Nonatherosclerotic coronary findings and modifier E

In practice. It is identified on the curved reconstruction of the LAD and confirmed on cross-sectional views, where the tunneled segment is surrounded by myocardium. The findings name the vessel and segment and describe depth, length and, if both systolic and diastolic phases were acquired, systolic compression.

Pitfall. Reviewing only the tunnel and skipping the segment proximal to it. According to the review by Rovera 2023, plaque occurs mainly just proximal to the bridge and is uncommon within the tunnel.

Other sources. SCCT 2014 listed myocardial bridging among the potentially relevant anatomical variants, together with absent left main. Because of its high prevalence, some authors consider it a variant rather than a true anomaly, although most classifications count it among anomalies of course. The LAD is the most commonly affected artery, particularly its mid segment. (SCCT 2014, section 10.6.2, p. 352; Genoud 2026, sections 4.2 and 4.2.1 and Table 2; Rovera 2023, introduction)

In practice. The thickness of myocardium over the artery is measured on the cross-sectional view, and the tunnel length on the curved reconstruction. Systolic compression is assessed by comparing systole with diastole. According to SCCT 2026, bridge thickness and systolic and diastolic stenosis can independently predict symptoms, and diastolic stenosis has the highest diagnostic performance and predictive value for adverse outcomes.

Pitfall. Reporting a systolic compression percentage when only a diastolic phase was acquired. SCCT 2026 cautions that anatomical assessment is limited with a single phase.

Other sources. On invasive angiography, the Noble classification grades systolic compression of the LAD in three levels. Grade 1 is less than 50%, grade 2 is 50 to 75% and grade 3 exceeds 75%. On CCTA, SCCT 2026 divides systolic compression into absent, less than 50%, or 50% or more. (Noble 1976, cited by Xu 2022, methods; SCCT 2026, p. 12)

In practice. Each artery is followed from its ostium on axial images and oblique reconstructions of the aortic root. SCCT 2026 recommends describing origin, morphology, course, luminal caliber and termination, and the relationship to adjacent structures.

Pitfall. Reporting a conus branch that arises directly from the right sinus as anomalous. SCCT 2026 lists that origin as one of the two usual origins of the conus branch.

Other sources. SCCT 2021 uses ACAOS for origin from the opposite sinus of Valsalva. The ESC 2020 guideline uses AAOCA for anomalous aortic origin and ACAPA for origin from the pulmonary artery, with its ALCAPA and ARCAPA forms. In 2026, the International Coronary Artery Anomalies Collaborative (ICAAC), an international group of experts in coronary anomalies, used a Delphi method to propose a nomenclature for AAOCA. It is purely descriptive and does not assign risk. Its basic code combines the vessel, the sinus of origin and the proximal course, as in R-AAOCA/LS-IA. Other descriptors detail the ostium, the proximal course and a high origin. Because it covers only aortic origin, it does not include origin from the pulmonary artery. (SCCT 2021, section 4.10, p. 209; ESC 2020, section 4.17.1; Mery 2026, abstract; Tigges 2026, Radiopaedia, case rID 235236)

Source: Mery 2026, JACC Cardiovasc Imaging, abstract (scope and purpose of the nomenclature); Tigges 2026, Radiopaedia, case rID 235236 (meaning of each part of the code). The “On the map” column describes the current “Coronary artery origins” panel.

In practice. The proximal segment is followed on axial and oblique images until it reaches its groove. The interarterial course is considered high risk, and in systole the artery is compressed between the distended aorta and pulmonary artery. The transseptal course is compressed less, between the distended aorta and the contracted right ventricular outflow tract.

Pitfall. Naming the interarterial course without grading the narrowing of the proximal segment when it is present. SCCT 2026 asks for a description of luminal caliber, and CAD-RADS 2.0 assigns the category by the grade of that narrowing and adds E: with moderate stenosis, CAD-RADS 3/E.

Other sources. Some reviews describe five courses, adding the retrocardiac course, which passes behind the heart. Other names found in the literature are intraseptal for transseptal and precardiac for prepulmonic. This glossary follows the four courses of SCCT 2026. (Genoud 2026, section 4.1.3; Evangelista 2024; Karatoprak 2026, methods)

In practice. CT does not show it directly. It is inferred from an acute take-off angle, segmental narrowing with a slit-like orifice on the cross-sectional view, and incomplete encasement by pericoronary fat on the side facing the aortic lumen. When recognized, its length is measured.

Pitfall. Assessing the shape of the proximal lumen on the axial plane, which cuts the vessel obliquely. The slit-like orifice is seen on the cross-sectional view.

Other sources. In the Angelini classification, “intramural coronary artery” is another name for myocardial bridging. In this glossary, as in SCCT 2026, the intramural segment or course is the portion of the anomalous artery that runs within the aortic wall, and the tunneled segment of a bridge is called intramyocardial. SCCT 2026 also uses “intramural hematoma” in coronary dissection, where the hematoma lies within the wall of the coronary artery itself. (Ganga 2021, Table 1; Evangelista 2024; Genoud 2026, Figure 5; SCCT 2026, pp. 12–13)

In practice. Once the course is defined, the ostium and proximal segment are reviewed on cross-sectional views. The shape of the orifice, the take-off angle, the length of the narrowing and the height of the ostium relative to the sinotubular junction are reported.

Pitfall. Giving the same weight to an RCA from the left sinus as to a left coronary artery from the right sinus. ESC 2020 considers the latter more malignant.

Other sources. The ESC 2020 guideline considers an ostium located more than 1 cm above the sinotubular junction high risk. Other authors call any ostium above that junction a high origin, and SCCT 2026 does not set a distance. (ESC 2020, section 4.17.2 and note c; Karatoprak 2026, methods)

In practice. On axial and oblique images of the aortic root, review both sinuses until it is confirmed that one has no ostium, and follow each branch from the single ostium. Record the sinus, the type and, if a branch crosses the base of the heart, its course; in an interarterial branch, also look for an intramural segment, a slit-like orifice and proximal narrowing. To name the branches, SCCT 2026 defines each artery by the groove it runs in: the LAD, the anterior interventricular groove; the LCx, the left atrioventricular groove; and the RCA, the right atrioventricular groove (p. 4). CAD-RADS 2.0 includes anomalous coronary arteries among the causes of modifier E and notes that its list is not comprehensive. Narrowing of the interarterial branch is graded and carries E, as in its example of an interarterial anomaly with moderate stenosis (CAD-RADS 3/E).

Pitfall. Calling a single coronary artery benign without describing the course of the branches that cross the base of the heart. Elbadawi 2018 describes a benign course in types R-I and L-I, and Al Umairi 2019 associates a branch passing between the aorta and the pulmonary trunk with myocardial ischemia and sudden death.

Other sources. At catheterization, the reported frequency ranges from 0.024 to 0.066%. On CCTA, Al Umairi 2019 found 0.27% in 4,445 patients, more than the earlier series it cites (0.024 to 0.098%), and Katekaru-Tokeshi 2021 found 0.51% in a cardiovascular referral center, where 87.5% of the cases had other congenital heart disease. In complex congenital heart disease with abnormally positioned great arteries, Katekaru-Tokeshi 2021 considers the Leiden convention more applicable than the Lipton classification, which also does not include origin from the noncoronary sinus. (Al Umairi 2019, Introduction, Results and Discussion; Katekaru-Tokeshi 2021, abstract, Introduction and Results)

Source: Lipton 1979 and Yamanaka and Hobbs 1990, as reported by Al Umairi 2019 (Discussion) and Elbadawi 2018 (Table 1), because the originals could not be consulted; “Single coronary artery” tab verified on the map on 2026-10-09.

In practice. The maximum diameter is measured on the cross-sectional view and compared with the adjacent normal segment or with the largest coronary artery. In a saccular aneurysm the transverse diameter is greater than the longitudinal diameter; in a fusiform aneurysm the longitudinal diameter is greater.

Pitfall. Calling a dilation that involves more than half of the vessel an aneurysm. That diffuse dilation is ectasia, which SCCT 2026 attributes mainly to atherosclerosis.

In practice. Describe the affected vessels and segments, whether there are several separate areas of thickening (skip lesions), the grade of each stenosis and any aneurysms. Inflammation can extend from the aorta to the ostium and proximal segment of the coronary arteries, so the aortic wall is reviewed as well. In the acute phase, the double-ring sign may be seen: on the inside, the edematous, hypoattenuating intima; on the outside, the inflamed media and adventitia, with intense enhancement. CAD-RADS 2.0 does not give an example of vasculitis. Following its example of an anomaly with moderate stenosis (3/E), the narrowing is graded and E goes at the end of the code.

Pitfall. Reading smooth circumferential thickening as a concentric non-calcified plaque. Woodworth 2024 lists atherosclerosis among the mimics of vasculitis and suggests considering vasculitis when there is smooth, circumferential or continuous thickening, especially in acute coronary syndrome without traditional cardiovascular risk factors.

Other sources. SCCT 2026 lists Takayasu arteritis and giant cell arteritis, Kawasaki disease, ANCA-associated vasculitis, Behçet disease and HIV infection as causes. According to Gori 2021, ostial stenosis or occlusion predominates in Takayasu arteritis; aneurysms over stenoses in Kawasaki disease; and smooth, tapered, diffuse narrowing in giant cell arteritis, which rarely involves the coronary arteries. Gori includes IgG4-related disease, with periarteritis or aneurysms, which SCCT 2026 places under coronary encasement rather than vasculitis. (SCCT 2026, p. 13; Gori 2021, Biomedicines, Table 1 and section 5)

In practice. Describe the vessel and segment from which the feeding artery arises, its course, the drainage site and the number of feeding arteries and drainage sites, because, as Qureshi 2006 notes, there may be several feeding arteries or several drainage sites. Also report the caliber and tortuosity of the vessel, any aneurysm along its course with its maximal diameter, and complications visible on CT, such as thrombus within the fistula or chamber dilatation from volume overload. SCCT 2026 strongly recommends reporting anomalies by their origin, course and termination, as well as dilatation or aneurysm (Table 6). In CAD-RADS 2.0, fistula is one of the exceptions under modifier E. The category still depends on the stenosis and P on the plaque, E goes at the end of the code, and with no plaque or stenosis in any segment, the code is CAD-RADS 0/E.

Pitfall. Reporting a dilated, tortuous coronary artery as ectasia without following it to its termination, where the fistula that explains it may be found. SCCT 2026 describes the coronary arteries of a fistula in this way and counts fistula among the causes of compensatory ectasia.

Other sources. In the Gentile anatomical classification, reproduced by Genoud 2026, fistula is an anomaly of termination, congenital or acquired. Genoud 2026 calls it small if its caliber is smaller than that of the largest unaffected coronary artery, medium if it measures 1 to 2 times the diameter of the reference coronary artery, and large if it measures more than 2 times that diameter. A fistula larger than 8 mm is generally called giant. The described complications are coronary steal with ischemia, thrombosis, aneurysmal dilatation, heart failure, arrhythmias, endocarditis and rupture. In the CCTA series of Liu 2014, 60 of 66 patients had a coronary-pulmonary artery fistula, which drained into the left lateral aspect of the trunk in 54 of them. A jet of contrast into the lumen was seen in 46 of those 60, and in the other 14 only a small defect in the arterial wall. (Genoud 2026, Table 2 and sections 4.3 and 5.3; Qureshi 2006, section on clinical features; Liu 2014, results)

In practice. SCCT 2026 describes four forms of presentation, summarized in the table. Other findings may accompany them: epicardial fat stranding, beading, tortuosity, myocardial bridging, occlusion and absence of calcium. The myocardium of the territory may show perfusion defects and regional wall motion abnormalities. Vasospasm and coronary embolism can mimic it, and because of the spatial resolution of CCTA, a normal study does not exclude it. CAD-RADS 2.0 states that its categories are generally not used for nonatherosclerotic causes such as dissection, and it created modifier E for them, which goes at the end of the code. The narrowing is graded with the usual scale, and if no segment has plaque, P is not written. Applying the same rule as its 3/E example, a severe LAD stenosis is CAD-RADS 4A/E, and an occlusion is 5/E.

Pitfall. Calling smooth wall thickening without calcium “non-calcified plaque” in a young person with acute coronary syndrome. The SCCT 2023 terminology defines that plaque as atherosclerotic. According to SCCT 2026, intramural hematoma can be difficult to distinguish from it, and confirmation may require invasive angiography with intravascular imaging. Absence of calcium, abrupt or tapered stenosis, epicardial fat stranding and, according to the ESC, location in distal segments with otherwise normal or near-normal coronary arteries support dissection without confirming it. The opposite error also occurs: in the Tweet series, an apparent hematoma turned out to be non-calcified plaque on optical coherence tomography.

Other sources. The AHA and the ESC recommend invasive angiography as the first test when SCAD is suspected. The ESC gives the example of a young or middle-aged woman with few atherosclerotic risk factors, typical symptoms and positive biomarkers. According to the ESC, the sensitivity and specificity of CCTA for SCAD are unknown, and false negatives have been described. According to the AHA, CCTA often depicts dissection of distal segments, branches and vessels smaller than 2.5 mm poorly. Both see a possible role for it in follow-up. In the Tweet series, only two of the six CCTA reports issued before catheterization mentioned dissection in the differential diagnosis. (Hayes 2018 (AHA scientific statement), section on coronary CT angiography; Adlam 2018 (ESC position paper), sections on coronary CT angiography, associated angiographic findings and follow-up; Tweet 2019, results and discussion (Figure 7); SCCT 2023 terminology, Table 4)

Source: SCCT 2026, p. 13 (signs and definitions); Tweet 2019, abstract and results (per-patient frequencies; 14 patients and 16 vessels).

In practice. Table 3 of CAD-RADS 2.0 is not an exhaustive list. It includes dissection, anomalous origin, aneurysm or pseudoaneurysm, vasculitis, fistula, extrinsic compression, arteriovenous malformation and other causes. Nonatherosclerotic narrowing is graded, and an interarterial anomaly with moderate stenosis is CAD-RADS 3/E.

Pitfall. Adding P to the code of an anomaly when no segment has plaque. CAD-RADS 2.0 omits the P in its example of an interarterial anomaly without plaque.

Other sources. CAD-RADS 1.0 had only modifiers N, S, G and V, so a nonatherosclerotic finding had no code of its own. CAD-RADS 2.0 introduced modifiers I and E and renamed modifier V (vulnerable plaque) as HRP (high-risk plaque). (CAD-RADS 1.0, Table 1, p. 271; CAD-RADS 2.0, sections 3.3 and 3.3.6)