What are the findings of anatomic anomalies on coronary computed tomography angiography (CCTA)?

Updated: Dec 21, 2017
  • Author: Eugene C Lin, MD; Chief Editor: Eugene C Lin, MD  more...
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Coronary artery anomalies can be broadly classified as anomalies of origin, anomalies of course, and anomalies of termination. [75]

In anomalous cases, the coronary arteries should be identified by their location rather than by their origin or specific branches. The right coronary artery lies in the right atrioventricular groove and supplies the right ventricular free wall. The LAD lies in the anterior interventricular groove and supplies the anterior interventricular septum (the LAD need not give rise to diagonal branches). The left circumflex artery lies in the left atrioventricular groove and supplies the left ventricular free wall.

Most anomalies are incidental findings but may be important during surgical planning to avoid accidental vascular injury. Only a few anomalies are potentially malignant, with the potential to result in ischemia, infarction, or sudden death. These include origin of the artery from the opposite coronary sinus with interarterial course, pulmonary artery origin, and coronary artery fistulae. Patients with anomalous coronary artery origin from the pulmonary arteries show symptoms in infancy and early childhood.

The left and right coronary arteries can arise from the noncoronary sinus or the opposite sinus. In these cases, the arteries can take 4 courses: retroaortic, prepulmonic, septal (beneath the right ventricular outflow tract), or interarterial (between the aorta and pulmonary artery). Patients with an interarterial course, particularly of the left coronary artery, are at risk for ischemia, infarction, and sudden cardiac death, particularly during exercise. (See the images below.)

Anomalous right coronary artery (RCA): Axial CT im Anomalous right coronary artery (RCA): Axial CT image of an anomalous RCA arising from the left coronary sinus, with an interarterial course between the aorta and pulmonary artery.
Anomalous left circumflex: Axial CT image of an an Anomalous left circumflex: Axial CT image of an anomalous circumflex artery (arrow) passing posterior to the aorta.

Myocardial bridging, [76] also called tunneled artery, is a congenital anomaly where myocardium encases a segment of coronary artery. It is most common in the mid-LAD. The artery may be compressed in the systolic phase. Although it is usually a benign anomaly, it has been associated with myocardial ischemia. Myocardial bridging is well demonstrated by CCTA. As most diagnostic images are obtained in diastole, it is important to also review systolic images, if available, to evaluate for systolic compression. Atherosclerotic changes are more common proximal to the tunneled artery. (See the image below.)

Myocardial bridging: Maximum intensity projection Myocardial bridging: Maximum intensity projection (MIP) image demonstrates a myocardial bridge (arrow) involving the mid-left anterior descending artery (LAD).

Myocardial loops refer to muscle bundles from the atrial myocardium surrounding three quarters of the circumference of an artery. These are of no clinical significance.

Coronary artery fistulas are usually congenital and can be symptomatic if large. They are well visualized by CCTA. Coronary artery fistulas originate from the RCA in two thirds of cases and the left coronary system in a quarter of cases. More than 90% drain into the right atrium, coronary sinus, or right ventricle. [77] On CCTA, contrast opacification of the receiving chamber/vessel (shunt sign) [77] is useful for determining the exact site of entry of the fistula. However, this finding will be obscured if there is a significant amount of preexisting contrast in the receiving chamber/vessel. (See the image below.)

Coronary artery fistula: Volume-rendered CT image Coronary artery fistula: Volume-rendered CT image (A) demonstrates a fistula from the left anterior descending (LAD) artery (arrow) to the right ventricular outflow tract (RVOT) (arrowhead). Coronal CT image (B) demonstrates a small jet of contrast in the region of the shunt entrance (arrow) into the RVOT.

Other anomalies are not hemodynamically significant but important to describe in detail if intervention is a possibility. For example, a dual LAD can result in diagnostic error during cardiac catheterization or in technical difficulty during revascularization.

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