This chapter discusses the range of congenital coronary anomalies that may be found in an otherwise structurally normal heart, first reviewing the anatomy and development of the coronary arteries before focusing on the most clinically significant anomalies of coronary artery origin and course.
Anatomy and Development
Even in the normally structured heart, the coronary arteries can have multiple anomalous origins and epicardial courses. However, such lesions involving the coronary arteries are also frequent when the heart is congenitally malformed. Patterns of origin from the aortic valvar sinuses other than normal are particularly common in lesions such as transposition or the Taussig-Bing variant of double-outlet right ventricle. An abnormal epicardial course is a significant finding in the setting of tetralogy of Fallot. These aspects are addressed in the relevant chapters in this book pertaining to these lesions. This chapter is concerned with abnormal patterns found in individuals having concordant atrioventricular and ventriculoarterial connections and with intact septal structures. The coronary arterial malformation can be the major lesion in this setting, such as when one, or rarely both, of the coronary arteries arises from the pulmonary trunk rather than the aorta. However, not all the variations are overtly of clinical significance. Even some of the arrangements known to cause sudden death can remain asymptomatic until underscoring the catastrophic event. It is a truism, nonetheless, that diagnosis is enhanced by knowledge of the possible arrangements and their potential significance. At present, there is no consensus as how best to classify the multiple variations. The old approach, in which lesions were considered to be major or minor, has foundered simply because many of the allegedly major variations fail to produce symptoms during life. A simple categorization, from the anatomic stance, recognizes first the anomalous sinusal origin of an artery, with subsequent attention being paid to any anomalous epicardial course, not forgetting other abnormal situations, such as myocardial bridging, abnormal communications, duplication of arteries, and a solitary coronary artery ( Box 46.1 ).
Ectopic Origin of Coronary Artery
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From pulmonary trunk
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From right pulmonary artery
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From left pulmonary artery
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From brachiocephalic artery
Anomalous Aortic Sinusal Origin
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Right coronary artery arising from sinus 2
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Main stem of left coronary artery arising from sinus 1
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Circumflex artery arising from sinus 1
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Anterior interventricular artery arising from sinus 1
Anomalous Epicardial Course
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Retro-aortic
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Interarterial
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Prepulmonary
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Intramural
Solitary Coronary Artery
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Solitary coronary artery from sinus 1
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Solitary coronary artery from sinus 2
Abnormal Fistulous Connections
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Connections with a cardiac cavity
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Coronary arteriovenous fistulas
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Coronary to extracardiac arterial or venous connections
Duplication of Coronary Arteries
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Duplication of major epicardial coronary artery
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Woven coronary artery
Clinically, particular congenital abnormalities of the coronary arteries can result in sudden cardiac death, a dilated, poorly functioning ventricle due to myocardial infarction, or chronic ischemia due to a myocardium that is dependent on collateral vessels. Those lesions most at risk include an anomalous origin of the left main coronary artery from the pulmonary artery trunk, some variations of anomalous aortic origin of the coronary artery from the aorta ( Table 46.1 ), and coronary ostial atresia. These risks are discussed later with the clinical information on each lesion.
| Anomaly | Association With Sudden Cardiac Death? |
|---|---|
| Anomalous aortic origin of the right coronary artery from the left sinus with an intramural course | Yes, but rare; greatest risk in young athletes |
| Anomalous aortic origin of the left main coronary artery from the right sinus with an intramural course | Yes; greatest risk in young athletes |
| Anomalous aortic origin of the left main coronary artery from the right sinus with intraseptal/intraconal course | None reported |
Ectopic Origin of the Coronary Arteries
Coronary arteries can rarely arise from a brachiocephalic artery ( Fig. 46.1 ). However, the most significant ectopic origin is when one or more of the coronary arteries arises from the pulmonary trunk, or from the right or left pulmonary artery. Either the left coronary artery or right coronary artery (RCA) can arise from the pulmonary trunk, or very rarely both coronary arteries. Anomalous origin of the left coronary artery is most frequent ( Fig. 46.2 ), producing Bland-White-Garland syndrome.
Early diagnosis permits rapid surgical correction. In most instances, the artery arises from the sinus of the pulmonary trunk adjacent to the left coronary aortic sinus ( Fig. 46.3 ). Less frequently, the artery can arise from a branch of the pulmonary trunk, including the right pulmonary artery. It takes a much longer course to reach the heart ( Fig. 46.4 ). Clinical evolution depends on the extent of development of a collateral circulation. The artery arising from the pulmonary circuit is usually small and thin walled. The RCA, which retains aortic origin, undergoes compensatory enlargement. If the collateral circulation is well developed and distributed, the left ventricle can remain well perfused, with the heart retaining its form and function. More frequently, the collateral circulation is poorly developed. The left ventricle becomes ischemic, dilated, infarcted, and fibrosed ( Fig. 46.5 ). This appearance can mimic dilated cardiomyopathy, particularly if the fibrosis involves the papillary muscles, producing mitral valvar incompetence. Hence anomalous pulmonary origin of a coronary artery must always be excluded when considering the diagnosis of dilated cardiomyopathy in childhood. If the RCA is taking ectopic origin, it usually arises from the pulmonary valvar sinus adjacent to the right coronary aortic sinus. Origin of both coronary arteries from the pulmonary trunk is very rare but can be diagnosed in life and treated surgically.
Anomalous Aortic Origin of the Coronary Arteries
Abnormal aortic origin can take several forms. For example, high take-off relative to the sinutubular junction, when excessive, is anatomically anomalous, although origins minimally above the sinutubular junction are common. It is abnormal sinusal origin that is now recognized as being of far more significance ( Fig. 46.6 , left panel ), particularly if associated with a so-called intramural course (see Fig. 46.6 , right panel ). Recognition of abnormal sinusal origin means that it is necessary uniformly to distinguish between the sinuses themselves, irrespective of the relationship between the arterial trunks. This can be done by assessing the view of the sinuses obtained by the observer, figuratively speaking, standing in the nonadjacent aortic sinus ( Fig. 46.7 ). When taking an anomalous origin, the abnormal vessel will almost always continue to arise from one or another of the two sinuses adjacent to the pulmonary trunk. Using the convention suggested previously, which is equally valid in hearts with abnormal ventriculoarterial connections, the sinuses adjacent to the pulmonary trunk will either be to the right side or left side of the observer. Convention now dictates that the right-side sinus is considered sinus 1, with the left-side sinus deemed to be sinus 2. This approach also accounts for anomalous origin of a major coronary artery from the nonadjacent sinus. Although this sinus is usually described as being noncoronary, that term is obviously inappropriate when the sinus gives rise to a coronary artery. Such origin, in the absence of associated lesions, is unlikely to be of clinical significance unless associated with the intramural pattern.
Coronary arteries arising ectopically from the aorta can also take an anomalous course relative to the arterial roots. Such anomalous courses can be retroaortic, interarterial, or prepulmonary. When the anomalously arising artery runs between the arterial trunks, the arrangement is often described as being “interarterial.” The course can, indeed, extend deep within the crest of the muscular ventricular septum, but more usually the artery runs at the level of the sinutubular junction or within the area of fibro-adipose tissue separating the aortic root from the free-standing subpulmonary infundibular sleeve. It is again the initial course of the artery that is more important. It is more likely to be constricted when running within the wall of the aorta, particularly when crossing the peripheral attachments of the leaflets at the sinutubular junction, the so-called intramural arrangement (see Fig. 46.6 , right panel ). Although any possible anomalous course must be anticipated, there are well-recognized common patterns. Anomalous origin of the left coronary artery or the circumflex artery from sinus 1, for example, or from the RCA, is often associated with a retroaortic course through the transverse pericardial sinus ( Fig. 46.8 ).
Unless also associated with an intramural origin, such course through the transverse sinus or a prepulmonary course is unlikely to produce compression. It is the arrangements associated with an intramural origin therefore that are of greatest significance. They can also be found when the main stem of the left coronary artery takes its origin from sinus 1 ( Fig. 46.9 ). However, more usually, the intramural arrangement is associated with origin of the RCA from sinus 2. Solitary arteries can also have an intramural origin (see later).
Duplication of Coronary Arteries
The anterior interventricular artery is most frequently duplicated, although any of the three major coronary arteries can be involved. So-called woven coronary arteries are a rare variant of duplication. Duplication is usually benign, occurring in up to 1% of the general population.
Solitary Coronary Artery
Solitary origin of the three major coronary arteries can in itself be a substrate for sudden cardiac death. There are at least three patterns. In one variant, the solitary artery, which can arise either from sinus 1 or sinus 2, branches to give rise to the RCA, circumflex, and anterior interventricular (left anterior descending) arteries. If arising from sinus 2, the RCA usually takes a prepulmonary course ( Fig. 46.10 ). If arising from sinus 1, such a branching solitary coronary artery usually gives rise to a main stem of the left coronary artery, which passes between the arterial trunks before branching again to supply the circumflex and anterior interventricular arteries. However, a solitary artery can take a subtly different course. If it emerges from sinus 2, it divides initially into its anterior interventricular and circumflex branches, but the circumflex branch continues beyond the crux to enter the right atrioventricular groove, supplying the myocardium usually fed by the RCA ( Fig. 46.11 , left panel ). When arising from the right coronary aortic sinus, or sinus 1, the solitary artery itself continues beyond the crux, running through the left atrioventricular groove to terminate as the anterior interventricular artery. An associated transmural course will carry the increased risk of sudden cardiac death. Sudden cardiac death has also been associated with atresia of the main stem of the left coronary artery, with the RCA effectively functioning as a solitary artery ( Fig. 46.12 ).
Fistulous Connections
Fistulous communications between the ventricular cavities and the epicardial coronary arteries are associated lesions with hypoplasia of either the right or left ventricle. These patterns will receive attention in the appropriate chapters (see Chapters 43 and 69 ), as will the fistulous connection, which exists as primary lesions in the otherwise normal heart (see Chapter 50 ).
Myocardial Bridging
The major branches of the coronary arteries usually lie within the fibroadipose tissues of either the atrioventricular or interventricular grooves. On occasion, the arteries can be bridged by segments of ventricular myocardium. The reported extent and frequency of such bridges depend on the diligence of the prosector working in the dissecting room. The clinical significance of such bridges has yet to be established.
Developmental Considerations
Much has been learned over the past 3 decades regarding the origin and formation of the coronary arteries. In this respect, the smooth muscle of the walls of the arteries is derived from the epicardial tissues supplied from the so-called proepicardial organ. However, there is ongoing discussion regarding the origin of the coronary arterial endothelial lining, which provides the scaffold for eventual formation of the arteries themselves. Elegant experiments using molecular genetics have shown that the epicardial coronary arteries and those supplying the compact component of the ventricular walls likely have dual origins. Those found within the atrioventricular grooves and those located within the parietal ventricular walls are derived initially by outgrowths from the endothelium of the systemic venous sinus. In contrast, the coronary arteries within the septum and presumably also the anterior interventricular artery are built on endothelium derived from the ventricle itself. It also remains to be determined whether the coronary arterial stems originating from the aortic root sprout from the aorta itself or grow into the valvar sinuses. It used to be thought that the stems grew into the aorta, and recent molecular evidence continues to support that notion. However, evidence is now accruing to suggest that endothelial sprouts do emerge from the aortic trunk, merging with a so-called peritruncal plexus within the epithelial coat of the developing arterial roots. Morphologic evidence is also in favor of the origin of sprouts emerging from the aorta because such vessels are seen in the developing mouse heart prior to the stage at which the coronary arterial orifices have been incorporated into the aortic valvar sinuses ( Fig. 46.13 ). The initial finding of the aortic origin of the coronary arteries distal to the site of the sinutubular junction provides a good explanation for the frequent finding of high origin of the coronary arteries. The process of septation must also be significant in determining the location of the coronary arterial orifices, because it cannot be coincidence that the origin of one coronary artery from the pulmonary trunk is frequent in the setting of aortopulmonary window.
Anomalous Origin of the Left Coronary Artery From the Pulmonary Trunk or Bland-White-Garland Syndrome
Incidence
Anomalous origin of the left coronary artery from the pulmonary trunk (ALCAPT) is the most prevalent form of an anomalous origin of a coronary artery from the pulmonary arterial pathways. The incidence of ALCAPT ranges from 1 in 30,000 to 1 in 300,000 people. It has no discernable heritable pattern, and there is no racial or ethnic predilection to the diagnosis. There is a 3 : 1 male to female predominance of occurrence.
Pathophysiology
In the fetal circulation, the systemic and pulmonary circulation pressures are similar and the oxygen saturations in the main pulmonary artery and aorta are similar, resulting in a normal myocardial oxygen delivery, despite the anomalous coronary origin. After birth, as the pulmonary vascular resistance drops, the myocardial oxygen delivery suffers due to receiving desaturated blood at an insufficient perfusion pressure. This results in progressive myocardial ischemia and ventricular dysfunction.
Initially, myocardial ischemia occurs only during times of increased myocardial oxygen consumption, such as feeding or crying. However, as the pulmonary vascular resistance continues to decrease, flow reversal occurs from the left main coronary artery into the pulmonary trunk in diastole. This results in continued underperfusion of the left ventricular (LV) myocardium, leading to infarction of the LV free wall, and subsequent mitral valve papillary dysfunction with mitral valve regurgitation and LV volume overload.
If there is another cardiac defect present that elevates the pulmonary arterial pressure, such as a large ventricular septal defect, or patency of the arterial duct, there may be adequate coronary perfusion pressure to prevent LV ischemia despite the anomalous origin of the coronary artery. However, upon repair of these defects, with the resultant abrupt decrease in pulmonary arterial pressures, acute LV ischemia can develop, usually with poor outcomes.
In a small number of patients, significant coronary collateralization develops. If this occurs, perfusion of the left coronary artery system is maintained. However, over time, as the pulmonary vascular resistance drops, increased flow occurs from the right coronary system through the left coronary system into the main pulmonary artery. This results in a left-to-right shunt and pulmonary-coronary steal. The left and right coronary arterial systems will progressively dilate. Although the overall amount of left-to-right shunting is relatively small compared with the total cardiac output, it can be a significant portion of the coronary blood flow. If left coronary ostial stenosis is present, it can protect patients from the coronary steal phenomenon. Children with extensive collaterals may have improved survival in infancy but typically have progressive LV dysfunction. In a small number of patients, collateralization is adequate to provide adequate myocardial perfusion, and these patients may escape diagnosis until adulthood.
Clinical Presentation
Infants with ALCAPT typically present with clinical symptoms around 6 to 8 weeks of age, once the pulmonary vascular resistance has dropped. Symptoms of myocardial ischemia and congestive heart failure, including crying and diaphoresis with feeding, tachypnea, poor weight gain, and pallor are present in 85% of infants.
Some patients will not present with symptoms until later in childhood, or even adulthood, likely due to early and adequate coronary artery collateralization. Children can present with a murmur of mitral regurgitation, or chest pain with exertion consistent with ischemia. Adults may present with anginal chest pain, presyncope or syncope, palpitations, or dyspnea on exertion. Patients presenting later in life are at risk for sudden cardiac death, particularly with activity.
On physical exam, infants will typically show signs of congestive heart failure including tachypnea, tachycardia, and hepatomegaly. Due to an enlarged left heart, the point of maximal impulse is frequently prominent and displaced laterally and inferiorly. The first and second heart sounds can be normal, although if pulmonary hypertension is present, the second heart sound will be closely split with a loud P2. An S3 gallop rhythm is commonly present. In infants with significant mitral regurgitation, a blowing holosystolic murmur will be audible, best heard at the apex. In late-presenting older children, adolescents, and adults, signs of congestive heart failure may be present but are less likely. In these patients a continuous murmur may be heard due to continuous retrograde blood flow from the left coronary artery into the pulmonary artery.
Diagnosis
Although a chest x-ray in an infant with ALCAPT typically demonstrates cardiomegaly with or without pulmonary venous congestion, this is not a sensitive or specific finding. The electrocardiogram in infants with ALCAPT can have a classic pattern. It may show an anterolateral infarct pattern with deep Q waves in leads I, aVL, V 5 , and V 6 , poor R wave progression across the precordial leads, and ST segment depression or inversion in the inferior and lateral leads ( Fig. 46.14 ). These electrocardiographic abnormalities should prompt the consideration of ALCAPT in the differential diagnosis of any infant or child in congestive heart failure.
