Normal and Variant Coronary Arterial and Venous Anatomy on High-Resolution CT Angiography

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1 CT ngiography of Coronary rterial and Venous natomy Cardiac Imaging Pictorial Essay Sunil Kini 1, 2 Kostaki G. is 2 Leroy Weaver 2, 3 Kini S, is KG, Weaver L Keywords: anatomy, anomalies, arteriography, cardiac imaging, coronary arteries, CT angiography, heart, MDCT DOI: /JR Received September 30, 2006; accepted after revision January 15, Present address: Quantum Medical Radiology, tlanta, G Department of Diagnostic Radiology, William eaumont Hospital, 3601 W 13 Mile Rd., Royal Oak, MI ddress correspondence to K. G. is (kbis@beaumont.edu). 3 Present address: Elkhart General Healthcare System, Elkhart, IN CME This article is available for CME credit. See for more information. JR 2007; 188: X/07/ merican Roentgen Ray Society Normal and Variant Coronary rterial and Venous natomy on High-Resolution CT ngiography OJECTIVE. This article displays the normal and variant anatomy of the coronary arteries and subjacent cardiac veins using a high-resolution 64-MDCT scanner. CONCLUSION. Knowledge of the anatomy of the coronary arteries and subjacent cardiac veins as displayed with maximum intensity and volume-rendered projections is important for correct image interpretation of coronary CT angiography examinations. ontrast-enhanced CT angiography C (CT) of the coronary arteries is becoming feasible as temporal and spatial resolution improves with the availability of MDCT. Detection, characterization, and quantification of coronary artery disease and elegant delineation of coronary anatomy are possible using 2D multiplanar reformation (MPR), 3D maximum-intensity-projection (MIP), and 3D volume-rendered postprocessing techniques. Familiarity with coronary artery and venous anatomy and anatomic variants is important for correct image interpretation. This anatomy and the arterial variants have been well described using conventional angiographic techniques [1, 2]. However, the cross-sectional nature of CT has the benefit of more precisely displaying the spatial relationships of coronary arterial and venous anatomy with respect to cardiac structures. This article highlights this anatomy with a variety of MIP and volume-rendered techniques (Figs. 1 18). Subjects and Methods Coronary CT protocols usually image the heart using cranial-to-caudal acquisition [3]. However, caudal-to-cranial scanning acquisitions are implemented when concomitant imaging of the pulmonary arteries is desired in patients with atypical chest pain [4]. We describe both of these protocols because the cardiac venous anatomy may be displayed with variation in enhancement depending on the type of data acquisition. The patients who participated in our study were imaged after the institutional review board had approved the study, which complies with the Health Insurance Portability and ccountability ct, and after they had provided written informed consent. Patients were recruited from October 2004 to June Imaging was performed on a 64-slice (32-detector) MDCT scanner (Sensation Cardiac 64, Siemens Medical Solutions) after the patient was premedicated with oral atenolol ( mg), IV metoprolol (5- to 10-mg boluses, up to 50 mg), or both. n upper extremity 20-gauge IV catheter was used for venous access. Sublingual nitroglycerin (0.4 mg) was provided to induce coronary vasodilatation. olus timing was measured in the mid ascending aorta with 20 ml of iodixanol (320 mgi/ml [Visipaque, GE Healthcare]) administered at a rate of 5 ml/s followed by a 50-mL saline flush, also administered at a rate of 5 ml/s). lternatively, bolus tracking can be used to trigger data acquisition by placing a region of interest over the mid ascending aorta and setting the trigger threshold to 160 H above baseline. Single-sector reconstructions of the coronary arteries were performed at 65% and 35% of the R-R length and were then modified to a different phase start if there were motion artifacts. Reconstructions were performed on a workstation (Wizard, Siemens Medical Solutions) and then transferred to another workstation (TeraRecon, TeraRecon) for MPRs and MIPs. Cases were selected to show the normal coronary arterial and venous anatomy. MIPs were obtained using various thicknesses (5 30 mm) and were displayed using standard orientations (right anterior oblique, left anterior oblique, axial) with or without caudal or cranial angulation. Volume-rendered images were also obtained using various orientations. Cranial-to-Caudal cquisition Coronary CT was performed 5 seconds after aortic peak density; 100 ml of iodixanol (Visipaque) was administered at 5 ml/s and was fol- JR:188, June

2 lowed by a 50-mL saline flush at 5 ml/s [3]. Retrospective ECG-gating was used with the following parameters: collimation, 0.6 mm; tube rotation time, 0.33 seconds; tube voltage, 120 mv; effective ms, ; pitch, 0.2; and scanning time, seconds. Scanning coverage was from the level of the carina to the bottom of the heart. Reconstruction field of view, slice thickness and reconstruction increment, and smooth kernel were as follows: cm; 0.6 and 0.3 mm, respectively; and 25f. ECG pulsing is usually implemented for tube current modulation and is needed to reduce radiation exposure [5]. Caudal-to-Cranial cquisition For the caudal-to-cranial acquisition, a patient preparation and scanning protocol similar to that described in the previous section was used. However, contrast injection was performed with a higher volume of contrast material using a biphasic protocol: 100 ml of iodixanol was administered at 5 ml/s followed by 30 ml of iodixanol at 3.0 ml/s and then a 50-mL saline flush at 3 ml/s. The additional volume of contrast material resulted in a prolonged time for contrast injection to ensure adequate enhancement of the pulmonary arteries [4]. s a result, streak artifacts arising from the superior vena cava and right atrium were present in 37 (88%) of 42 studies; however, these artifacts interfered with the visualization of the right coronary artery (RC) in only one (2.4%) of the 42 cases [4]. The thorax from the lung bases to just above (1 2 cm) the aortic arch was scanned with a 12- to 15-second acquisition (no ECG pulsing), but scanning can include the entire thorax when ECG pulsing is applied. s with cranial-to-caudal acquisitions, ECG pulsing is needed to reduce radiation exposure [5]. Reconstruction field of view, slice thickness and reconstruction increment, and kernel for the coronary arteries were similar to those for the cranial-to-caudal acquisition. However, reconstructions were also obtained with a larger field of view [4] to display the pulmonary arteries, thoracic aorta, lungs, and thoracic soft tissues. Normal natomy of the Coronary rteries The right and left coronary arteries originate from the right and left sinuses of Valsalva of the aortic root, respectively. The posterior sinus rarely gives rise to a coronary artery and is referred to as the noncoronary sinus. The locations of the sinuses are anatomic misnomers: The right sinus is actually anterior in location and the left sinus is posterior. The myocardial distribution of the coronary arteries is somewhat variable, but the right coronary artery (RC) almost always supplies the right ventricle (RV), and the left coronary artery (LC) supplies the anterior portion of the ventricular septum and anterior wall of the left ventricle (LV). The vessels that supply the remainder of the LV vary depending on the coronary dominance, which we explain later. RC natomy The RC arises from the right coronary sinus somewhat inferior to the origin of the LC. fter its origin from the aorta, the RC passes to the right of and posterior to the pulmonary artery and then emerges from under the right atrial appendage to travel in the anterior (right) atrioventricular (V) groove (Figs. 1 and 2). In about half of the cases, the conus branch is the first branch of the RC (Fig. 3). In the other half, the conus branch has an origin that is separate from the aorta. The conus branch always courses anteriorly to supply the pulmonary outflow tract. Occasionally, the conus branch can be a branch of the LC (Fig. 3D), have a common origin with the RC, or have dual or multiple branches. In 55% of cases, the sinoatrial nodal artery (Figs. 3C, 3D, and 4) is the next branch of the RC, arising within a few millimeters of the RC origin. In the remaining 45% of cases, the sinoatrial nodal artery arises from the proximal left circumflex (LCx) artery (Figs. 4 and 11). In either case, the sinoatrial nodal artery always courses toward the superior vena cava inflow near the cephalad aspect of the interatrial septum. s the RC travels within the anterior V groove, it courses downward toward the posterior (inferior) interventricular septum. s it does this, the RC gives off branches that supply the RV myocardium; these branches are called RV marginals or acute marginals (Fig. 5). They supply the RV anterior wall. fter it gives off the RV marginals, the RC continues around the perimeter of the right heart in the anterior V groove and courses toward the diaphragmatic aspect of the heart. Coronary Dominance The artery that supplies the posterior descending artery (PD) and the posterolateral branch determines the coronary dominance. If the PD and PL arise from the RC, then the system is said to be right dominant (80 85% of cases) (Figs. 6 and 7). In this instance, the RC supplies the inferoseptal and inferior segments of the LV [6]. If the PD and PL arise from the LCx artery, then the system is said to be left dominant (15 20% of cases) (Figs. 8 and 17). In this instance, the LC supplies the inferoseptal and inferior segments of the LV. If the PD comes from the RC and the PL comes from the LCx artery, the system is codominant (about 5% of cases) (Fig. 9). In left-dominant and codominant systems, the LCx artery continues in the posterior V groove as the left V groove artery and gives rise to left PL. In left dominance, the PD is the final branch of the V groove artery. The distal RC divides into the PD and PL in a right-dominant system. The nondominant system is usually noticeably smaller in caliber than the dominant system. This difference in caliber can be used as an additional clue to determine whether the coronary anatomy is right or left dominant. Usually arising just distal to the origin of the PD, the V nodal artery (Fig. 6) can be recognized by its direct vertical course off of the distal RC. In cases of left dominance, the V node branch has a similar appearance and location, but it arises just proximal to the (left) PD. LC natomy The LC normally emerges from the left coronary sinus as the left main (LM) coronary artery (Fig. 10). The LM coronary artery is short (5 10 mm), passes to the left of and posterior to the pulmonary trunk, and bifurcates into the left anterior descending (LD) and LCx arteries (Fig. 11). Occasionally, the LM coronary artery trifurcates into the LD artery, the LCx artery, and the ramus intermedius artery (Fig. 12). Ramus Intermedius rtery The most common variation in LC anatomy is the presence of a trifurcation of the LM coronary artery. In this instance, the LM coronary artery trifurcates into the LD artery, LCx arteries, and an artery between them called the ramus intermedius artery (Fig. 12). The ramus intermedius artery itself has variable branching. The ramus intermedius can be distributed as a diagonal branch or as an obtuse marginal branch depending on whether it supplies the anterior or the lateral wall, respectively. LD rtery The LD artery (Fig. 13) runs in the anterior interventricular sulcus along the ventricular septum. Commonly, the LD artery may be embedded within the anterior myocardium forming an overlying myocardial bridge (Fig. 14). Myocardial bridging is seen more often on CT than described in the coronary angiography literature. Most myocardial bridges are asymptomatic, although rarely myocardial 1666 JR:188, June 2007

3 CT ngiography of Coronary rterial and Venous natomy bridging can be associated with ischemia. The LD artery has branches called septal perforators (Fig. 14) that supply the anterior ventricular septum. It also has diagonal arteries (Fig. 15) that course over and supply the anterior wall of the LV. The diagonals and septal perforators are numbered sequentially from proximal to distal (i.e., D1, D2, S1, S2). LCx rtery The LCx artery (Figs. 16, 17, and 2, 4, 8, 11, 12, 15) runs in the posterior V groove analogous to the course of the RC on the opposite side. The major branches of the LCx artery consist of obtuse marginals (OMs) (Figs. 16 and 17). OM branches supply the lateral wall of the LV. They are numbered sequentially from proximal to distal (i.e., OM1, OM2, OM3). nomalies of RC Origin The RC can have an anomalous origin. It is important to be aware of this possibility to avoid misinterpreting coronary CT. Typically, the anomalous origin of the RC is from the left coronary sinus of Valsalva, with a subsequent course between the aortic root and right ventricular outflow tract. Depiction of these anomalies is beyond the scope of this article; however, this and other anomalies of RC origin are described by Kim et al. [7]. n example of an anomalous origin of the RC is shown in Figure 18. nomalies of LC Origin The LC and its branches can have an anomalous origin. It is important to be aware of this possibility to avoid misinterpreting coronary CT. Some of these anomalies are associated with an increased risk of sudden death or cardiac arrest (Fig. 18C). Depiction of these anomalies is beyond the scope of this article; however, anomalies of LM, LD, and LCx origin are reviewed by Kim et al. [7]. Coronary Venous natomy The great cardiac vein (Figs. 4 and 16) is located in the anterior interventricular sulcus, alongside the LD artery. It courses upward from the apex and drains into the coronary sinus. The middle cardiac vein (Figs. 7 and 7C) also begins at the apex, but it courses upward in the inferior interventricular sulcus, alongside the PD. etween the two, there is a variable posterolateral vein (Fig. 7C) draining the lateral wall of the LV. The coronary sinus (Figs. 7, 7C, 16, and 16) is the wide vein that courses in the posterior V groove accompanying the LCx artery and the V groove artery. It drains into the right atrium and receives the great cardiac vein proximally and the middle cardiac vein distally. Reporting System of Coronary rtery Disease In an attempt to standardize the reporting of coronary artery disease, an ad hoc committee of the merican Heart ssociation developed nomenclature and further divided the main coronary arteries into proximal, middle, and distal segments [8]. The proximal RC segment is from the ostium to one half the distance to the acute margin of the heart. The middle RC segment is the RC from the end of the above segment to the acute margin of heart. The distal RC segment is the RC running along the right V groove from the acute margin to the origin of the PD. The LD proximal segment is proximal to and includes the origin of the first major septal perforator. The middle LD segment is the LD artery immediately distal to the origin of the first major septal perforator that extends to the point where the LD artery forms an angle (right anterior oblique view). This angle is often, but not always, close to the origin of the second diagonal. If this angle or diagonal is not identifiable, this segment ends one half the distance from the first major septal perforator to the apex. The apical LD segment is the terminal portion of the LD artery that begins at the end of the previous segment and extends to or beyond the apex. The proximal LCx segment is the mainstem of the LCx artery from its origin off the LC to and including the origin of an obtuse marginal. The distal LCx segment is the LCx artery distal to the origin of the obtuse marginal and travels along or close to the posterior V groove. Conclusion Coronary CT is emerging as an essential imaging tool for evaluating the coronary arteries. Knowledge of the CT appearance of the coronary anatomy and various coronary artery anomalies is essential for accurate diagnosis and proper patient treatment. References 1. Green CE. Coronary cinematography. Philadelphia, P: Lippincott-Raven, Soto, Russell RO, Moraski RE. Radiography anatomy of the coronary arteries: an atlas. Mount Kisco, NY: Fitura Publishing, Raff GL, Gallagher MJ, O Neil WW, Goldstein J. Diagnostic accuracy of noninvasive coronary angiography using 64-slice computed tomography. J m Coll Cardiol 2005; 46: Vrachliotis TG, is KG, Hardary, et al. Enhancement of coronary, aortic and pulmonary vasculature using biphasic single-injection 64-slice CT: angiography protocol in emergency department patients with atypical chest pain. Radiology (forthcoming, May 2007) 5. Jakobs TF, ecker CR, Ohnesorge, et al. Multislice helical CT of the heart with retrospective ECG gating: reduction of radiation exposure by ECG-controlled tube current modulation. Eur Radiol 2002; 12: Cerqueira MD, Weisman NJ, Dilsizian V, et al. Standardized myocardial segmentation and nomenclature for tomographic imaging of the heart. statement for healthcare professionals from the Cardiac Imaging Committee of the Council on Clinical Cardiology of the merican Heart ssociation. Circulation 2002; 105: Kim SY, Seo J, Do KH, et al. Coronary artery anomalies: classification and ECG-gated multi-detector row CT findings with angiographic correlation. RadioGraphics 2006; 26: usten WG, Edwards JE, Frye RL, et al. reporting system on patients evaluated for coronary artery disease: Report of the d Hoc Committee for Grading of Coronary rtery Disease, Council on Cardiovascular Surgery, merican Heart ssociation. Circulation 1975; 51[suppl 4]:5 40 JR:188, June

4 Fig. 1 nterior schematic diagram of heart shows course of dominant right coronary artery and its tributaries. V = atrioventricular, PD = posterior descending artery, RC = right coronary artery, RV = right ventricular, S = sinoatrial. C D Fig. 2 CT images of normal heart in 53-year-old man. o = aortic root, CS = coronary sinus, L = left atrium, LD = left anterior descending artery, LCx = left circumflex artery, LM = left main coronary artery, LV = left ventricle, PD = posterior descending artery, R = right atrium, RC = right coronary artery, RV = right ventricle, RVOT = right ventricular outflow tract., xial 5-mm maximum-intensity-projection (MIP) image shows left main coronary artery as it arises from left coronary cusp., xial 5-mm MIP image shows right coronary artery as it arises from right coronary cusp inferior to level of beginning of left main coronary artery. C, xial 5-mm MIP image shows course of right coronary artery within anterior atrioventricular groove. Left anterior descending artery is shown within anterior interventricular groove, and left circumflex artery is shown in posterior atrioventricular groove. D, xial 5-mm MIP image shows origin of posterior descending artery from distal right coronary artery JR:188, June 2007

5 CT ngiography of Coronary rterial and Venous natomy C D Fig. 3 Conus branch anatomy variations. o = aortic root, L = left atrium, LD = left anterior descending artery, LM = left main coronary artery, LV = left ventricle, R = right atrium, RC = right coronary artery, RVOT = right ventricular outflow tract, SN = sinoatrial node branch., Left anterior oblique 5-mm maximum-intensityprojection (MIP) image shows conus branch (arrow) in 44-year-old woman as it arises separate from right coronary artery off of right coronary cusp., Left anterior oblique 15-mm MIP image shows common origin of conus branch (arrow) and right coronary artery in 40-year-old man. C, xial 10-mm MIP image shows conus branch (arrow) arising from proximal RC in 52-year-old man. It then courses anteriorly toward right ventricular outflow tract. D, xial 10-mm MIP image shows conus branch (arrow) arising from left anterior descending artery in 46-year-old man. Fig. 4 Sinoatrial node branch variations. o = aortic root, D1 = first diagonal, GCV = great cardiac vein, L = left atrium, LD = left anterior descending artery, LCx = left circumflex artery, LM = left main coronary artery, OM1 = first obtuse marginal, RC = right coronary artery, RVOT = right ventricular outflow tract, SVC = superior vena cava., xial 10-mm maximum-intensity-projection (MIP) image in 64-year-old man shows large sinoatrial node branch (arrow) as it arises from proximal right coronary artery. It then courses posteriorly toward cephalad aspect of interatrial septum (arrowheads) posterior to inflow of superior vena cava., xial 10-mm MIP image shows sinoatrial node branch (arrow) in 65-year-old woman as it arises from proximal left circumflex artery: Sinoatrial branch still courses toward cephalad aspect of interatrial septum. JR:188, June

6 Fig. 5 Marginal branch anatomy. F = foot, LD = left anterior descending artery, LV = left ventricle, RC = right coronary artery, RV = right ventricle., Right anterior oblique 10-mm maximum-intensity-projection (MIP) image shows large marginal branch (arrow) arising from right coronary artery (RC) in 40-year-old woman., Right anterior oblique volume-rendered image shows marginal branch (arrow) of RC as it courses over right ventricle in 45-year-old woman. Fig. 6 Distal right coronary artery anatomy in 34-yearold man. Left anterior oblique 20-mm maximumintensity-projection image shows course of entire right coronary artery. Distally, posterior descending artery and posterior lateral branch are shown, as is atrioventricular node branch. o = aortic root, VN = atrioventricular node, IM = inferior marginal branch, LCx = left circumflex artery, LV = left ventricle, PD = posterior descending artery, PL = posterior lateral branch, RC = right coronary artery, RVOT = right ventricular outflow tract. C Fig. 7 Distal dominant right coronary artery variation on axial projections. CS = coronary sinus, LV = left ventricle, MCV = middle cardiac vein, PD = posterior descending artery, PL = posterior lateral branch, PLV = posterolateral vein, R = right atrium, RC = right coronary artery, RV = right ventricle., xial 10-mm maximum-intensity-projection (MIP) image in 51-year-old man shows typical tortuous course of posterior descending artery as it arises from distal right coronary artery. Posterior descending artery travels in inferior interventricular groove along side middle cardiac vein. Posterior lateral branch continues along distal coronary sinus to supply inferior wall., xial 10-mm MIP image shows dual posterior descending arteries and dual posterior lateral branches in 44-year-old man. C, xial 3D volume-rendered projection image shows origin of posterior descending artery, which still courses toward middle cardiac vein, is higher than normal in 49-yearold woman JR:188, June 2007

7 CT ngiography of Coronary rterial and Venous natomy C Fig. 8 Dominant left circumflex artery and posterior descending artery anatomy. o = aortic root, VG = atrioventricular groove artery, CS = coronary sinus, L = left atrium, OM = obtuse marginal, PD = posterior descending artery, PL = posterior lateral branch, R = right atrium, RC = right coronary artery. and, Left anterior oblique 10-mm maximum-intensity-projection (MIP) images show two examples of dominant left circumflex artery anatomy with typical small nature of right coronary artery: one in 43-year-old woman () and one in 44-year-old man (). trioventricular groove artery descends as larger-caliber artery in posterior atrioventricular groove subjacent to coronary sinus. C, xial 10-mm MIP image shows dual posterior descending arteries as they arise from distal atrioventricular groove artery in 44-year-old man with dominant left circumflex artery. Fig. 9 Codominance. xial 10-mm maximumintensity-projection image reveals codominant anatomy in which posterior descending artery arises from right coronary artery and posterior lateral branch arises from distal left circumflex artery in 33-year-old man. LV = left ventricle, PD = posterior descending artery, PL = posterior lateral branch, RC = right coronary artery, RV = right ventricle. Fig. 10 Dominant left coronary artery anatomy. Left anterior oblique schematic diagram of dominant left coronary artery anatomy, including left anterior descending artery and left circumflex artery tributaries, is shown. VG = atrioventricular groove artery, PD = posterior descending artery. JR:188, June

8 Fig. 11 Left main coronary artery bifurcation. nterior caudal 10-mm maximum-intensity-projection image displays typical bifurcation of left main coronary artery into left anterior descending and left circumflex arteries in 47-year-old man. VG = atrioventricular groove artery, D1 = first diagonal, LD = left anterior descending artery, LCx = left circumflex artery, LM = left main coronary artery, OM1 = first obtuse marginal, SN = sinoatrial node branch. C Fig. 12 Ramus intermedius anatomy. LD = left anterior descending artery, LCx = left circumflex artery, LM = left main coronary artery, RI = ramus intermedius artery., Right anterior oblique caudal 10-mm maximum-intensity-projection (MIP) image displays trifurcation of left main coronary artery into left anterior descending artery, ramus intermedius artery, and left circumflex artery in 49-year-old man., xial 10-mm MIP image shows left main coronary artery dividing into left anterior descending artery, left circumflex artery, and ramus intermedius branches in 42-yearold woman. C, Left posterior cranial 3D volume-rendered projection image shows branching ramus intermedius artery, which is mostly distributed as obtuse marginal branch to lateral wall, in 52-year-old man. Fig. 13 Left anterior descending artery course. Right anterior oblique 10-mm maximum-intensity-projection image reveals entire course of left anterior descending artery within anterior interventricular groove in 44- year-old woman. Distally, it is seen wrapping around left ventricular apex (arrows). L = left atrium, LV = left ventricle JR:188, June 2007

9 CT ngiography of Coronary rterial and Venous natomy Fig. 14 Myocardial bridge and septal perforator branch anatomy in 39-year-old woman. L = left atrium, L = left atrial appendage, LV = left ventricle, S1, S2, S3 = first, second, and third septal perforators., Right anterior oblique 10-mm maximum-intensityprojection (MIP) image displays left anterior descending artery and septal perforator branches. Myocardial bridge overlies left anterior descending artery just beyond second septal perforator (arrows)., Short-axis (left anterior oblique) 5-mm MIP image at level of myocardial bridge shows left anterior descending artery (arrow) deep to right ventricular myocardium junction with left ventricle. Fig. 15 Diagonal branch anatomy. D1 = first diagonal, D2 = second diagonal, LD = left anterior descending artery, LCx = left circumflex artery, LM = left main coronary artery, LV = left ventricle, RI = ramus intermedius artery, SP = septal perforator branches., xial caudal oblique 10-mm maximum-intensityprojection (MIP) image reveals two diagonal branches (D1 and D2) from left anterior descending artery in 55- year-old man. Diagonal branches course laterally, and small septal perforator branches course medially., Cranial left anterior oblique 10-mm MIP image shows left anterior descending artery and two diagonal branches in 47-year-old man. Fig. 16 Nondominant left circumflex artery anatomy in 36-year-old man. VG = atrioventricular groove artery, CS = coronary sinus, D1 = first diagonal, GCV = great cardiac vein, LD = left anterior descending artery, LCx = left circumflex artery, OM1 = first obtuse marginal., xial 10-mm maximum-intensity-projection (MIP) image shows left circumflex artery and left anterior descending artery with large first obtuse marginal arising from proximal left circumflex artery. Small left circumflex artery descends in posterior atrioventricular groove as atrioventricular groove artery., Left anterior oblique 10-mm MIP image displays left circumflex artery anatomy with its descent as atrioventricular groove artery. JR:188, June

10 Fig. 17 Dominant left circumflex artery anatomy in 44-year-old man. VG = atrioventricular groove artery, LCx = left circumflex artery, LM = left main coronary artery, OM1 = first obtuse marginal, OM2 = second obtuse marginal, PD = posterior descending artery, PL = posterior lateral branch, RI = ramus intermedius artery., Left anterior oblique cranial 3D volume-rendered image shows dominant left circumflex artery anatomy with two obtuse marginal branches., xial 3D volume-rendered image reveals dual posterior descending artery and posterior lateral branch arising from distal atrioventricular groove artery. C Fig. 18 nomalous origin of right coronary artery and left main coronary artery. o = aortic root, LD = left anterior descending artery, LM = left main coronary artery, RC = right coronary artery, RVOT = right ventricular outflow tract., xial 5-mm maximum-intensity-projection (MIP) image shows anomalous origin of right coronary artery in 43-year-old woman from anterior proximal ascending aorta with subsequent acute rightward course before reaching anterior atrioventricular groove., Three-dimensional volume-rendered projection image shows anomalous right coronary artery in same patient as above level of right coronary cusp (arrow). C, xial 10-mm MIP image reveals anomalous origin of left main coronary artery in 35-year-old man from right cusp near origin of right coronary artery. It then takes intraseptal course posterior to right ventricular outflow tract near cephalad aspect of interventricular septum. FOR YOUR INFORMTION This article is available for CME credit. See for more information JR:188, June 2007