DOI: 10.1148/rg.262055068
RadioGraphics 2006;26:317-333
© RSNA, 2006
Coronary Artery Anomalies: Classification and ECG-gated Multi–Detector Row CT Findings with Angiographic Correlation1
So Yeon Kim, MD,
Joon Beom Seo, MD,
Kyung-Hyun Do, MD,
Jeong-Nam Heo, MD,
Jin Seong Lee, MD,
Jae-Woo Song, MD,
Yeon Hyeon Choe, MD,
Tae Hoon Kim, MD,
Hwan Seok Yong, MD,
Sang Il Choi, MD,
Koun-Sik Song, MD and
Tae-Hwan Lim, MD
1 From the Department of Radiology and the Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 388-1, Pungnap-2 dong, Songpa-ku, Seoul 138-736, Korea (S.Y.K., J.B.S., K.H.D., J.N.H., J.S.L., J.W.S., K.S.S., T.H.L.); the Department of Radiology, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea (Y.H.C.); the Department of Radiology, Yongdong Severance Hospital, Yonsei University College of Medicine, Seoul, Korea (T.H.K.); the Department of Radiology, Korea University College of Medicine, Seoul, Korea (H.S.Y.); and the Department of Radiology, Seoul National University Bundang Hospital, Seongnam, Korea (S.I.C.). Recipient of a Magna Cum Laude award for an education exhibit at the 2004 RSNA Annual Meeting. Received March 22, 2005; revision requested May 9 and received June 24; accepted June 27. All authors have no financial relationships to disclose.
Address correspondence to J.B.S. (e-mail: seojb{at}amc.seoul.kr).
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Abstract
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Congenital abnormalities of the coronary arteries are an uncommon but important cause of chest pain and, in some cases of hemodynamically significant abnormalities, sudden cardiac death. For several decades, premorbid diagnosis of coronary artery anomalies has been made with conventional angiography. However, this imaging technique has limitations due to its projectional and invasive nature. The recent development of electrocardiographically (ECG)–gated multi–detector row computed tomography (CT) allows accurate and noninvasive depiction of coronary artery anomalies of origin, course, and termination. Multi–detector row CT is superior to conventional angiography in delineating the ostial origin and proximal path of an anomalous coronary artery. Familiarity with the CT appearances of various coronary artery anomalies and an understanding of the clinical significance of these anomalies are essential in making a correct diagnosis and planning patient treatment.
© RSNA, 2006
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LEARNING OBJECTIVES FOR TEST 1
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After reading this article and taking the test, the reader will be able to:- Discuss the classification of coronary artery anomalies.
- Identify hemodynamically significant coronary artery anomalies.
- Describe the ECG-gated multi–detector row CT appearances of various coronary artery anomalies in correlation with conventional coronary angiographic findings.
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Introduction
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Computed tomography (CT) of the coronary arteries moved into the diagnostic realm with the introduction of multi–detector row CT and the development of electrocardiographically (ECG)–synchronized scanning and reconstruction techniques (1). Multi–detector row CT, with its faster volume coverage and higher spatial and temporal resolution, allows imaging of the coronary arteries and detection of related diseases (2). With four-and 16-section multi–detector row CT scanners, the sensitivity of noninvasive CT angiography for the detection of hemodynamically significant coronary artery stenosis within the proximal coronary arteries ranges between 80% and 90% (3–5). Moreover, 16-section multi–detector row CT is now accepted as an accurate diagnostic tool for defining coronary artery anomalies. It has been reported that multi–detector row CT may be superior to conventional angiography in defining the ostial origin and proximal path of anomalous coronary branches (3).
In this article, we review the normal anatomy of the coronary artery system. We also discuss and illustrate various coronary artery anomalies in terms of clinical importance, type (anomalies of origin, course, and termination), and manifestations at multi–detector row CT in correlation with angiographic appearances. In addition, we briefly discuss congenital heart diseases that may be associated with coronary artery anomalies.
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Normal Anatomy of the Coronary Artery System
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The four main coronary arteries evaluated at CT are the right coronary artery (RCA), the left main coronary artery (LCA), the left anterior descending (LAD) artery, and the left circumflex (LCx) artery. A "circle and half-loop" model has been introduced to illustrate the anatomic relationships among these arteries. The circle consists of the RCA and the LCx artery, whereas the half loop is formed by the LAD artery and the posterior descending artery (PDA) (Fig 1) (6).
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Figure 1. Diagrams illustrate the coronary artery anatomy (circle and half-loop model). The circle consists of the RCA and the LCx artery. The half loop is formed by the LAD artery and the PDA.
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Whichever artery crosses the crux of the heart and gives off the posterior descending branches is considered to be the dominant coronary artery. In approximately 85% of individuals, the RCA crosses the posterior interventricular groove and gives rise to the posterior descending branches (right dominance); in 7%–8%, the LCx artery crosses the interventricular groove and gives rise to branches to the posterior right ventricular surface (left dominance); and in the remaining 7%–8%, the inferior interventricular septum is perfused by branches from both the distal RCA and the distal LCx artery (codominance) (7).
The RCA arises from the anterior right coronary sinus somewhat inferior to the origin of the LCA. The RCA passes to the right of and posterior to the pulmonary artery and then downward in the right atrioventricular groove toward the posterior interventricular septum. In more than 50% of individuals, the first branch of the RCA is the conus artery, unless it (the RCA) has a separate origin directly from the right coronary sinus (7). The second branches usually consist of the sinoatrial node artery and several anterior branches that supply the free wall of the right ventricle. The branch to the right ventricle at the junction of the middle and distal RCA is called the acute marginal branch. The distal RCA divides into the PDA and posterior left ventricular branches in a right dominant anatomy (Fig 2) (7,8).
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Figure 2a. Normal ECG-gated multi–detector row CT anatomy of the RCA and its branches. (a) Oblique volume-rendered (VR) image of the top of the heart shows the RCA (arrow) arising from the right sinus of Valsalva and coursing in the right atrioventricular groove toward the posterior interventricular septum. A = aorta, PA = pulmonary artery. The conus artery and the sinoatrial node artery were too small to be seen in this case. (b) Lateral oblique VR image shows the caudal course of the proximal RCA (arrow), which gives off an acute marginal branch (arrowheads) to the right ventricle. (c) Posterior oblique VR image shows that the distal RCA divides into the PDA (straight arrow) and posterior left ventricular branches (arrowheads). The PDA courses in the posterior interventricular groove, parallel to the middle cardiac vein (curved arrow).
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Figure 2b. Normal ECG-gated multi–detector row CT anatomy of the RCA and its branches. (a) Oblique volume-rendered (VR) image of the top of the heart shows the RCA (arrow) arising from the right sinus of Valsalva and coursing in the right atrioventricular groove toward the posterior interventricular septum. A = aorta, PA = pulmonary artery. The conus artery and the sinoatrial node artery were too small to be seen in this case. (b) Lateral oblique VR image shows the caudal course of the proximal RCA (arrow), which gives off an acute marginal branch (arrowheads) to the right ventricle. (c) Posterior oblique VR image shows that the distal RCA divides into the PDA (straight arrow) and posterior left ventricular branches (arrowheads). The PDA courses in the posterior interventricular groove, parallel to the middle cardiac vein (curved arrow).
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Figure 2c. Normal ECG-gated multi–detector row CT anatomy of the RCA and its branches. (a) Oblique volume-rendered (VR) image of the top of the heart shows the RCA (arrow) arising from the right sinus of Valsalva and coursing in the right atrioventricular groove toward the posterior interventricular septum. A = aorta, PA = pulmonary artery. The conus artery and the sinoatrial node artery were too small to be seen in this case. (b) Lateral oblique VR image shows the caudal course of the proximal RCA (arrow), which gives off an acute marginal branch (arrowheads) to the right ventricle. (c) Posterior oblique VR image shows that the distal RCA divides into the PDA (straight arrow) and posterior left ventricular branches (arrowheads). The PDA courses in the posterior interventricular groove, parallel to the middle cardiac vein (curved arrow).
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The LCA arises from the left posterior coronary sinus, is 5–10 mm long, and does not vary in diameter. The LCA passes to the left of and posterior to the pulmonary trunk and bifurcates into the LAD and LCx arteries. Occasionally, the LCA trifurcates into the LAD and LCx arteries and the ramus intermedius. The ramus intermedius has a course similar to that of the first diagonal branch of the LAD artery to the anterior left ventricle. The LAD artery passes to the left of the pulmonary trunk and turns anteriorly to course in the anterior interventricular groove toward the apex. It provides the diagonal branches to the anterior free wall of the left ventricle and the septal branches to the anterior interventricular septum. The LCx artery courses in the left atrioventricular groove and gives off obtuse marginal branches to the lateral left ventricle. In a left dominant or codominant anatomy, the LCx artery gives rise to the PDA or posterior left ventricular branches (Fig 3) (7–10).
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Figure 3a. Normal ECG-gated multi–detector row CT anatomy of the LCA and its branches. A = aorta, PA = pulmonary artery. (a) Oblique VR image of the top of the heart shows the LCA (curved arrow) arising from the left sinus of Valsalva and trifurcating into the LAD artery (thin straight arrow), the LCx artery (thick straight arrow), and the ramus intermedius (arrowhead), which takes a course similar to that of the usual first diagonal branch. The LAD artery then gives rise to diagonal branches (short arrows) to the anterior free wall of the left ventricle. (b, c) Anterior (b) and posterior (c) oblique VR images show that the LAD artery (long thin arrows in b, white arrows in c) courses along the anterior interventricular groove, and that the LCx artery (long thick arrow in b, large black arrow in c) courses in the left arterioventricular groove. Obtuse marginal branches (arrowheads) and diagonal branches (short arrows) are also seen.
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Figure 3b. Normal ECG-gated multi–detector row CT anatomy of the LCA and its branches. A = aorta, PA = pulmonary artery. (a) Oblique VR image of the top of the heart shows the LCA (curved arrow) arising from the left sinus of Valsalva and trifurcating into the LAD artery (thin straight arrow), the LCx artery (thick straight arrow), and the ramus intermedius (arrowhead), which takes a course similar to that of the usual first diagonal branch. The LAD artery then gives rise to diagonal branches (short arrows) to the anterior free wall of the left ventricle. (b, c) Anterior (b) and posterior (c) oblique VR images show that the LAD artery (long thin arrows in b, white arrows in c) courses along the anterior interventricular groove, and that the LCx artery (long thick arrow in b, large black arrow in c) courses in the left arterioventricular groove. Obtuse marginal branches (arrowheads) and diagonal branches (short arrows) are also seen.
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Figure 3c. Normal ECG-gated multi–detector row CT anatomy of the LCA and its branches. A = aorta, PA = pulmonary artery. (a) Oblique VR image of the top of the heart shows the LCA (curved arrow) arising from the left sinus of Valsalva and trifurcating into the LAD artery (thin straight arrow), the LCx artery (thick straight arrow), and the ramus intermedius (arrowhead), which takes a course similar to that of the usual first diagonal branch. The LAD artery then gives rise to diagonal branches (short arrows) to the anterior free wall of the left ventricle. (b, c) Anterior (b) and posterior (c) oblique VR images show that the LAD artery (long thin arrows in b, white arrows in c) courses along the anterior interventricular groove, and that the LCx artery (long thick arrow in b, large black arrow in c) courses in the left arterioventricular groove. Obtuse marginal branches (arrowheads) and diagonal branches (short arrows) are also seen.
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Clinical Importance of Coronary Artery Anomalies
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Anomalies of the coronary arteries may be found incidentally in 0.3%–1% of healthy individuals (11). For several decades, premorbid diagnosis of coronary artery anomalies was made with angiography. However, it was recently reported that, among patients with anomalous coronary arteries identified consensually with 16-section multi–detector row CT, conventional angiographic findings alone allowed correct identification of the abnormalities in only 53% of cases (3). The reason for this discrepancy may be that coronary artery anomalies are very difficult to visualize at angiography, and even if they are visualized, their course may be delineated inaccurately.
Although coronary artery anomalies are far less common than acquired coronary artery disease, their impact on premature cardiac morbidity and mortality among young adults is not trivial. In a study by Eckart et al (12) of 126 nontraumatic sudden deaths in young adults, cardiac abnormality was found in 64 cases (51%), with coronary artery abnormalities being the most common cardiac abnormality (39 of 64 patients [61%]).
In this article, we have classified the coronary artery anomalies into anomalies of origin, anomalies of course, and anomalies of termination, with use of a modified version of a classification system developed by Greenberg et al (13) (Table). Coronary artery anomalies may also be classified as hemodynamically either significant or insignificant. Hemodynamically significant anomalies of the coronary arteries are characterized by abnormalities of myocardial perfusion, which lead to an increased risk of myocardial ischemia or sudden death (7). These anomalies include an anomalous origin of either the LCA or the RCA from the pulmonary artery, an anomalous course between the pulmonary artery and the aorta (interarterial) of either the RCA arising from the left sinus of Valsalva or the LCA arising from the right sinus of Valsalva, occasional myocardial bridging, and congenital coronary artery fistula (Table).
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Types of Coronary Artery Anomalies
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Anomalies of Origin
High Takeoff.—
"High takeoff" refers to the origin of either the RCA or the LCA at a point above the junctional zone between its sinus and the tubular part of the ascending aorta (Fig 4). Vlodaver et al (14) reported that both coronary ostia were situated above the sinotubular junction in 6% of randomly selected adult hearts. High take-off of the coronary arteries usually presents no major clinical problems, but it may cause difficulty in cannulating the vessels during coronary arteriography. Selective intubation of the coronary artery may be extremely difficult, especially when the RCA is anomalously located high over the left coronary sinus (9).
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Figure 4a. High takeoff of the RCA in a 55-year-old man. On coronal oblique VR (a) and curved maximum-intensity-projection (MIP) (b) images, the RCA demonstrates a high take-off (arrow) above the sinotubular junction. Atherosclerotic change of the RCA with calcified plaque is also demonstrated.
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Figure 4b. High takeoff of the RCA in a 55-year-old man. On coronal oblique VR (a) and curved maximum-intensity-projection (MIP) (b) images, the RCA demonstrates a high take-off (arrow) above the sinotubular junction. Atherosclerotic change of the RCA with calcified plaque is also demonstrated.
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Multiple Ostia.—
In multiple ostia, typically either the RCA and the conus branch arise separately (Fig 5), or the LAD and LCx arteries arise separately with no LCA (Fig 6). An aberrant conus artery arising separately from the RCA is particularly at risk for injury from ventriculostomy or other maneuvers performed during heart surgery (8). Separate ostia of the LCA and LCx artery may occur in a small percentage (0.41%) of individuals with otherwise normal anatomy (15). Although multiple ostia represent a technical difficulty for the angiographer, they may also allow alternate collateral sources in patients with proximal coronary artery disease (13).
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Figure 5. Multiple ostia with separate origins of the RCA and conus branch in a 60-year-old man. Coronal oblique MIP image shows separate ostia of the RCA (curved arrow) and conus branch (straight arrow) from the right coronary sinus.
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Figure 6a. Multiple ostia with separate origins of the LAD and LCx arteries in a 50-year-old man. Coronal oblique MIP image (a) and oblique VR image of the top of the heart (b) show separate ostia of the LAD (straight arrow) and LCx (curved arrow) arteries. Intimal calcification at the os of the LAD artery is also demonstrated. A = aorta, PA = pulmonary artery.
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Figure 6b. Multiple ostia with separate origins of the LAD and LCx arteries in a 50-year-old man. Coronal oblique MIP image (a) and oblique VR image of the top of the heart (b) show separate ostia of the LAD (straight arrow) and LCx (curved arrow) arteries. Intimal calcification at the os of the LAD artery is also demonstrated. A = aorta, PA = pulmonary artery.
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Single Coronary Artery.—
In the anomalous situation of a single coronary artery, only one coronary artery arises with a single ostium from the aortic trunk (Figs 7, 8). This is an extremely rare congenital anomaly that is seen in only 0.0024%–0.044% of the population (16). A single coronary artery may either follow the pattern of a normal RCA or LCA, divide into two branches with distributions of the RCA and LCA, or have a distribution different from that of the normal coronary arterial tree (17).
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Figure 7a. Single coronary artery in a 55-year-old man. (a) Oblique VR image shows an anomalous origin for the RCA (curved arrow), which arises from the LAD artery (straight arrow) and courses anterior to the pulmonary artery (PA). A = aorta. (b) Coronary angiogram shows the anomalous origin of the hypoplastic RCA (curved arrow) from the LAD artery (straight arrow).
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Figure 7b. Single coronary artery in a 55-year-old man. (a) Oblique VR image shows an anomalous origin for the RCA (curved arrow), which arises from the LAD artery (straight arrow) and courses anterior to the pulmonary artery (PA). A = aorta. (b) Coronary angiogram shows the anomalous origin of the hypoplastic RCA (curved arrow) from the LAD artery (straight arrow).
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Figure 8a. Single coronary artery in an 80-year-old man. (a) Oblique VR image of the top of the heart shows only one coronary artery arising from the left coronary sinus (arrowhead). Note that the RCA (arrow) courses between the aorta (A) and the pulmonary artery (PA). (b) On a sagittal oblique VR image, the single coronary artery demonstrates a high takeoff (arrowhead) above the sinotubular junction. A = aorta, PA = pulmonary artery.
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Figure 8b. Single coronary artery in an 80-year-old man. (a) Oblique VR image of the top of the heart shows only one coronary artery arising from the left coronary sinus (arrowhead). Note that the RCA (arrow) courses between the aorta (A) and the pulmonary artery (PA). (b) On a sagittal oblique VR image, the single coronary artery demonstrates a high takeoff (arrowhead) above the sinotubular junction. A = aorta, PA = pulmonary artery.
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Although a single coronary artery may be compatible with a normal life expectancy, patients are at increased risk for sudden death if a major coronary branch crosses between the pulmonary artery and the aorta. In addition, proximal stenosis of a single coronary artery may be devastating if there is an inability to develop collateral channels (13).
Anomalous Origin of the Coronary Artery from the Pulmonary Artery.—
Anomalous origin of the coronary artery from the pulmonary artery (ALCAPA) is one of the most serious congenital coronary artery anomalies. It has an estimated prevalence of one in 300,000 live births (18). Most affected patients show symptoms in infancy and early childhood. Approximately 90% of untreated infants die in the 1st year of life, and only a few patients survive to adulthood (19). In the most common form of this disease, the LCA arises from the pulmonary artery and the RCA arises normally from the aorta (Bland-White-Garland syndrome) (Fig 9) (20). Coronary angiography usually helps confirm the diagnosis of ALCAPA and demonstrates collateral circulation between the RCA and LCA and a coronary "steal" phenomenon into the pulmonary artery (21). Treatment of ALCAPA consists of re-creation of dual coronary perfusion. In infantile type ALCAPA, either (a) direct reimplantation of the anomalous LCA into the aorta or (b) creation of an intrapulmonary conduit from the left coronary ostia to the aorta (Takeuchi procedure) may be used. In adult type ALCAPA, ligation of the LCA from the pulmonary artery, combined with coronary artery bypass grafting with use of the internal mammary artery or the saphenous vein, may be performed (18).
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Figure 9a. Bland-White-Garland syndrome in a 29-year-old woman. A = aorta, PA = pulmonary artery. (a) Preoperative anterior oblique VR image shows a dilated RCA (arrow) and the LAD artery with multiple collateral vessels at the right ventricular wall (arrowheads). (b, c) Preoperative VR images (cardiac chambers removed with manual editing) clearly demonstrate the anomalous origin of the LCA (arrow in b, straight arrow in c) from the pulmonary trunk, along with multiple collateral vessels within the interventricular septum (arrowheads in b) and the dilated RCA (curved arrow in c). (d, e) Postoperative VR images, obtained after ligation of the original os of the LCA from the pulmonary trunk and creation of an anastomosis between the left internal mammary artery (short straight arrows) and the LCA (long straight arrow), demonstrate a decrease in the size of the RCA (curved arrow) and markedly diminished collateral vessels in the interventricular septum and right ventricular wall (*).
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Figure 9b. Bland-White-Garland syndrome in a 29-year-old woman. A = aorta, PA = pulmonary artery. (a) Preoperative anterior oblique VR image shows a dilated RCA (arrow) and the LAD artery with multiple collateral vessels at the right ventricular wall (arrowheads). (b, c) Preoperative VR images (cardiac chambers removed with manual editing) clearly demonstrate the anomalous origin of the LCA (arrow in b, straight arrow in c) from the pulmonary trunk, along with multiple collateral vessels within the interventricular septum (arrowheads in b) and the dilated RCA (curved arrow in c). (d, e) Postoperative VR images, obtained after ligation of the original os of the LCA from the pulmonary trunk and creation of an anastomosis between the left internal mammary artery (short straight arrows) and the LCA (long straight arrow), demonstrate a decrease in the size of the RCA (curved arrow) and markedly diminished collateral vessels in the interventricular septum and right ventricular wall (*).
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Figure 9c. Bland-White-Garland syndrome in a 29-year-old woman. A = aorta, PA = pulmonary artery. (a) Preoperative anterior oblique VR image shows a dilated RCA (arrow) and the LAD artery with multiple collateral vessels at the right ventricular wall (arrowheads). (b, c) Preoperative VR images (cardiac chambers removed with manual editing) clearly demonstrate the anomalous origin of the LCA (arrow in b, straight arrow in c) from the pulmonary trunk, along with multiple collateral vessels within the interventricular septum (arrowheads in b) and the dilated RCA (curved arrow in c). (d, e) Postoperative VR images, obtained after ligation of the original os of the LCA from the pulmonary trunk and creation of an anastomosis between the left internal mammary artery (short straight arrows) and the LCA (long straight arrow), demonstrate a decrease in the size of the RCA (curved arrow) and markedly diminished collateral vessels in the interventricular septum and right ventricular wall (*).
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Figure 9d. Bland-White-Garland syndrome in a 29-year-old woman. A = aorta, PA = pulmonary artery. (a) Preoperative anterior oblique VR image shows a dilated RCA (arrow) and the LAD artery with multiple collateral vessels at the right ventricular wall (arrowheads). (b, c) Preoperative VR images (cardiac chambers removed with manual editing) clearly demonstrate the anomalous origin of the LCA (arrow in b, straight arrow in c) from the pulmonary trunk, along with multiple collateral vessels within the interventricular septum (arrowheads in b) and the dilated RCA (curved arrow in c). (d, e) Postoperative VR images, obtained after ligation of the original os of the LCA from the pulmonary trunk and creation of an anastomosis between the left internal mammary artery (short straight arrows) and the LCA (long straight arrow), demonstrate a decrease in the size of the RCA (curved arrow) and markedly diminished collateral vessels in the interventricular septum and right ventricular wall (*).
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Figure 9e. Bland-White-Garland syndrome in a 29-year-old woman. A = aorta, PA = pulmonary artery. (a) Preoperative anterior oblique VR image shows a dilated RCA (arrow) and the LAD artery with multiple collateral vessels at the right ventricular wall (arrowheads). (b, c) Preoperative VR images (cardiac chambers removed with manual editing) clearly demonstrate the anomalous origin of the LCA (arrow in b, straight arrow in c) from the pulmonary trunk, along with multiple collateral vessels within the interventricular septum (arrowheads in b) and the dilated RCA (curved arrow in c). (d, e) Postoperative VR images, obtained after ligation of the original os of the LCA from the pulmonary trunk and creation of an anastomosis between the left internal mammary artery (short straight arrows) and the LCA (long straight arrow), demonstrate a decrease in the size of the RCA (curved arrow) and markedly diminished collateral vessels in the interventricular septum and right ventricular wall (*).
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Origin of the Coronary Artery or Branch from the Opposite or Noncoronary Sinus and an Anomalous Course.—
The four recognized patterns of an anomalous origin of a coronary artery from the opposite or noncoronary sinus are (a) the RCA arising from the left coronary sinus, (b) the LCA arising from the right coronary sinus, (c) the LCx or LAD artery arising from the right coronary sinus, and (d) the LCA or RCA (or a branch of either artery) arising from the noncoronary sinus. In these anomalies, the coronary ostium may be at the normal level, or the involved artery may have a high or low takeoff (13). Moreover, a coronary artery arising from the opposite or noncoronary sinus can take any of four common courses, depending on the anatomic relationship of the anomalous vessel to the aorta and the pulmonary trunk: (a) interarterial (ie, between the aorta and the pulmonary artery), (b) retroaortic, (c) prepulmonic, or (d) septal (subpulmonic) (Fig 10) (22). It is of great clinical importance which course is taken. Although retroaortic, prepulmonic, and septal (subpulmonic) courses seem to be benign, an interarterial course carries a high risk for sudden cardiac death (8,23,24).
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Figure 10. Drawings illustrate an LCA anomalously arising from the right coronary sinus (R) and four anomalous courses: interarterial (between the aorta and the pulmonary artery [PA]) (A), retroaortic (B), prepulmonic (C), and septal (subpulmonic [beneath the right ventricular outflow tract]) (D). L = left coronary sinus, N = noncoronary sinus.
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The RCA arises from the left sinus of Valsalva as a separate vessel or as a branch of a single coronary artery in 0.03%–0.17% of patients who undergo angiography (Fig 11) (25–27). The most common course of an anomalous RCA arising from the left sinus of Valsalva is interarterial (25); this variant can be associated with sudden cardiac death in up to 30% of patients (23). It has been postulated that, when dilation of the aorta occurs during exercise, the anomalous slit-like ostium for the RCA in the left sinus becomes narrower, possibly limiting coronary blood flow and resulting in myocardial infarction (9,28).
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Figure 11a. RCA arising from the left coronary sinus and taking an interarterial course in a 44-year-old man. (a) VR image of the top of the heart shows both the RCA (straight arrow) and the LCA (curved arrow) originating from the left coronary sinus. The RCA courses between the pulmonary artery (PA) and the aorta (A). Note the slit-like ostium (arrowhead) of the RCA. (b) Aortic root angiogram shows the anomalous origin of the RCA (arrow), but the exact location of the ostium is not identified.
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Figure 11b. RCA arising from the left coronary sinus and taking an interarterial course in a 44-year-old man. (a) VR image of the top of the heart shows both the RCA (straight arrow) and the LCA (curved arrow) originating from the left coronary sinus. The RCA courses between the pulmonary artery (PA) and the aorta (A). Note the slit-like ostium (arrowhead) of the RCA. (b) Aortic root angiogram shows the anomalous origin of the RCA (arrow), but the exact location of the ostium is not identified.
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The LCA arises from the right sinus of Valsalva as a separate vessel or as a branch of a single coronary artery in 0.09%–0.11% of patients who undergo angiography (Fig 12) (29). An interarterial course may be seen in up to 75% of patients with this anomaly (26,29), who are at high risk for sudden cardiac death due to the acute angle of the ostium, the stretch of the intramural segment, and the compression between the commissure of the right and left coronary cusps. However, this anomalous LCA may also take a retroaortic, prepulmonic, or septal (subpulmonic) course (30).
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Figure 12a. LCA arising from the right coronary sinus and taking a prepulmonic course in a 50-year-old man. (a) Axial oblique VR image shows the LCA (arrows) originating from the right coronary sinus and taking a prepulmonic course, passing anterior to the pulmonary artery (PA). A = aorta. (b) Oblique MIP image shows the separate origins of the LCA (arrows) and RCA (arrowhead) from the right coronary sinus, as well as the prepulmonic course of the LCA.
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Figure 12b. LCA arising from the right coronary sinus and taking a prepulmonic course in a 50-year-old man. (a) Axial oblique VR image shows the LCA (arrows) originating from the right coronary sinus and taking a prepulmonic course, passing anterior to the pulmonary artery (PA). A = aorta. (b) Oblique MIP image shows the separate origins of the LCA (arrows) and RCA (arrowhead) from the right coronary sinus, as well as the prepulmonic course of the LCA.
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Either the LCx artery or the LAD artery may anomalously arise from the right sinus of Valsalva (Figs 13, 14). The LCx artery is the artery that most commonly arises from a separate ostium within the right sinus or as a proximal branch of the RCA (approximately 0.32%–0.67% of the population) (30). Several reports have shown that this anomalous LCx artery passes behind the aortic root (25–27,31); fortunately, this anomaly has not been associated with death. The LAD artery may arise from the right sinus in tetralogy of Fallot, double outlet right ventricle, and transposition complexes, but rarely in patients with otherwise normal hearts. It may take either an interarterial or a prepulmonic course (13).
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Figure 13a. LCx artery arising from the right coronary sinus and taking a retroaortic course in a 45-year-old woman. VR image of the top of the heart (a) and coronary angiogram (b) show the LCx artery (straight arrow) originating from the right coronary sinus and passing behind the aorta (A). The RCA (curved arrow) demonstrates its normal origination from the right coronary sinus. PA = pulmonary artery.
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Figure 13b. LCx artery arising from the right coronary sinus and taking a retroaortic course in a 45-year-old woman. VR image of the top of the heart (a) and coronary angiogram (b) show the LCx artery (straight arrow) originating from the right coronary sinus and passing behind the aorta (A). The RCA (curved arrow) demonstrates its normal origination from the right coronary sinus. PA = pulmonary artery.
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Figure 14a. LAD artery arising from the right coronary sinus and taking a septal (subpulmonic) course in a 65-year-old man. (a) Coronal oblique VR image demonstrates both the LAD artery (long straight arrow) and the RCA (curved arrow) originating from the right coronary sinus. The LAD artery takes an intramuscular course beneath the right ventricular outflow tract (removed with manual editing). The LCx artery (short straight arrow) demonstrates its normal origination from the left coronary sinus. A = aorta. (b) Oblique MIP image reveals the unusual intramuscular course (arrowheads) of the proximal LAD artery, which emerges to the epicardial surface from the myocardium at the level of the middle portion of the artery. Arrow indicates the RCA. LV = left ventricle, PA = pulmonary artery. (c) Coronary angiogram shows a common origin for the LAD artery (straight arrow) and the RCA (curved arrow).
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Figure 14b. LAD artery arising from the right coronary sinus and taking a septal (subpulmonic) course in a 65-year-old man. (a) Coronal oblique VR image demonstrates both the LAD artery (long straight arrow) and the RCA (curved arrow) originating from the right coronary sinus. The LAD artery takes an intramuscular course beneath the right ventricular outflow tract (removed with manual editing). The LCx artery (short straight arrow) demonstrates its normal origination from the left coronary sinus. A = aorta. (b) Oblique MIP image reveals the unusual intramuscular course (arrowheads) of the proximal LAD artery, which emerges to the epicardial surface from the myocardium at the level of the middle portion of the artery. Arrow indicates the RCA. LV = left ventricle, PA = pulmonary artery. (c) Coronary angiogram shows a common origin for the LAD artery (straight arrow) and the RCA (curved arrow).
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Figure 14c. LAD artery arising from the right coronary sinus and taking a septal (subpulmonic) course in a 65-year-old man. (a) Coronal oblique VR image demonstrates both the LAD artery (long straight arrow) and the RCA (curved arrow) originating from the right coronary sinus. The LAD artery takes an intramuscular course beneath the right ventricular outflow tract (removed with manual editing). The LCx artery (short straight arrow) demonstrates its normal origination from the left coronary sinus. A = aorta. (b) Oblique MIP image reveals the unusual intramuscular course (arrowheads) of the proximal LAD artery, which emerges to the epicardial surface from the myocardium at the level of the middle portion of the artery. Arrow indicates the RCA. LV = left ventricle, PA = pulmonary artery. (c) Coronary angiogram shows a common origin for the LAD artery (straight arrow) and the RCA (curved arrow).
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Although either the RCA or the LCA may arise from the noncoronary sinus, both of these anomalies are rare in an otherwise normal heart (32,33) and usually have no clinical relevance. These anomalies may also be seen with transposition of the great arteries (13).
Anomalies of Course
Myocardial Bridging.—
Myocardial bridging is caused by a band of myocardial muscle overlying a segment of a coronary artery. It is most commonly localized in the middle segment of the LAD artery (34,35). There is some discrepancy between the prevalence of myocardial bridging at angiography (0.5%–2.5%) and that at pathologic analysis (15%–85%) (35). The cause for this discrepancy is presumed to be the fact that myocardial bridging often occurs without overt symptoms, so that patients are rarely referred for coronary angiography (36). In some cases, however, myocardial bridging is responsible for angina pectoris, myocardial infarction, life-threatening arrhythmias, or even death (34). The standard of reference for diagnosing myocardial bridges is coronary angiography, at which a typical "milking" effect and a "step down–step up" phenomenon induced by systolic compression of the tunneled segment may be seen (36). In contrast, multi–detector row CT clearly shows the intramyocardial location of the involved coronary arterial segment (Fig 15) (35). The ECG-gated reconstruction window used in standard multi–detector row CT of the coronary artery is usually positioned within the diastolic phase for maximal vasodilatation and minimal motion artifacts (37). However, when there is suspicion for myocardial bridging, it is recommended that ECG-gated reconstruction be performed during the systolic phase as well as the diastolic phase. Comparison of the images obtained during the two phases will allow assessment of luminal narrowing during the systolic phase (Fig 15).
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Figure 15a. Myocardial bridging in a 50-year-old man. (a, b) ECG-gated multi–detector row CT scans (short-axis two-chamber views) obtained during the diastolic (a) and systolic (b) phases show luminal narrowing of the intramyocardial segment of the LAD artery during the systolic phase (arrow). (c, d) Coronary angiograms obtained during the diastolic (c) and systolic (d) phases demonstrate the typical milking effect caused by systolic compression of the tunneled segment of the LAD artery (arrowheads).
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Figure 15b. Myocardial bridging in a 50-year-old man. (a, b) ECG-gated multi–detector row CT scans (short-axis two-chamber views) obtained during the diastolic (a) and systolic (b) phases show luminal narrowing of the intramyocardial segment of the LAD artery during the systolic phase (arrow). (c, d) Coronary angiograms obtained during the diastolic (c) and systolic (d) phases demonstrate the typical milking effect caused by systolic compression of the tunneled segment of the LAD artery (arrowheads).
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Figure 15c. Myocardial bridging in a 50-year-old man. (a, b) ECG-gated multi–detector row CT scans (short-axis two-chamber views) obtained during the diastolic (a) and systolic (b) phases show luminal narrowing of the intramyocardial segment of the LAD artery during the systolic phase (arrow). (c, d) Coronary angiograms obtained during the diastolic (c) and systolic (d) phases demonstrate the typical milking effect caused by systolic compression of the tunneled segment of the LAD artery (arrowheads).
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Figure 15d. Myocardial bridging in a 50-year-old man. (a, b) ECG-gated multi–detector row CT scans (short-axis two-chamber views) obtained during the diastolic (a) and systolic (b) phases show luminal narrowing of the intramyocardial segment of the LAD artery during the systolic phase (arrow). (c, d) Coronary angiograms obtained during the diastolic (c) and systolic (d) phases demonstrate the typical milking effect caused by systolic compression of the tunneled segment of the LAD artery (arrowheads).
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Duplication of Arteries.—
Duplication of the LAD artery in otherwise normal hearts has been reported to occur in 0.13%–1% of the general population (38). Duplication of the LAD artery consists of a short LAD artery, which courses and terminates in the anterior interventricular sulcus without reaching the apex, and a long LAD artery, which originates from either the LAD artery proper or the RCA, then enters the distal anterior interventricular sulcus and courses to the apex (Fig 16) (38). Because the LAD artery is the most important coronary artery in coronary artery bypass graft surgery, the radiologist should be aware of the possibility of duplication of the LAD artery manifesting at preoperative multi–detector row CT of the coronary artery so that he or she can forewarn the cardiac surgeon of the importance of achieving successful myocardial revascularization; otherwise, there is a risk of incorrect placement of the arteriotomy (39). Duplication of the LAD artery should not be confused with an LAD artery and a diagonal branch running parallel to each other. Such a parallel diagonal branch does not reenter the anterior interventricular sulcus and take over the course of the distal LAD artery, as does the long anterior LAD artery (40).
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Figure 16a. Duplication of the LAD artery in a 47-year-old man. (a) Anterior oblique VR image shows a dual LAD artery coursing along the anterior interventricular groove. Although the short LAD artery (short straight arrow) remains and terminates in the anterior interventricular groove, the long LAD artery (long straight arrow) reenters the groove from the anterior wall of the left ventricle. The diagonal branch (curved arrow) does not take this course. A = aorta, PA = pulmonary artery. (b) On a coronary angiogram, the origination of the septal branches (arrowheads) from the two arteries (arrows) proves that the arteries represent a dual LAD artery, not diagonal branches.
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Figure 16b. Duplication of the LAD artery in a 47-year-old man. (a) Anterior oblique VR image shows a dual LAD artery coursing along the anterior interventricular groove. Although the short LAD artery (short straight arrow) remains and terminates in the anterior interventricular groove, the long LAD artery (long straight arrow) reenters the groove from the anterior wall of the left ventricle. The diagonal branch (curved arrow) does not take this course. A = aorta, PA = pulmonary artery. (b) On a coronary angiogram, the origination of the septal branches (arrowheads) from the two arteries (arrows) proves that the arteries represent a dual LAD artery, not diagonal branches.
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Anomalies of Termination
Coronary Artery Fistula.—
Coronary artery fistula is a condition in which a communication exists between one or two coronary arteries and either a cardiac chamber, the coronary sinus, the superior vena cava, or the pulmonary artery (Fig 17). This condition is seen in approximately 0.1%–0.2% of all patients who undergo selective coronary angiography (41). It more commonly involves the RCA (60% of cases) than the LCA (40%) (42). In less than 5% of cases, fistulas originate from both the LCA and the RCA (7).
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Figure 17a. Coronary artery fistula in a 72-year-old woman. Oblique VR image (a) and coronary angiograms (b, c) show multiple tortuous communicating vessels (arrowheads) originating from the RCA (arrow in b) and the proximal LAD artery (arrow in c). The communicating vessels drain into the main pulmonary trunk. Enlargement of the proximal branches of the RCA and of the proximal LAD artery is also noted. A = aorta, PA = pulmonary artery.
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Figure 17b. Coronary artery fistula in a 72-year-old woman. Oblique VR image (a) and coronary angiograms (b, c) show multiple tortuous communicating vessels (arrowheads) originating from the RCA (arrow in b) and the proximal LAD artery (arrow in c). The communicating vessels drain into the main pulmonary trunk. Enlargement of the proximal branches of the RCA and of the proximal LAD artery is also noted. A = aorta, PA = pulmonary artery.
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Figure 17c. Coronary artery fistula in a 72-year-old woman. Oblique VR image (a) and coronary angiograms (b, c) show multiple tortuous communicating vessels (arrowheads) originating from the RCA (arrow in b) and the proximal LAD artery (arrow in c). The communicating vessels drain into the main pulmonary trunk. Enlargement of the proximal branches of the RCA and of the proximal LAD artery is also noted. A = aorta, PA = pulmonary artery.
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In coronary artery fistula, the involved coronary artery is dilated because of increased blood flow and is often tortuous to an extent determined by the shunt volume (8). In terms of morphologic features, the fistula is variable at its drainage site, with either single or multiple communications or a maze of fine vessels that form a diffuse network, or plexus, with extensive intramural distribution. The drainage site of the fistula has a greater clinical and physiologic importance than does the artery of origin. The most common site of drainage is the right ventricle (45% of cases), followed by the right atrium (25%) and the pulmonary artery (15%) (43). The fistula drains into the left atrium or left ventricle in less than 10% of cases (7). When the shunt leads into a right-sided cardiac chamber, the hemodynamics resemble those of an extracardiac left-to-right shunt; when the connection is to a left-sided cardiac chamber, the hemodynamics mimic those of aortic insufficiency. Myocardial perfusion may be diminished for that portion of the myocardium supplied by the abnormally connecting coronary artery. This situation represents a hemodynamic steal phenomenon and may lead to myocardial ischemia (44).
Coronary Arcade.—
Coronary arcade is a rare instance of communication that is large enough to be identified angiographically between the RCA and the LCA in the absence of coronary artery stenosis (45). Although the adult heart normally contains a profusion of small interconnecting vessels between the two coronary arteries, they are not usually seen at angiography. However, when these direct anastomoses are large enough to be identified angiographically, they can be differentiated from collateral vessels on the basis of the prominent straight connection between the two unobstructed major arteries, often at or near the level of the crux, in contrast to the tortuous collateral vessels between the patent vessel and the obstructed vessel (46).
Extracardiac Termination.—
Connections may exist between the coronary arteries and extracardiac vessels (ie, the bronchial, internal mammary, pericardial, anterior mediastinal, superior and inferior phrenic, and intercostal arteries and the esophageal branch of the aorta) (13). Moberg (47) demonstrated connections between the bronchial and coronary arteries in all patients, regardless of age and independent of the presence of atherosclerosis. These pathways become functionally significant only when a pressure gradient exists between the two arterial systems. This condition is generally associated with atherosclerotic coronary artery disease, which causes blood flow from the bronchial artery to the coronary arteries.
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Associated Congenital Heart Diseases
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Abstract
LEARNING OBJECTIVES FOR TEST...
