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Keywords:

  • coronary artery anatomy;
  • coronary artery anomaly;
  • CT cardiac imaging;
  • CT coronary angiography;
  • dual source CT

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Normal coronary artery anatomy
  5. Coronary artery anomalies
  6. Conclusion
  7. References

Congenital abnormalities of the coronary arteries have an incidence of 1%, and most of these are benign. However, a small number are associated with myocardial ischaemia and sudden death. Various imaging modalities are available for coronary artery assessment. Recently, multi-detector CT has emerged as an accurate diagnostic tool for defining coronary artery anomalies. The purpose of this pictorial essay is to review the dual source CT appearance of congenital anomalies of the coronary arteries in adults.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Normal coronary artery anatomy
  5. Coronary artery anomalies
  6. Conclusion
  7. References

Congenital coronary anomalies are relative uncommon, having an incidence of approximately 1% of the population.[1, 2] Most anomalies are usually asymptomatic. However, some are haemodynamically significant and related to abnormalities of myocardial perfusion, which lead to an increased risk of myocardial ischaemia or sudden death. These anomalies include an anomalous origin of a coronary artery from the pulmonary artery, an anomalous course between the pulmonary trunk and the aortic root (inter-arterial) of the coronary artery arising from the opposite sinus of Valsalva, some types of myocardial bridging and large coronary artery fistula.[3] Recognition of coronary anomalies, particularly those associated with increased morbidity and sudden death, is important. Recently, multi-detector CT has been widely used to detect the coronary arteries anomalies as it provides excellent two-dimensional and three-dimensional visualisation of coronary arteries due to its high spatial and temporal resolution.

The aim of this pictorial essay is to review the normal anatomy of coronary artery system and illustrate the spectrum of congenital anomalies of the coronary arteries in adults as revealed by multi-detector CT. We searched our database for CT coronary artery examinations performed at our institution for suspected coronary artery disease and data of coronary artery anomalies were recorded. All examinations were performed in our institute on a dual source CT scanner (Somatom Definition, Siemens Medical Solutions, Forchheim, Germany).

Normal coronary artery anatomy[4, 5]

  1. Top of page
  2. Summary
  3. Introduction
  4. Normal coronary artery anatomy
  5. Coronary artery anomalies
  6. Conclusion
  7. References

The main coronary arteries are the right coronary artery (RCA) that arises from the right coronary sinus and the left main coronary artery (LM) that arises from the left coronary sinus and bifurcates into the left anterior descending artery (LAD) and left circumflex artery (CX) (Fig. 1a). The RCA is defined as an artery that runs in the right atrioventricular sulcus. Usually, the conal branch (CB) arises from the RCA. The LAD artery runs in the anterior interventricular groove and terminates near the apex of the heart. It provides diagonal branches to the anterior wall of the left ventricle. The CX artery runs in the left atrioventricular groove and gives off obtuse marginal branches to the lateral left ventricle (Fig. 1b). Occasionally, the LM trifurcates into the LAD, CX and the ramus intermedius (Fig. 2). In approximately 85% of individuals, the RCA gives rise to the posterior descending artery (PDA) and posterolaretal branches (PLB) (right dominance, Fig 3a). The circulation is left-dominant in 8% of individuals as the PDA arises from the CX artery (Fig 3b). In the remaining patients (7%), a co-dominant circulation system exists in which PDA originates from the RCA with PLB from the CX.

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Figure 1. Normal multi-detector CT anatomy of the coronary arteries. (a) Right-oblique volume-rendered (VR) image of the top of the heart shows the right coronary artery (RCA) and the left main coronary artery (LM) arise from the right coronary sinus and the left coronary sinus, respectively. (b) Left-oblique VR image of the top of the heart shows the LM and its branches.

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Figure 2. (a) Maximum intensity projection and (b) volume-rendered images show the left main coronary artery to trifurcates into the left anterior descending artery and left circumflex artery arteries and the ramus intermedius.

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Figure 3. (a) The distal right coronary artery divides into the PDA and posterior lateral branches in a right dominant anatomy. (b) In a left dominant anatomy, the left circumflex artery gives rise to the PDA.

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Coronary artery anomalies

  1. Top of page
  2. Summary
  3. Introduction
  4. Normal coronary artery anatomy
  5. Coronary artery anomalies
  6. Conclusion
  7. References

The coronary artery anomalies can be classified into anomalies of origin (number of coronary ostia, high take-off, ectopic coronary origin), anomalies of course (myocardial bridging) and coronary artery fistula.

Multiple ostia are considered as normal variants.[6] Typically, either the CB arises directly from the aorta (Fig. 4) or the LAD and CX arise separately with absence of the LM (Fig. 5). Single coronary ostium, in which only one coronary artery arises from the single ostium, is an extremely rare anomaly. This abnormality can have an adverse clinical outcome, particularly if one of the arteries crosses between the pulmonary artery and the aorta.[2]

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Figure 4. Maximum intensity projection (a) and volume-rendered (b) images show separate ostia of the right coronary artery and conal branch from the right coronary sinus.

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Figure 5. Multiple ostia with separate origins of the left anterior descending artery and left circumflex artery arteries. (a) Maximum intensity projection and (b) volume-rendered images.

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High take-off refers to the origin either of the RCA (Fig. 6) or the LM above the sinotubular junction, instead of being at the aortic sinus. This situation is usually without any haemodynamic significance and asymptomatic, but it may cause difficulties in cannulation of the vessel during coronary angiography.[3]

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Figure 6. High take-off of the right coronary artery (RCA). On maximum intensity projection (a) and oblique volume-rendered (b) images, the RCA demonstrates a high take-off above the sinotubular junction. Atherosclerotic change of the RCA with calcified plaque is also demonstrated.

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A coronary artery can arise from the non-coronary sinus or from the opposite sinus and then takes one of the four paths described later, depending on the anatomic relationship of the anomalous vessel to the aorta and the pulmonary trunk: inter-arterial (between the aortic root and the pulmonary trunk) (Fig. 7); retroaortic (dorsal to the aortic root) (Fig. 8); pre-pulmonic (anterior to the pulmonary artery or right ventricular outflow tract); transseptal or subpulmonic (beneath the right ventricular outflow track). The precise path taken by the artery is of great clinical importance. An inter-arterial course (previously called a malignant course) is associated with an increased risk of sudden cardiac death, while the other three courses are considered benign.[3, 6]

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Figure 7. Anomalous origin and course of the right coronary artery (RCA). (a) Maximum intensity projection and (b) volume-rendered images show the RCA arising from the left coronary sinus and taking an inter-arterial course.

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Figure 8. Anomalous origin and course of the left circumflex artery (CX). (a) Maximum intensity projection and (b) volume-rendered images display the CX originating from the right coronary artery and passing behind the aortic root.

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Either the RCA or the LM can arise from the pulmonary artery.[7, 8] In the most common form of this anomaly, the LM arises from the pulmonary trunk (anomalous left coronary artery from the pulmonary artery (ALCAPA) syndrome), and the RCA arises normally from the aorta. This condition is one of the most serious coronary artery anomalies, with a 90% mortality rate in the first year of life.[7] Most affected patients show symptoms in infancy and early childhood, while rarely, ALCAPA syndrome manifests in adults. To survive beyond infancy, patients with ALCAPA syndrome develop significant collateral circulation from the RCA to the LM. Computed tomography coronary angiography findings include direct visualisation of the LM arising from the main pulmonary artery (Fig. 9a,b), markedly dilated and tortuous coronary arteries (Fig. 9c,d) and collateral pathways between the RCA and the LM (Fig. 9e).

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Figure 9. CT coronary angiography findings of ALCAPA syndrome. (a) Maximum intensity projection (MIP) and (b) volume-rendered (VR) images clearly demonstrate the anomalous origin of the left main coronary artery from the pulmonary trunk. (c) MIP and (d) VR images show markedly dilated and tortuous coronary arteries. (e) MIP image shows multiple collateral vessels within the interventricular septum.

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Normally, the coronary arteries course in the epicardial fat. In myocardial bridge, a portion of the coronary artery courses through the myocardium. The band of myocardial muscle covering the artery is called a myocardial bridge, and the intramyocardial coronary artery itself is called a tunnelled segment.[9] Myocardial bridge is generally considered a benign condition that most commonly affects the middle segment of the LAD (Fig. 10). However, the relationship between this anomaly and increased cardiovascular morbidity is still unclear. According to previous reports,[9-11] myocardial bridge may caue coronary heart disease by two mechanisms: direct systolic compression of the tunnelled segment and enhanced atherosclerotic plaque formation occurring because of alteration of haemodynamic factors, mainly in the vessel segment proximal to bridge. The length, the depth (Fig. 11) and the location of myocardial bridge have been associated with the aforementioned mechanisms.[10, 11] Thus, these anatomical characteristics of myocardial bridge should be considered in the diagnosis. Computed tomography coronary angiography enables the depiction of myocardial bridge through direct visualisation of the tunnelled coronary segment and surrounding myocardium. In addition, the length and depth of tunnelled segment can be accurately determined. Additional indirect signs (such as systolic compression) can also be seen comparing the images obtained in both the end-systolic and end-diastolic phase.[9]

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Figure 10. Maximum intensity projection image (a) shows mid-left anterior descending artery segment courses through the ventricular myocardium (arrows). Cross-section image (b) shows tunnelled segment covered by a band of myocardial muscle (black arrow); note that the diagonal branches (white arrow) and the great cardiac vein (yellow arrow) course epicardially.

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Figure 11. Thirty-two-year-old man with deep myocardial bridging, which is associated with chest pain. (a) Maximum intensity projection image shows the course of the proximal left anterior descending artery dipping into the myocardium. (b) Volume-rendered image provides an excellent demonstration of myocardial bridge (arrows).

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Coronary artery fistula is an anomalous termination of the coronary arteries leading to an abnormal communication between a coronary artery and either a great vessel (Fig. 12) or a cardiac chamber.[12] The vast majority (more than 90%) of the fistulas drain into the venous circulation creating a left to right shunt. Clinical symptoms are based on the induced haemodynamic abnormality. Patients with small coronary artery fistulas remain asymptomatic, whereas those with high-flow fistulas may develop haemodynamic steal phenomenon with consequent myocardial ischaemia.[2, 13]

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Figure 12. Coronary–pulmonary artery fistula. (a) Maximum intensity projection MIP and (b) volume-rendered images show a plexus of fine tortuous vessels arising from the dilated conal branch and draining into pulmonary artery. (c, d) MIP images demonstrate a flow jet to the pulmonary artery through the fistula.

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Conclusion

  1. Top of page
  2. Summary
  3. Introduction
  4. Normal coronary artery anatomy
  5. Coronary artery anomalies
  6. Conclusion
  7. References

Multi-detector CT coronary angiography is a non-invasive technique that depicts coronary artery anomalies with high accuracy providing important information for accurate diagnosis and planning patient management.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Normal coronary artery anatomy
  5. Coronary artery anomalies
  6. Conclusion
  7. References
  • 1
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  • 2
    Zeina AR, Blinder J, Sharif D, Rosenschein U, Barmeir E. Congenital coronary artery anomalies in adults:non-invasive assessment with multidetector CT. Br J Radiol 2009; 82: 254261.
  • 3
    Kim SY, Seo JB, Do KH et al. Coronary artery anomalies: classification and ECG-gated multi-detector row CT findings with angiographic correlation. Radiographics 2006; 26: 317333.
  • 4
    Pannu HK, Flohr TG, Corl FM, Fishman EK. Current concepts in multi-detector row CT evaluation of the coronary arteries: principles, techniques, and anatomy. Radiographics 2003; 23: 111125.
  • 5
    Patel S. Normal and anomalous anatomy of the coronary arteries. Semin Roentgenol 2008; 43: 100112.
  • 6
    Young PM, Gerber TC, Williamson EE, Julsrud PR, Herfkens RJ. Cardiac imaging: part 2, normal, variant, and anomalous configurations of the coronary vasculature. AJR Am J Roentgenol 2011; 197: 816826.
  • 7
    Pena E, Nguyen ET, Merchant N, Dennie G. ALCAPA syndrome: not just a pediatric disease. Radiographics 2009; 29: 553565.
  • 8
    Williams IA, Gersony WM, Hellenbrand WE. Anomalous right coronary artery arising from the pulmonary artery: a report of 7 cases and a review of the literature. Am Heart J 2006; 152: 1004; e9–17.
  • 9
    Leschka S, Koepfli P, Husmann L et al. Myocardial bridging: depiction rate and morphology at CT coronary angiography––comparison with conventional coronary angiography. Radiology 2008; 246: 754762.
  • 10
    Nakanishi R, Rajani R, Ishikawa Y, Ishii T, Berman DS. Myocardial bridging on coronary CTA: an innocent bystander or a culprit in myocardial infarction? J Cardiovasc Comput Tomogr 2012; 6: 313.
  • 11
    Ishikawa Y, Kawawa Y, Kohda E et al. Significance of the anatomical properties of a myocardial bridge in coronary heart disease. Circ J 2011; 75: 15591566.
  • 12
    Tomasian A, Lell M, Currier J, Rahman J, Krishnam MS. Coronary artery to pulmonary artery fistulae with multiple aneurysms: radiological features on dual-source 64-slice CT angiography. Br J Radiol 2008; 81: 218220.
  • 13
    Zenooz NA, Habibi R, Mammen L, Finn JP, Gilkeson RC. Coronary artery fistulas: CT findings. Radiographics 2009; 29: 781789.