The recent report by Opolski et al on the prevalence and characteristics of coronary artery anomalies (CAAs) is an important contribution to expanding our base of knowledge on the subject. I would like to discuss a few critical points the report raises.

Names can be catchy and simple, but the nuances of their use can be confusing, especially to unsophisticated audiences. Historically, the use of the phrase “anomalous coronary artery from the opposite sinus” (frequently used as a synonym for ACAOS) has been an attempt to identify with a single acronym a uniform anatomic entity that has a wide spectrum of manifestations but that is consistently attributable to myocardial ischemia, which worsens the patient’s prognosis. The abbreviation may be misleading, because it is often used to identify “all anomalies with origin of a coronary artery from the opposite sinus of Valsalva” but also, more precisely and differently, all cases of “anomalous aortic origin of a coronary artery with an intramural obstructive proximal course.” In fact, the consensus is that CAAs should not be considered consistent, uniformly pathologic clinical entities, because only a few of them can cause symptoms of myocardial ischemia (chest pain, dyspnea, dizziness, syncope, sudden cardiac arrest, and death). Eckart et al best clarified this point; they concluded that anomalous origin of the left coronary artery from the right sinus of Valsalva with intramural course was the only type of CAA that caused sudden death in military recruits during 2 months of strenuous exercise at boot camp (33% of all nontraumatic sudden deaths).

After the introduction of intravascular ultrasonography, in vivo imaging of CAAs allowed even more precise studies, leading to the conclusion that where the anomalies originated mattered less than their proximal coronary courses in causing ischemic symptoms. Currently, mapping out the intramural course of the artery (inside the aortic media) seems to be the best way to determine the severity and type of CAA. This is why it has recently been proposed that “ACAOS” be used to refer only to the anatomic varieties of anomalies that feature intramural compression within the aortic wall. Unfortunately, current computed tomographic angiographic technology, although useful for other purposes, has not been able to clearly identify an “intramural course,” mainly because the software programs in clinical use today eliminate the aortic wall and primarily show the luminal tomographic anatomy. However, in dedicated projections, computed tomographic angiography can reveal the approximate severity of the cross-sectional area (see Figure 3 in Opolski et al’s report), as recently discussed. By considering information gained from computed tomographic angiography and the accurate course of anomalous CAA, we can generically diagnose this anomaly (strictly defined to imply an intramural course), because now we know that all cases with a similar course, at the sinotubular junction, have intramural compression to some degree.

In their study, Opolski et al did not use this definition, resulting in 2 major limitations. First, many of their patients with ACAOS (≥32 of 72 [44%]) were not expected to feature any ischemic mechanism (such as the left coronary artery from the right sinus of Valsalva with an intraseptal course, or origin of the circumflex from the right sinus with a retroaortic course). Second, although the investigators succeeded in presenting amazingly precise coronary images, as in their Figure 3, they should be willing to recognize that these are tomographic images 0.6 mm in thickness (probably obtained during systole), but the real stenosis has a phasic behavior, and is more complex. In fact, intravascular ultrasonography shows that the cross-sectional area changes dramatically during the systolic and diastolic cycle. Lateral compression and hypoplasia of the cross-sectional area at the intramural course are the mechanisms of stenosis. The conclusion seems to be that only intravascular ultrasonography can currently help subclassify a given case of ACAOS by its severity of stenosis.