Anomalous Coronary Artery Angiography Made Simple

It’s a busy day in the cath lab. You and the rest of the lab are waiting for the case to move forward. The operator says to his assistant, “I’ve been looking for the right coronary for 10 minutes with 4 catheters. Where can it be?” The first thoughts that should come to mind are whether the artery is occluded at the aortic ostia or does it arise from another (anomalous) location? Avoiding the misdiagnosis of an unsuspected anomalous coronary artery is critical to the patient and it is always the angiographer’s responsibility to accurately define the origin and course of the vessel. One should not assume that a vessel is occluded because it is not visualized without a really good search and good clinical correlations.  Since even experienced angiographers have difficulty finding and delineating the true course of some anomalous vessels, a thorough method is required before making a definitive diagnosis. How should we approach the dilemma of finding an anomalous arising coronary artery? Let’s see if we can simplify the process.

Of course if we know there is an anomalous artery before coming to the cath from history or prior reports, we should recall that computed tomography angiography (CTA) is a better tool than angiography to confirm the diagnosis. CTA shows not only the artery and any obstructive disease, but also the true course of the vessel through the surrounding myocardial structures, differentiating the benign from the dangerous pathway (Figure 1).

The most common coronary anomalies

Of the dozens of coronary anomalies reported (Table 1), there are only about four that we may encounter over the course of a year. These include 1) the circumflex artery originating from the right coronary artery (RCA) or in the right coronary sinus; 2) RCA arising anteriorly in the non-coronary cusp or high above the coronary sinus (above the sino-tubular aortic ridge) on the aortic wall; 3) the left main artery originating from the right coronary sinus. This anomaly has 4 pathways, of which 1 is malignant and the other 3 are considered benign (see below); and 4) a separate origin of the left anterior descending and circumflex coronary arteries (often viewed as a very, very short left main artery).

“That’s a long left main artery…I wonder if there’s an anomalous circumflex?”

In the lab, I try to remind our fellows that when he or she sees a long left main coronary artery (LMCA) segment with a presumed small or trivial circumflex branch (sometimes thought to be occluded), that this particular image should trigger a cortical reflex and be accompanied by the following mantra, “Gee, that LM seems very long… I wonder if there is an anomalous circumflex?”) (Figure 2). The missing circumflex coronary artery will then be found arising from the right coronary cusp or the proximal RCA, and invariably follows a posterior path, moving behind and around the aortic root ultimately supplying the lateral wall of the left ventricle (LV). The retroaortic course can be easily seen in the right anterior oblique (RAO) projection as the circumflex moves leftward and behind the aorta.  

For all artery pathways that travel behind the aorta, the RAO projection during left ventriculography (Figure 3), aortography, or coronary angiography, will visualize the artery on end and appear as a radio-opaque “dot” posterior to the aorta. For the anomalous circumflex from the RCA, this is a benign variant of no clinical significance unless a significant stenosis is also present.  

The key observation for the anomalous circumflex is a “dot” behind the aorta seen in the RAO view.

Anomalous origin of the left main coronary artery (ALMCA)

When not seen coming from the left coronary sinus, the LM may originate from the right coronary sinus and will take 1 of 4 pathways to the LV (Figure 4): 1) the septal course, 2) the anterior course, 3) the retroaortic course, and 4) the interarterial course between aorta and pulmonary artery. Each course can be described in a simple method, coined by Serota H et al¹, the “dot and eye” method (Table 2). The 4 pathways of the ALMCA seen in the RAO projection are denoted by the 2 dots (either retroaortic or anterior, representing the interarterial course between great vessels), or an upward loop (or top of the eye) of the anterior course over the pulmonary artery, or lastly, a downward loop (or bottom of the eye) depicting the intraseptal course.

• The septal ALMCA runs an intramuscular course through the septum along the floor of the right ventricular (RV) outflow tract, traveling upward in the mid-septum, then branching into the LAD artery and left circumflex artery. Because the artery divides in the mid-septum, the LAD artery is relatively short and the initial portion of the circumflex artery courses toward the aorta. During RAO coronary angiography, the ALCMA and the circumflex coronary artery form an ellipse, with the LMCA forming the inferior portion and the circumflex artery forming the superior portion. Septal perforating arteries branching from the LMCA help identify this anomaly.
• The anterior ALMCA crosses the anterior free wall of the right ventricle over the pulmonary artery, then divides at the mid-septum into the LAD and circumflex arteries. During RAO coronary angiography, the ALMCA forms the superior portion of the “eye” and the circumflex forms the inferior portion.
• The retroaortic ALMCA passes posteriorly around the aortic root, ultimately landing on the anterior surface of the heart (Figure 5), dividing into the LAD and circumflex arteries of normal length and course. During RAO coronary angiography, the retroaortic ALMCA is seen “on end,” behind the aorta as a “dot” as seen with the CFX.
• The interarterial ALMCA courses between the aorta and pulmonary artery to its normal position on the anterior surface of the heart (Figure 6), dividing into the LAD and circumflex arteries of normal length and course. During RAO coronary angiography, the interarterial ALMCA is seen “on end,” anterior to the aorta as a “dot” in front of the aortic root.

Of the 4 pathways of the ALMCA, only this variant is considered dangerous, and is associated with exertional angina, syncope, and sudden death. The mechanism causing myocardial ischemia appears to be the slit-like opening in the aortic wall that narrows further during activity with the dynamic compression of the obliquely arising LMCA ostium. The theory that there is compression of the interarterial ALMCA between the aorta and pulmonary artery has not been proven. When this anomaly is identified, coronary revascularization or translocation is indicated in symptomatic patients. The need for revascularization in older patients with this anomaly is less clear. 

The key observation for the most important ALMCA is identifying the benign posterior or malignant anterior “dots” in the RAO view. Although suggested in the past, the placement of right-sided catheters or injection of contrast material into the pulmonary artery is unnecessary and often misleading.

Anomalous RCA (ARCA)

The anomalous origin of the RCA from the left coronary sinus or from the aorta above the coronary sinuses generally courses between the aorta and PA to its normal position. During RAO ventriculography (Figure 7), ARCA is seen “on end,” anterior to the aorta, and appears as a radio-opaque dot. This coronary anomaly has also been associated with symptoms of myocardial ischemia. When the ARCA arises from an anterior location or high above the sinus of Valsalva, an aortic root injection will help locate the ostium for sub selective catheter engagement using Amplatz left 2 or multipurpose catheters. 

Left coronary artery separate ostia

When the LAD and circumflex coronary arteries arise from separate ostia in the left coronary cusp, the normal proximal course of each is usually followed. Sub selective engagement of either the circumflex or the LAD with only one branch opacified may be confused with an occluded companion branch, if not well seen during the reflux of contrast. 

The bottom line

While most coronary angiography is straightforward, there will be times when the anomalous coronary artery defies selective cannulation. Perform aortography in several projections, search for the posterior or anterior ‘dots,’ and if all else fails, a CTA after the procedure to guarantee the complete understanding of the coronary circulation before making a final diagnosis may be needed.

References

1. Serota H, Barth CW, Seuc CA, Vandormael M, Aguirre F, Kern MJ. Rapid identification of the course of anomalous coronary arteries: the “dot and eye” method. Am J Cardiol. 1990;65:891-898.
2. Kern MJ. (Ed.) The Cardiac Catheterization Handbook, 5th Edition. Elsevier: Philadelphia, Pennsylvania; 2011: 1-456.
3. Kragel AH, Roberts WC. Anomalous origin of either the right or left main coronary artery from the aorta with subsequent coursing between aorta and pulmonary trunk: Analysis of 32 necropsy cases. Am J Cardiol. 1988 Oct; 62(10 Pt 1): 771-777.
4. Kadakia J, Gupta M, Budoff MJ. Anomalous “High Take-Off” of the right coronary artery evaluated by coronary CT angiography. Catheter Cardiovasc Interv. 2013 Nov; 82 (6): E765-E768.