Congenital Coronary Anomalies

Published on 26/02/2015 by admin

Last modified 22/04/2025

Print this page

This article have been viewed 2286 times

CHAPTER 33 Congenital Coronary Anomalies

Anomalies of the coronary arteries are uncommon, but sometimes can be clinically significant. Most coronary artery anomalies are benign and clinically insignificant; however, some may lead to compromise to coronary flow causing ischemia, heart failure, and death. Clinical presentation depends on the specific anomaly.

Noninvasive imaging has emerged as the preferred way to image coronary anomalies. Electron-beam CT and MR angiography are valuable for the diagnosis of anomalous coronary arteries. More recently, multidetector CT also has been shown to be very useful in the detection and characterization of anomalous coronary arteries. This chapter reviews the appearance of the most commonly encountered coronary anomalies on noninvasive imaging using CT and MRI.

DEFINITION

Anomalous coronary arteries can be grouped into three general categories. Angelini and colleagues ¹ have written one of the most complete works on this subject, and this text can serve as an excellent reference for additional study. Anomalies generally can be divided into three general classifications: (1) anomalies of origin and course (ectopic ostium within proper sinus, ostium outside normal sinus, and absent vessel); (2) anomalies of intrinsic coronary arterial anatomy (congenital stenosis of ostium, congenital aneurysms, and myocardial bridging); and (3) anomalies of coronary termination (fistulas) (Table 33-1).

TABLE 33-1 Classification of Coronary Anomalies

Anomalies of Intrinsic Coronary Arterial Anatomy

Congenital ostial stenosis

Congenital coronary aneurysms

Myocardial bridging

Anomalies of Termination Coronary artery fistula

One of the most commonly encountered anomalies of origin and course is that of a retroaortic circumflex coronary artery that arises from the right sinus of Valsalva. This has an anomalous ectopic ostium (right sinus of Valsalva) and course (retroaortic), but terminates in the usual location (left atrioventricular groove). Myocardial bridging is a commonly encountered anomaly of intrinsic coronary anatomy. Although the artery, which is almost always the left anterior descending (LAD) artery, arises from the usual sinus and travels in the usual course (anterior interventricular groove), but it takes an unusual temporary dip into the myocardium of the anterior wall before re-emerging in the epicardial fat.

Finally, anomalies of coronary termination include coronary artery fistulas. These are coronary arteries that arise from the proper sinus, but eventually terminate in an unusual location. The coronary artery blood flow does not supply the myocardium, but may flow into the pulmonary artery, coronary sinus, cardiac chamber, or superior vena cava. Small fistulas are incidental findings; however, large fistulas may have serious hemodynamic and clinical consequences.

PREVALENCE AND EPIDEMIOLOGY

Congenital anomalies of the coronary arteries affect about 1.3% (range 0.2% to 5.6%) of individuals.²^–¹⁰ Approximately 80% of anomalies are considered benign without significant clinical sequelae; the remaining 20% can potentially cause symptoms, and may be responsible for significant disease.³

We have found a slightly higher prevalence of coronary anomalies than was previously reported. A review of 2087 coronary CT examinations (JP Earls, unpublished data) found an overall prevalence of coronary anomalies of 3.83%. Of those, 54% (or 2.1% of the total) were not previously suspected, whereas 46% (or 1.8% of the total) were either previously known or suspected based on prior imaging studies. One might expect to see anomalies in a larger percentage of clinical cases than one would believe based on epidemiologic studies.

ETIOLOGY AND PATHOPHYSIOLOGY

Coronary anomalies are congenital in origin. In many cases, blood flow to the myocardium remains intact, even in periods of high myocardial oxygen demand, and when no clinical consequences are present. In other cases, the abnormal origin or course leads to compromised blood flow either during exercise or at rest, and symptoms may develop.

The terminology used to describe coronary anomalies is not standardized and sometimes can be confusing. In addition, the actual number of different coronary anomalies is large. The most common anomalies involve variations in the origin or course of the coronary arteries themselves; examples include an artery that arises from the incorrect coronary sinus, which must travel back to its anatomically correct location before terminating in the anatomically correct region of myocardium. In most cases, anomalies are sporadic isolated findings. They may also be associated with other cardiac pathology, however, including valvular lesions, such as a bicuspid aortic valve, or congenital heart disease, such as tetralogy of Fallot or transposition of the great vessels.

MANIFESTATIONS OF DISEASE

Clinical Presentation

Presentation depends greatly on the specific anomaly. Most coronary artery anomalies are benign and never have any clinical symptoms. These are usually detected as incidental findings. Other anomalies are potentially significant and are sometimes ominously termed malignant or potentially lethal; these increase the risk of myocardial ischemia and sudden death because their position or orientation may lead to coronary flow compromise.¹¹^–¹⁵ Although anomalies are uncommon, they can have a substantial impact on premature cardiac morbidity and mortality among young adults. Eckart and associates¹⁶ found coronary anomalies present in more than 30% of sudden nontraumatic deaths in young individuals.

Imaging Indications and Algorithm

Noninvasive imaging has emerged as the preferred way to diagnose and evaluate coronary anomalies. Echocardiography can often detect anomalous origins and even some anomalous courses or, as in the case of larger fistulas, anomalous terminations. Electron-beam CT and MR angiography are useful for the comprehensive diagnosis of anomalous coronary arteries.¹⁷^–²² More recently, multidetector CT has proved to be useful in the detection and characterization of anomalous coronary arteries.²³^–²⁸

IMAGING TECHNIQUE AND FINDINGS

Computed Tomography

Cardiac multidetector CT using contrast-enhanced technique is capable of detecting and characterizing coronary artery anomalies. Most anomalies are incidental findings and are frequently detected when the coronary arteries are being evaluated for atherosclerotic stenoses. The same CT angiographic technique is used when imaging coronary anomalies and atherosclerotic coronary artery disease. This technique is discussed in depth in Chapter 9.

With the exception of anomalous coronary arteries arising from the pulmonary artery, anomalous arteries fill with contrast material at the same time as anatomically normal arteries. Timing of contrast administration and data acquisition for the examination should not be altered. If anomalous origin from the pulmonary artery is suspected, a longer contrast infusion may be appropriate. In situations where the anomalies are seen in conjunction with other cardiac conditions, such as transposition of the great vessels, the amount of imaged anatomy in the z-axis may be increased from the standard heart and aortic root only selection.

Magnetic Resonance Imaging

MRI has been used for a long time to image potential coronary anomalies. It has the advantage of not using ionizing radiation, and has many different pulse sequences to help identify and evaluate the anomalous artery. MRI has been especially used in children and young adults to minimize radiation dose because this population is more susceptible to radiation-induced malignancies owing to their young age. Techniques vary widely and include bright blood and dark blood sequences, contrast-enhanced and non–contrast-enhanced sequences, and breath-hold and non–breath-hold sequences. No single technique has yet emerged as the dominant coronary MRI technique for coronary analysis. MRI sometimes can be less reliable, however, than its newer competitor, multidetector CT. MRI does not expose patients to the higher risks of ionizing radiation and of iodinated contrast agents. The relatively small amount of radiation exposure and of need for an intravenous catheter are particular advantages for imaging children.

DIFFERENTIAL DIAGNOSIS

Anomalies of Origin and Course

Anomalous Origin of a Coronary Artery from the Opposite Sinus of Valsalva

One of the most commonly encountered potentially serious anomalies involves the anomalous origination of a coronary artery from the opposite sinus of Valsalva. Either the right coronary artery (RCA) or the left coronary artery (LCA) can arise from the opposite sinus, and then traverse across the heart to resume a normal position. Alternatively, a single branch of the LCA, the LAD artery, or the left circumflex artery can arise from the opposite sinus, whereas the remainder of the LCA may arise from the correct sinus.

There are several potential courses for an anomalous LCA arising from the right sinus of Valsalva or the RCA (Fig. 33-1). Diagnosis of the exact course is important because it determines if intervention is necessary. There are four possible pathways for the anomalous LCA: (1) between the aortic root and the pulmonary artery (interarterial course), (2) a transseptal (intraseptal or subpulmonic) course, (3) anterior to the right ventricular outflow tract (anterior or prepulmonic course), and (4) posterior to the aortic root (retroaortic course). Although the anterior, posterior, and septal (subpulmonic) courses are benign, an interarterial course carries a high risk for sudden cardiac death.²⁹^,³⁰

FIGURE 33-1 There are four possible pathways for the anomalous LCA: (1) an interarterial course between the aortic root and the pulmonary artery, (2) a septal course through the myocardium below the pulmonary artery, (3) an anterior or prepulmonic course anterior to the right ventricular outflow tract, and (4) a retroaortic or posterior course behind the aortic root.

Axial reconstructions from a multidetector CT coronary angiogram can depict the anatomic course. The exact position and course of the anomalous artery can be viewed in relation to the aortic root and pulmonary artery (Fig. 33-2). The LCA arises from the right sinus of Valsalva or directly from the RCA in 0.10% of patients, and an interarterial course is present in approximately 75% of these patients.³¹

FIGURE 33-2 Axial reconstruction from a multidetector CT coronary angiogram confirms that the anomalous LCA arises with the RCA from the right sinus of Valsalva and has an interarterial course, passing between the aorta (Ao) and pulmonary artery (PA).

Three-dimensional volume rendered multidetector CT images of the coronary arteries and aortic root can also be helpful in depicting the course and anatomic relationships. An anomalous coronary artery originating from the opposite sinus of Valsalva can cause syncope, myocardial infarction, and sudden death in the absence of critical, fixed stenosis. Patients with an anomalous LCA that takes an interarterial course have a high risk for sudden cardiac death because of the acute angle of the ostium, the stretch of the intramural segment of the anomalous artery, or the compression between the commissures of the right and left coronary cusps.¹^,³¹ This anomalous LCA may narrow the origin or proximal aspect of the vessel and limit flow. An anomalous interarterial coronary artery is frequently an underlying cause for sudden death in young athletes. Often, MRI can also show an anomalous coronary artery with an interarterial course (Fig. 33-3).

FIGURE 33-3 MRI of an anomalous RCA that takes an interarterial course. A, Volume rendered view of a gadolinium-enhanced three-dimensional MR angiogram depicts the anomalous RCA arising from a near common origin with the LCA from the left sinus of Valsalva. B, Double inversion recovery fast spin-echo black blood image depicts the anomalous interarterial RCA (arrow) as a low signal intensity structure passing between the aorta (Ao) and pulmonary artery (PA).

The other three types of anomalous coronary artery originating from the opposite sinus of Valsalva have predominately benign clinical outcomes. Anomalous coronary arteries originating from the opposite sinus of Valsalva can have an intraseptal (intramyocardial) course (Fig. 33-4). In this anomaly, the proximal portion of the anomalous coronary artery is completely surrounded by the gray myocardium of the interventricular septum, and is believed to be “protected” from possible compression as seen more typically with the interarterial course. Care must be taken, however, because a portion of the anomalous coronary, especially the initial proximal segment, may be extracardiac, in which case it assumes the same risks noted for the anomalous interarterial course. The intraseptal pathway is mostly located within the upper, anterior interventricular septum. Frequently, septal branches can be seen to arise from the anomalous vessel, a distinction that may help differentiate an interarterial course from an intraseptal course on conventional angiography.

FIGURE 33-4 A, Maximum intensity projection image of an anomalous LCA arising from the right sinus of Valsalva and taking an intraseptal course. B, On a curved multiplanar reconstruction image, the proximal portion of the LCA is completely surrounded by the gray myocardium of the interventricular septum. This anomalous pathway is mostly located within the upper, anterior interventricular septum.

In cases with an anomalous LCA or LAD artery with an anterior course, the anomalous LCA or LAD artery arises from the proximal RCA and takes a course anterior to the pulmonary artery (Fig. 33-5). Because the anomalous vessel is long and is associated primarily with the low-pressure pulmonary outflow tract, it does not get compressed or stretched as does the interarterial course of an anomalous artery arising from the opposite coronary sinus. It is considered a benign anomaly without significant clinical sequelae. This particular anomaly is commonly seen in patients with tetralogy of Fallot. An anterior course may also be seen with an anomalous RCA that arises from the LCA or LAD artery.

FIGURE 33-5 An anomalous LCA arises from the proximal RCA and takes a course anterior to the pulmonary artery (PA).

The fourth variant of anomalous coronary artery originating from the opposite sinus of Valsalva involves a course posterior to the aorta (i.e., retroaortic course) (Fig. 33-6). In this case, an anomalous circumflex coronary artery arises with the RCA from the right sinus of Valsalva. The retroaortic course is the most common pathway for an anomalous origin of a coronary artery from the opposite sinus of Valsalva. The retroaortic left circumflex artery is seen in 0.1% to 0.9% of the population.¹

FIGURE 33-6 Volume rendered view depicts an anomalous circumflex coronary artery (arrow) arising from the RCA and passing posterior to the aortic root. The retroaortic course is the most common pathway for an anomalous origin of a coronary artery from the opposite sinus of Valsalva.

Anomalous Origin of a Coronary Artery from the Pulmonary Artery

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a very serious anomaly, reported in 1 of every 300,000 live births.³² Most patients become symptomatic in infancy and early childhood. Ninety percent of untreated infants die before 1 year of age, and only a few patients survive to adulthood.³³ In ALCAPA, the LCA arises from the pulmonary artery (Fig. 33-7), and the RCA arises normally from the aorta; this is also known as Bland-White-Garland syndrome.¹ ALCAPA is usually an isolated anomaly, but rarely it has been described with patent ductus arteriosus, ventricular septal defect, tetralogy of Fallot, and coarctation of the aorta.

FIGURE 33-7 A, Curved multiplanar reconstruction image depicts the origin of the left circumflex (arrow) from the left pulmonary artery (LPA). B, Posterior view of a three-dimensional volume rendered multidetector CT coronary angiogram provides a better three-dimensional view of the anomalous dominant left circumflex (arrow) and LPA.

In patients with ALCAPA, initially myocardial ischemia is transient; however, increases in myocardial oxygen consumption lead to infarction, dysfunction, and mitral insufficiency. Collateral circulations between the right and left coronary systems develop, and LCA flow eventually reverses and enters the pulmonic trunk because of the low pulmonary vascular resistance (coronary steal phenomenon). Eventually, the combination of left ventricular dysfunction and significant mitral valve insufficiency leads to congestive heart failure.

Current surgical treatment for ALCAPA is directed at establishing revascularization by recreating a two–coronary artery system. This is done via a number of methods: a left subclavian artery–coronary artery anastomosis, a saphenous vein bypass graft, Takeuchi procedure (creation of an intrapulmonary tunnel), or direct reimplantation. After surgery, most patients experience normalization of left ventricular function, improving long-term survival.³² An anomalous origin of the RCA from the pulmonary artery may also occur, but with ischemic complications affecting the RCA versus LCA vascular distribution.

Anomalous Coronary Artery Arising from the Noncoronary Sinus

Either the RCA or the LCA may arise from the noncoronary sinus of Valsalva (Fig. 33-8). Both of these anomalies are rare, and in an otherwise normal heart, they usually have no clinical relevance. These anomalies may also be seen with transposition of the great vessels.³⁴ Although of minimal clinical importance, documentation of the anomaly would be useful before conventional coronary angiography or intervention. As patients age, the aortic root can rotate clockwise, causing the normal LCA origin to turn more posterior than usual. One needs to be careful not to misdiagnose anomalous LCA arising from a noncoronary sinus in this situation.

FIGURE 33-8 Multidetector CT depicts an anomalous LCA (arrow) arising from the noncoronary sinus of Valsalva (asterisk).

High Origin of a Coronary Artery

A high origin of a coronary artery refers to origin outside of the coronary sinus (Fig. 33-9), above the junctional zone between its sinus and the tubular part of the ascending aorta. High coronary ostia, located above the sinotubular junction, have been reported in 6% of adult hearts.³⁵ A high origin of a coronary artery is generally not related to hemodynamic or clinical problems; however, it may lead to difficulty in cannulating the artery during conventional coronary arteriography. Intra-arterial cannulation of an RCA with a high origin, especially when it is above the right sinus of Valsalva, can be particularly difficult.

FIGURE 33-9 Volume rendered view from a multidetector CT scan depicts high origins of the RCA and LCA; both arise from the ascending aorta above the right and left sinuses of Valsalva.

Multiple Ostia

Another commonly encountered benign anomaly is absence of the left main coronary artery resulting in separate origins of the LAD artery and left circumflex artery (Fig. 33-10). Separate origins of the LCA and left circumflex artery are reported in a few (0.41%) patients and are unrelated to other anomalies or cardiac disease.³⁶ The clinical relevance of separate origins of the LAD artery and left circumflex artery is limited because there are no known adverse hemodynamic effects. This anomaly may present difficulty for the angiographer because multiple ostia need to be recognized and require separate cannulation during selective diagnostic catheterization studies. Separate origins may have some protective effects because this configuration allows for alternative collateral sources in patients with proximal coronary stenoses.³⁴

FIGURE 33-10 Three-dimensional volume rendered multidetector CT coronary angiogram depicts absence of the left main coronary artery and separate origins of the LAD artery (thick arrow) and left circumflex (thin arrow) arteries. This anomaly may present difficulty for the angiographer because multiple ostia need to be recognized and require separate cannulation during diagnostic catheterization examinations.

Arterial Duplication

Arterial duplication is another form of coronary anomaly and often involves the LAD artery (Fig. 33-11). Clinically this anomaly had been termed duplication of the LAD artery, and it is seen in 0.13% to 1% of the general population.³⁷ This anomaly consists of a short LAD artery, which courses and terminates in the anterior interventricular sulcus, and a long LAD artery, which originates from either the LAD artery or the RCA and enters the distal interventricular sulcus and courses to the apex.³⁷ Because the LAD artery is frequently bypassed surgically, it is important to recognize this anomaly before surgical revascularization so that the surgical arteriotomy is correctly placed.³⁷

FIGURE 33-11 Multidetector CT coronary angiogram shows that the LAD artery has a dual origin. The proximal portion arises normally from the left main coronary artery. The mid to distal portion of the LAD artery arises from the RCA via a branch (arrow) that traverses anterior to the pulmonary outflow tract.

Single Coronary Artery

A single coronary artery (Fig. 33-12) is a rare anomaly in which only one coronary artery arises from the aortic trunk by a single ostium. The artery supplies the blood to the entire heart. The presence of a single coronary artery is rare, reported in approximately 0.024% to 0.066% of the population.¹^,³⁸ A single coronary artery has many different patterns of distribution. It may follow the pattern of a normal artery, divide into two branches with distributions of the RCA and the LCA, or have a distribution different from that of the normal coronary arterial tree.³⁹ Single coronary artery is a very heterogeneous group of anomalies in which the single artery can arise from the right, left, or noncoronary sinus of Valsalva, and the pathways of the branches can vary greatly, taking retrocardiac, retroaortic, interarterial, intraseptal, and anterior courses.

FIGURE 33-12 A single coronary artery arises from the right sinus of Valsalva, with associated retroaortic circumflex artery, and interarterial (thin arrow) and anterior (thick arrow) courses of a duplicated LAD artery.

Anomalies of Intrinsic Coronary Arterial Anatomy

Congenital Ostial Stenosis

Coronary arteries may have an ostial stenosis that is not due to atherosclerosis or other type of acquired disease. Congenital ostial stenoses are due to a membrane or fibrotic ridge.¹ This membrane or ridge is sometimes found with anomalous coronary arteries, and is believed to be due to the tangential orientation of the anomalous artery as it passes through the aortic wall. Ostial stenoses may be present in some cases where the RCA arises ectopically from the left sinus of Valsalva and runs in an interarterial path (Fig. 33-13).

FIGURE 33-13 Curved multiplanar reconstruction of an anomalous RCA, arising from the left sinus of Valsalva and taking an interarterial course. The proximal portion of the RCA is significantly narrowed consistent with congenital ostial stenosis. PA, pulmonary artery.

Congenital Coronary Aneurysms

Ectasia, or aneurysm formation, may be localized to a single coronary segment or can involve the coronaries diffusely. Patients with either focal or diffuse coronary ectasia, not related to atherosclerosis, have abnormal arterial walls, with medial degeneration, intimal thickening, and eventual ulceration and mural thrombus formation.⁴⁰ Congenital coronary aneurysms are often associated with Kawasaki disease (Fig. 33-14).

FIGURE 33-14 Focal aneurysms (arrows) of the proximal RCA and LCA in a 14-year-old boy with a history of Kawasaki disease.

Myocardial Bridging

Normal coronary arteries traverse the epicardial fat before entering the myocardium. In complete myocardial bridging, a short segment of the artery, known as a tunneled segment, passes into and through the myocardium for a short segment before re-entering the epicardial fat. It then branches normally and terminates within the myocardium (Figs. 33-15 and 33-16). Complete myocardial bridging is seen in 20% of asymptomatic patients and is a very rare cause of ischemia secondary to spasm. In incomplete myocardial bridging, the involved artery extends down to and touches the myocardium, but does not completely enter before extending back up into the myocardium.

FIGURE 33-15 Diagram depicts a normal coronary artery (CA) and complete and incomplete myocardial bridging. Normal coronary arteries traverse the epicardial fat before entering the myocardium. In complete myocardial bridging, a short segment of the artery, known as a tunneled segment, passes into and through the myocardium for a short segment before re-entering the epicardial fat. It then branches normally and terminates within the myocardium. LV, left ventricle; RV, right ventricle.

(Redrawn from Earls JP. Coronary artery anomalies. In Narula J, Budoff MJ, Achenbach SS [eds]. Atlas of Cardiovascular Computed Tomography. New York, Springer, 2007.)

FIGURE 33-16 Curved multiplanar reconstruction of the LAD artery in a patient with complete myocardial bridging shows that the artery enters the myocardium for a short segment then re-enters the epicardial fat.

Myocardial bridging typically involves the middle portion of the LAD artery, but the circumflex artery, diagonal arteries, and RCA are occasionally involved.⁴¹ The prevalence of myocardial bridging varies greatly in reported series, ranging from 0.5% to 2.5% on angiography examinations to 15% to 85% at pathologic analysis.⁴¹ Multidetector CT coronary angiography depicts the intramyocardial path of the involved coronary arterial segment. Although most patients with myocardial bridging are asymptomatic, in rare cases myocardial bridging is responsible for angina pectoris, myocardial infarction, life-threatening arrhythmias, or death.⁴¹

Anomalies of Termination: Coronary Artery Fistula

A coronary fistula is an abnormal connection between a coronary artery and the pulmonary artery (Fig. 33-17), coronary sinus, cardiac chamber, or superior vena cava. Fistulas are present in approximately 0.1% to 0.2% of patients at coronary angiography.⁴² Small fistulas are often incidental findings; however, large fistulas have serious hemodynamic and clinical consequences. Fistulas represent a left-to-right or a left-to-left shunt, depending on where they communicate, and they result in dilation of the coronary artery to varying degrees, depending on the shunt volume. Myocardial ischemia may develop in the portion of the myocardium supplied by the abnormally connecting coronary artery. The right ventricle is the most common site of drainage (45% of cases), followed by the right atrium (25%) and the pulmonary artery (15%).⁴³