infantile” and “adult,” according to their coronary circulation patterns [10]. The infantile type has little or no intercoronary collateral development, resulting in early onset of symptoms within days to weeks after birth. Severe myocardial ischemia, left ventricular dysfunction and dilatation, mitral regurgitation from papillary muscle ischemia, and rapid death can occur. Adult‐type circulation accounts for 10–15% of cases with Bland–White–Garland syndrome and depends on intercoronary collateral vessels from the RCA that provide adequate flow into the anomalous left coronary artery. These patients may have no symptoms for decades and only mild to moderate degrees of myocardial ischemia. Survival to adulthood depends on a large dominant RCA and/or a restrictive opening between the anomalous left coronary artery and the pulmonary artery. Sudden death occurs in 80–90% of patients at a mean age of 35 years [12], indicating the severity of the process even in asymptomatic patients, thereby justifying surgical therapy upon diagnosis.

Clinical Features

In infants and toddlers, clinical findings of ALCAPA range from unspecific feeding problems, irritability, and grunting, to sweating, dyspnea, atypical angina, and sudden death [13]. Pediatric emergency room presentations range from failure to thrive to diagnoses of asthma or recurrent wheezing, and should raise the suspicion of ALCAPA [13]. Most patients have moderate to severe congestive heart failure with cardiomegaly on chest radiograph, ischemic signs on electrocardiogram, and a murmur of mitral insufficiency on auscultation. Left‐axis deviation on the electrocardiogram points to significant RCA‐dominant circulation [14]. Two‐dimensional echocardiography can be diagnostic (Figures 39.2 and 39.3) [15]. Images show the enlarged, dilated RCA, and a grossly hypokinetic and dilated left ventricle. A left‐to‐right shunt may be demonstrated by pulsed and color flow Doppler ultrasonography from reversal of flow from the anomalous left coronary artery into the pulmonary artery. When necessary, MRI, CT angiography, or cardiac catheterization is used to exclude another coronary anomaly responsible for myocardial ischemia [16, 17], to define coexisting intracardiac defects, or to exclude the ALCAPA before settling for the diagnosis of idiopathic dilated cardiomyopathy [7]. It is extremely important that the diagnosis of ALCAPA be excluded prior to committing to a diagnosis of dilated cardiomyopathy. The typically enlarged RCA, the characteristic blush from the anomalous left coronary artery into the pulmonary artery, as well as associated mitral valve regurgitation are salient features (Figure 39.4) [15]. Myocardial viability studies such as dobutamine echocardiography, thallium CT myocardial perfusion imaging, or positron emission tomography (PET) scans may be used to assess hibernating myocardium. However, they are only relevant to influencing surgical strategy in patients with massive infarction or aneurysmal tissue, whereby coronary revascularization techniques would not be expected to improve myocardial function [7]. Documented absence of viable tissue would be the only indication to consider heart transplantation over myocardial reperfusion [18].

Surgical Management

Medical therapy plays no role in the treatment of this anomaly other than stabilizing the patient prior to surgical intervention. Willis Potts is the first surgeon credited with surgical repair, creating an aortopulmonary anastomosis to increase pulmonary artery blood flow and oxygen saturation in the anomalous coronary artery [19]. In 1953, Mustard performed a left common carotid to ALCAPA end‐to‐end anastomosis [20]. In 1959, Sabiston ligated the ALCAPA at its origin to prevent the left‐to‐right steal in the coronary artery [21]. Cooley and associates performed the first saphenous vein graft to the ALCAPA in 1960 [22], followed by Meyer and associates using the left subclavian artery as a bypass graft [23]. Left internal thoracic arterial bypass grafting for left main coronary atresia was described by Fortune and associates in 1987 [24]. Neches and colleagues were the first to describe direct reimplantation of the anomalous left coronary into the aorta in 1974, transferring it with a button of pulmonary artery [25]. This remains the current preferred option toward achieving a definitive two coronary artery anatomy and physiology (Figures 39.5 and 39.6) [16]. In 1979, Takeuchi and coworkers devised an operation for cases in which direct implantation is not feasible [26], owing to unfavorable coronary artery anatomy or lack of length for a coronary button (Figures 39.7 and 39.8) [15]. In the procedure bearing his name, an intrapulmonary baffle is used to reroute the ALCAPA to the ascending aorta (Figure 39.9). Arciniegas described interposing a segment of free subclavian artery to compensate for lack of length [27]. In the presence of a nonfacing sinus origin of the ALCAPA or other challenging anatomic variations, extending a cuff of pulmonary trunk tissue to elongate the coronary artery [28] or other creative surgical techniques gained through the experience from coronary transfer for arterial switch operations will allow aortic reimplantation [14, 16–18].

In 1988, Mavroudis and colleagues performed cardiac transplantation as a last‐resort solution for patients with end‐stage left ventricular failure from myocardial infarction [29], as documented by viability studies.

In adults, direct reimplantation of the ALCAPA may be technically more difficult because of increased coronary artery friability, diminished elasticity for mobilization, the potential for tearing, or stenosis resulting from anastomotic tension [7, 30, 31]. In adults with ALCAPA, coronary artery bypass grafting using the internal thoracic artery with proximal ligation at the ALCAPA ostium is preferred by some [32, 33]. Others employ a polytetrafluoroethylene (PTFE) interposition graft to connect the ascending aorta with the proximal main coronary button (Figure 39.10) [34]. Importantly in adult patients, anticoagulation with coumadin should be prescribed, as there is a significant risk of thrombosis of the decompressed RCA.

Adequate myocardial protection with optimal administration of cardioplegia is a crucial point common to all surgical techniques. Backer and associates described a cardioplegia strategy for aortic reimplantation that allows maximal myocardial protection, regardless of the degree of RCA collateralization [16]. After ligation of the arterial duct and snaring the pulmonary arteries, an initial dose of antegrade blood cardioplegia is administered into the ascending aorta. The pulmonary artery is carefully transected and mobilized for maximum visibility, and the ALCAPA button is excised. A second dose of antegrade cardioplegia is then given while the orifice of the ALCAPA is occluded, after which the coronary transfer is performed into the aorta. Aortic cross‐clamp is then removed and the pulmonary artery reconstruction performed with a beating, fully perfused heart. The authors reported no operative mortality, and no postoperative need for a left ventricular assist device or extracorporeal membrane oxygenation (ECMO) in 16 consecutive patients [16].

Surgical correction of ALCAPA addresses the global left ventricular function and the ischemic mitral valve insufficiency. Ischemic yet viable myocardium, as assessed with stress thallium‐201 or dipyridamole stress echocardiography, will recover postoperatively after reperfusion by any procedure that results in a two coronary artery system [7, 12, 17, 18, 28, 35–43]. Infarcted myocardium or ventricular aneurysm will not recover. However, in most cases, the delineation between infarcted and hibernating myocardium is not clear. Accordingly, resection of left ventricular muscle is hardly ever justified [7, 18, 44]. Some controversy still surrounds surgical intervention on the mitral valve. Mitral regurgitation is related to both ischemic left ventricular dilatation and ischemic dysfunction of the papillary muscles [7, 43]. Even severe mitral insufficiency often regresses after coronary reperfusion [7, 16, 18, 27, 28, 36–38, 45]. Although some authors advocate mitral valve annuloplasty or mitral valve replacement in cases of severe mitral regurgitation [12, 35, 46, 47], most agree that mitral regurgitation need not be addressed during initial surgery for reimplantation of ALCAPA [7, 16, 18, 27, 28, 36–38, 45]. After improvement of left ventricular function, persistent significant mitral insufficiency can be repaired at a later operation. After initial ALCAPA reimplantation, Huddleston and coworkers stressed the importance of following mitral valve function as an indirect sign of coronary patency [45]. Indeed, persisting, recurring, or worsening mitral valve insufficiency and left ventricular function may be a sign of coronary stenosis, warranting cardiac catheterization to document coronary patency, prior to reoperation for a mitral valve procedure [7, 45, 48].

Results

The combined operative mortality of all commonly used surgical techniques ranges from 0% to 23% [7, 12, 14, 16–18, 27, 28, 30–36, 38, 45–47]. Late death is unusual. Reperfusion through a two coronary artery system with documented long‐term patency should eliminate the risk of sudden death [47, 49]. Potential surgical complications include acute intraoperative coronary insufficiency resulting from technical error, bleeding, and aneurysm of the reimplanted left coronary artery button [49]. Complications specific to the Takeuchi procedure include supravalvar pulmonary stenosis (76%), baffle leaks leading to coronary–pulmonary artery fistula (52%), and aortic insufficiency [36]. Reoperations or catheter interventions for the Takeuchi procedure are frequently necessary to correct these complications and are reported to be as high as 30% [36, 48, 49]. Reoperations include mitral valve repair/replacement, and pulmonary artery plasty for supravalvar pulmonary stenosis [49].

After successful reimplantation of ALCAPA, poor preoperative left ventricular function, stunned myocardium, or intractable ventricular arrhythmias may prohibit weaning from cardiopulmonary bypass [7, 49]. Encouraging results have been achieved with the use of mechanical support as a bridge to recovery. Possibilities include ECMO and left ventricular assist devices [30, 45, 49–54]. Although optimization of intraoperative cardioplegia strategies – using both antegrade and retrograde cardioplegia – combined with appropriate postoperative inotropic support should obviate the need for mechanical circulatory support [16], assist devices and ECMO are sometimes necessary and play an integral part in the modern surgical treatment of patients with ALCAPA [7, 49].

Operative risk factors for mortality include decreased preoperative left ventricular function [14, 18, 35] and delay in diagnosis [55, 56]. Although younger patients may present with severe left ventricular failure, early surgery usually results in rapid and eventual complete recovery of myocardial function. Severe mitral regurgitation was found in one series to be a risk factor for poor outcome after surgery [36].

Discussion

Medical treatment has essentially no role in the management of ALCAPA. Surgery is indicated upon diagnosis. The surgical goal is to achieve reperfusion through a two coronary system, most commonly by reimplantation of the ALCAPA into the aorta, which is feasible in almost all instances despite anatomic variability [7, 16, 18, 27, 30–32, 45–47]. In developing countries with limited resources or access to bypass machines, an off‐pump left subclavian artery to left anterior descending anastomosis combined with ostial ALCAPA ligation may be a reasonable alternative to coronary translocation, with six‐year follow‐up including normal exercise tolerance and documented normal ventricular function by echocardiography [55].

Regardless of degree of preoperative left ventricular impairment, an early surgical approach is warranted, as it is the only possible way to salvage hibernating but viable myocardium [7, 16, 18, 47, 51]. Mild to moderate mitral insufficiency regresses after reperfusion and does not have to be addressed at the first operation [7, 14, 18, 30, 36, 38, 44, 47]. Accordingly, preoperative mitral regurgitation has not been shown to increase operative mortality [7, 14, 18, 35, 38, 44], except in one report [36]. Some authors advocate intervening on the mitral valve systematically [46] or if ischemic lesions of the papillary muscles are present [56]. Persistent, recurring, or worsening postoperative mitral insufficiency should warrant a cardiac catheterization to demonstrate coronary patency prior to reoperation on the mitral valve [43, 48]. Left ventricular function improves substantially after restoring a two coronary artery circulation, although some degree of chronic impairment from preoperative structural abnormalities may persist. Left ventricular muscle or aneurysm resection is generally unnecessary [18, 43]. Documented massive infarction may be the only justification for cardiac transplantation, although this situation is fortunately becoming rare, with a higher awareness of the probable diagnosis of ALCAPA even in the neonatal period, an increased index of suspicion, and immediate referral. Left ventricular assist devices and ECMO improve survival in the surgical management of ALCAPA [35, 45–47, 50–52].

The best follow‐up method for patients with ALCAPA is probably with serial ECGs and echocardiogram. Holter monitoring, stress thallium scanning, and cardiac catheterization have shown equivocal results. MRI may demonstrate subtle myocardial damage, and is a good, noninvasive, radiation‐free investigation for the postsurgical evaluation of ALCAPA [57].

Left Main Coronary Artery from Right Aortic Sinus of Valsalva

LMCA arising from the RASV represents the most serious anomaly of coronary origin and is associated with the highest incidence of symptoms and sudden death [3, 60–73, 78, 80]. The incidence of sudden death in untreated patients reaches 57%, and up to 66% are related to exercise [60, 72, 77]. The risk of sudden death is reported as high as 82% if the LMCA courses between the great vessels [60, 77, 78]. Four courses of “left from the right” AAOCA are possible in relation to the great vessels: (i) anterior to the pulmonary artery; (ii) posterior to the aorta; (iii) between the great vessels; and (iv) septal course through the conal septum (beneath the right ventricular infundibulum) [77]. If the LMCA courses between the great vessels, it provides one or two branches to the proximal ventricular septum. Conversely, when the aberrant LMCA is posterior to the aorta, there are no septal branches from the left coronary system, rising rather from the RCA [75]. The most important patho‐anatomic element of an anomalous LMCA is an intramural course that is almost always stenotic, both at its orifice and over the intramural course. The intramural course can be above the commissure, between the left and right coronary cusps, or below the commissure.

The presumed pathogenesis of ischemia and sudden death includes an acute origin (angle) of the anomalous vessel causing a slit‐like orifice [60, 61, 72, 75, 77, 78, 80], compression of the coronary artery by aortic root distension at the onset of diastole [60, 77], exercise‐induced expansion of both the aortic root and the pulmonary trunk causing compression of the LMCA [59], effort‐related stretching of the intramural LMCA segment adherent to the aorta along its first 1.5 cm of length [72, 77], and compression of the LMCA by the intercoronary commissure, particularly during diastole when the aortic valve is closed [72], with resultant spasm, torsion, or kinking [60, 75]. The incidence of atherosclerosis is higher among older patients with aberrant LMCA than among age‐matched controls. The left system can be congenitally small, and many of these patients have a right‐dominant circulation [70, 75].

Symptoms are frequent, encountered in as many as 54% of patients [60, 65, 70, 81]. These include angina, angina during exercise, congestive heart failure, syncope, palpitations, gastrointestinal symptoms [81], and myocardial infarction. Their presence may be indicative of the increased risk of sudden death. Angina and syncope predominate among younger patients, while those older than 30 years experience angina and myocardial infarction [61]. Younger patients are more prone to sudden death, which may be their presenting symptom [60, 61]. In a postmortem study of 6.3 million US military recruits (ages 17–35 years) undergoing basic military training between 1977 and 2001, 64 sudden cardiac deaths were identified [65]. Of these, the majority (61%) were related to coronary artery pathology, of which more than half (54%) were anomalous aortic coronary origins. Sudden cardiac deaths were more likely associated with premortem exertional chest discomfort and/or syncope, compared to deaths resulting from other coronary artery disease in the same cohort.

Right Coronary Artery from Left Aortic Sinus of Valsalva

Anomalous RCA arising from the LASV is reported in 0.26–0.6% of postmortem studies and 0.2% of all angiographic studies and is one of the most common of all coronary anomalies [80, 82]. Anomalous RCA from LASV was previously considered benign, but more recently is recognized for being associated with considerable potential morbidity [34, 60, 73, 82] and potential risk for sudden death, often related to exercise [60, 62–68, 71–73]. Symptoms of angina, myocardial infarction, syncope, and high‐grade atrioventricular block [60, 73, 80–84] are believed to be related to closure of the anomalous ostium within the aortic wall during exercise or hypertensive states [63–68, 82]. Proposed mechanisms of coronary ischemia and resultant left ventricular dysfunction during exertion include enlargement of the aortic root and pulmonary artery, which in turn can obstruct coronary flow during diastole [73, 82]. As in the case of “left from the right” AAOCA, a “right from the left” AAOCA has the same potential for intramural courses and stenotic patterns. The anatomic configuration can be above the commissure, between the right and left coronary cusps, or below the commissure.

Anomalous Circumflex Coronary Artery from Right Aortic Sinus of Valsalva or Right Coronary Artery

The reported incidence of this anomaly is 0.2–0.71% [76], which represents the most common coronary variation (60%) as reported in the Coronary Artery Surgery Study [74]. The anomalous circumflex coronary artery originates most often from a separate ostium in the RASV (69%), and in 31% as a direct branch of the RCA. Symptoms and sudden death are rare in these patients. The incidence of atherosclerotic coronary artery disease is similar to that in the control population [76].

Surgical Management

Expert consensus guidelines from the American Association for Thoracic Surgery include the following recommendations for surgical intervention [85]:

• Patients with AAOCA and symptoms, syncope, or aborted sudden cardiac death should be offered surgery (class I).
  
• Asymptomatic patients with anomalous aortic origin of the left coronary artery (AAOLCA) and an interarterial course should be offered surgery (class I).
  
• Asymptomatic patients with anomalous aortic origin of the right coronary artery (AAORCA) should be evaluated for inducible ischemia, and if asymptomatic and without ischemia, they may be observed and allowed to resume competitive athletics (class IIa).

Symptomatic patients require surgical intervention upon diagnosis; a coronary imaging study is performed, and surgery is planned. Patients with an anomalous left coronary artery present more often with symptoms than patients with an anomalous RCA [63]. However, with anomalous “left from the right” AAOCA, surgery is indicated even in the absence of symptoms [80], and patients are recommended to undergo prophylactic corrective surgery to avoid a high risk of sudden death [60, 63, 66, 68, 71, 72, 80]. The surgical indication becomes emergent if the patient has exertional syncope, chest pain, or ventricular tachycardia [70, 78]. In the asymptomatic patient with LMCA from RASV, some authors recommend delaying surgery until 10 years of age, based on the fact that sudden death is rare in children [68]. This view is not universal [72]. If surgical repair is refused, strenuous physical activity and competitive athletics should be avoided [66, 69]. In the asymptomatic young patient with an aberrant “right from the left” AAOCA, treatment is controversial [63]. In the subgroup of asymptomatic older patients with nonconclusive results of a thallium study or absence of atherosclerotic coronary lesions, no sudden death is described [61, 63, 70]. Until recently, most centers have not performed prophylactic surgery on this cohort of asymptomatic patients, although this trend appears to be changing with a less conservative approach favoring surgery in selected patients with the anomalous coronary coursing between the great vessels [68]. Current analysis is being performed by the Congenital Heart Surgeons’ Society (CHSS) in a multi‐institutional study to better define the indications [81, 85, 86].

The aim of surgery is to restore a normal anatomic position of the left or right anomalous coronary ostium [72], or to bypass a problematic proximal juxtacommisural or intramural course that may or may not have atherosclerotic lesions. The first attempts at surgical correction were performed using saphenous vein grafts to bypass the aberrant coronary arteries, followed shortly by internal thoracic artery bypass grafting. Although these techniques are still practiced [63, 67, 68, 71] and remain unavoidable in certain circumstances, they expose the patient to the usual problems of grafted coronary artery disease and potential reintervention [68]. Furthermore, as the flow through the anomalous coronary is most often normal at rest, any type of bypass graft may have decreased postoperative patency owing to competitive flow [66, 68], raising the question of whether the proximal aberrant coronary should be ligated [67]. We do not recommend this approach.

In 1982, Mustafa and Yacoub were the first to perform an anatomic ostial correction consisting of opening the aortic root, incising the ostium of the LMCA, and unroofing the stenotic intramural segment along its course to the midpoint of the LMCA sinus, with detachment of the intercoronary commissure [72]

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