The grammar
Stenosis / plaque burden / modifiers
CAD-RADS is a patient-level communication system for coronary atherosclerotic disease on CTCA. It does not replace the vessel-by-vessel findings; it compresses them into a standard summary linked to clinical context.
Example: CAD-RADS 3/P2/HRP/I− means a moderate maximal stenosis, moderate overall plaque burden, high-risk plaque morphology, and a performed CT ischaemia test that is negative for lesion-specific ischaemia.
First complete anatomy, segmental plaque/stenosis, quality, stents/grafts, and functional analysis. The code is the final summary—not a shortcut around the study.
The first field
Patient category follows the worst atherosclerotic stenosis
| Category | Maximal diameter stenosis | Meaning |
|---|---|---|
| CAD-RADS 0 | 0%; no plaque | No coronary atherosclerosis on CTCA. |
| CAD-RADS 1 | 1–24%, or plaque without visible narrowing | Minimal nonobstructive CAD. |
| CAD-RADS 2 | 25–49% | Mild nonobstructive CAD. |
| CAD-RADS 3 | 50–69% | Moderate stenosis. |
| CAD-RADS 4A | 70–99% in one or two vessels | Severe stenosis. |
| CAD-RADS 4B | Left main ≥50% or three-vessel ≥70% disease | High-risk severe anatomical pattern. |
| CAD-RADS 5 | 100% | Total/subtotal occlusion. |
| CAD-RADS N | Significant disease cannot be excluded | Non-diagnostic study/segment under the N rules. |
Apply the scale to vessels/branches ≥1.5 mm when image quality is sufficient. The category is based on atherosclerotic stenosis; non-atherosclerotic narrowing belongs under modifier E and descriptive reporting.
The high-grade fork
4A, 4B, and 5 are not interchangeable
- 4A: one or two vessels with 70–99% stenosis. A severe proximal LAD lesion is 4A unless the 4B definition is met.
- 4B: left main ≥50%, or obstructive three-vessel disease with ≥70% in all three major epicardial territories.
- 5: a total/subtotal occlusion, whether acute or chronic; describe chronicity clues and viability/territory separately.
Count major vessels, not every branch as an independent “vessel.” A 70–99% lesion in LAD plus another in D1 is not automatically two-vessel disease. The body of the report must show the anatomy behind the patient-level category.
The second field
P1–P4: grade the entire coronary plaque burden
| P grade | Burden | CAC | SIS | Visual guide |
|---|---|---|---|---|
| P1 | Mild | 1–100 | ≤2 | 1–2 vessels with mild plaque. |
| P2 | Moderate | 101–300 | 3–4 | 1–2 vessels with moderate plaque, or 3 with mild plaque. |
| P3 | Severe | 301–999 | 5–7 | 3 vessels with moderate plaque, or 1 with severe plaque. |
| P4 | Extensive | >1000 | ≥8 | 2–3 vessels with severe plaque. |
No P0 is required. CAD-RADS 0 already means no plaque and no stenosis. In CAD-RADS 1–5, append the selected P grade after the stenosis category: for example, CAD-RADS 2/P3.
CAC, SIS, visual assessment, or validated quantitative plaque volume may be used according to local practice. State or internally standardise the method so follow-up and audits are meaningful.
When tools disagree
CAC counts calcium; CTCA sees total plaque
The P methods need not give the same category. A patient with CAC 20 but diffuse noncalcified plaque can have mild calcified burden yet substantial total CTCA plaque. Conversely, a densely calcified limited segment can produce a high CAC with fewer involved segments.
- Use total quantitative plaque burden when technically valid and available.
- Otherwise integrate CTCA visual burden/SIS rather than allowing CAC to erase noncalcified plaque.
- Document the method and choose the grade that best represents overall plaque according to institutional policy.
- Do not average incompatible grades into a fictitious number.
The optional fields
Use modifiers for defined facts—not decoration
| Modifier | Meaning | Trigger |
|---|---|---|
| N | Non-diagnostic | At least one clinically relevant segment >1.5 mm cannot be confidently interpreted. |
| S | Stent | At least one coronary stent is present. |
| G | Graft | At least one coronary bypass graft is present. |
| HRP | High-risk plaque | At least two HRP features within a plaque. |
| I | CT ischaemia assessment | CT-FFR or stress CT perfusion performed: I+, I−, or I±. |
| E | Exception | Clinically important non-atherosclerotic coronary abnormality. |
Recommended syntax is stenosis, then P grade, then modifiers separated by slashes. Keep the impression readable: the code never replaces explanatory prose.
The most tested rule
N is a category or a modifier depending on what is already proven
| Evaluable segments | Non-evaluable segment(s) | Correct form |
|---|---|---|
| No stenosis, minimal, or mild only (<50%) | Could hide ≥50% disease | CAD-RADS N/Px if burden can be assessed; N replaces the numeric stenosis category. |
| At least one proven ≥50% stenosis | Additional segment non-evaluable | CAD-RADS 3–5/Px/N; retain the known numeric category and append N. |
Example: mild LCx plaque plus motion-obscured proximal RCA = CAD-RADS N/P1, not CAD-RADS 2/N. But moderate LAD stenosis plus motion-obscured RCA = CAD-RADS 3/P2/N.
State the exact non-diagnostic segment and cause. “Limited study” is insufficient because downstream action depends on the territory and whether obstructive disease remains possible.
Prior revascularisation
S and G identify the altered coronary map
Stent modifier S
Use S when any coronary stent is present. Grade in-stent restenosis using the same stenosis bands when the lumen is evaluable. If the stent is non-evaluable and no other ≥50% stenosis is seen, use N/Px/S.
Graft modifier G
Use G when bypass grafts are present. Evaluate origin, body, distal anastomosis, runoff, and native vessels. A severe native lesion successfully bypassed by a fully patent graft is not used to inflate the CAD-RADS category; a graft occlusion is CAD-RADS 5/Px/G.
In CABG, the clinically relevant circulation includes grafts, anastomoses, native targets, competitive flow, and ungrafted territories. A numeric category without the graft map is unsafe.
Morphology modifier
HRP requires at least two features in the same plaque
The four features are positive remodelling, low attenuation (<30 HU focus with careful technique), napkin-ring sign, and spotty calcification. Append HRP only when at least two are present.
- One feature: describe it in the body; do not use HRP.
- HRP can accompany nonobstructive disease—for example, CAD-RADS 2/P2/HRP.
- HRP increases concern but does not independently prove culprit status or ischaemia.
- Do not call a plaque “vulnerable” as a promise of future rupture; CAD-RADS 2.0 uses “high-risk plaque.”
Functional modifier
I+, I−, and I± require a CT ischaemia test
| Modifier | CT-FFR | Stress CT perfusion |
|---|---|---|
| I+ | Lesion-specific value ≤0.75 in a vessel suitable for PCI, interpreted with the pressure curve. | Reversible defect or peri-infarct ischaemia. |
| I− | Lesion-specific value >0.80. | No reversible ischaemia; a fixed infarct alone is I− and should be described. |
| I± | 0.76–0.80, requiring location, symptoms, ΔCT-FFR, and context. | Borderline/equivocal perfusion result. |
Do not assign I from a resting first-pass hypoperfusion impression on routine CTCA. Modifier I specifically indicates CT-FFR or stress myocardial CT perfusion analysis.
Outside atherosclerosis
E flags non-atherosclerotic coronary abnormalities
Examples include dissection, anomalous origin/course, aneurysm/pseudoaneurysm, vasculitis, fistula, extrinsic compression, and arteriovenous malformation. E indicates that the atherosclerotic stenosis code does not capture the whole problem.
Example: no atherosclerotic plaque, but an anomalous RCA with interarterial/intramural course: CAD-RADS 0/E, followed by a complete anomaly description. The E modifier is not a substitute for that description or for urgent communication when required.
Same code, different context
Stable and acute chest pain tables guide different actions
The stenosis and P categories are the same, but clinical recommendations differ. In acute chest pain, troponin, ECG, haemodynamic state, culprit morphology, and alternative diagnoses determine urgency. CAD-RADS is not an ACS rule by itself.
- CAD-RADS 0 in an appropriate acute-pain CT pathway can support exclusion of coronary atherosclerotic cause, but still assess noncoronary emergencies and clinical data.
- Nonobstructive plaque with HRP may be important in an acute syndrome even without ≥50% narrowing.
- CAD-RADS 4B/5 or a suspected culprit requires timely specialist communication—not merely a code in a routine report.
Codes inform; patients decide
Keep recommendations contextual
CAD-RADS tables provide management considerations, but the final recommendation must reflect the indication, symptoms, acute versus stable setting, comorbidities, anatomy, physiology, local resources, and clinician–patient decision-making.
- 0: consider non-atherosclerotic causes of symptoms.
- 1–2: preventive risk-factor assessment; no routine functional test solely for mild stenosis.
- 3: consider functional assessment if it will change management; optimise prevention/anti-anginal care.
- 4A: functional assessment or invasive angiography depending on location, symptoms, and context.
- 4B: invasive evaluation is generally recommended.
- 5: invasive/functional/viability assessment according to acute/chronic presentation and territory.
- N: alternative/additional evaluation may be needed because obstructive disease is not excluded.
Final assembly
A seven-step CAD-RADS workflow
- Confirm indication and acute/stable context.
- Finish segmental interpretation; list non-evaluable segments.
- Assign the worst atherosclerotic stenosis category.
- Determine P1–P4 from the institution’s chosen whole-tree burden method.
- Apply N logic before other modifiers.
- Add S, G, HRP, I result, and E only when their definitions are met.
- Write a plain-language impression and actionable recommendation beside the code.
Order: CAD-RADS [stenosis or N]/P[1–4]/[modifiers]. Avoid undocumented custom abbreviations.
Code it yourself
Worked CAD-RADS cases
Case A · Plaque without narrowing; SIS 1
CAD-RADS 1/P1. Visible plaque excludes category 0 even when the lumen is normal.
Case B · Maximum 40% stenosis; diffuse plaque in six segments
CAD-RADS 2/P3. Mild worst stenosis and severe total burden are deliberately allowed to diverge.
Case C · 60% LAD; calcium-obscured RCA
CAD-RADS 3/Px/N. A proven ≥50% lesion preserves numeric category; N flags the additional uncertainty.
Case D · Mild evaluable disease; proximal RCA non-diagnostic
CAD-RADS N/Px. N replaces category 1/2 because significant RCA disease cannot be excluded.
Case E · 80% LAD in-stent restenosis; P3
CAD-RADS 4A/P3/S. Grade the evaluable stent lumen like native stenosis and append S.
Case F · Patent LIMA–LAD bypasses occluded proximal LAD; mild RCA/LCx
CAD-RADS 2/Px/G if graft/anastomosis/runoff are patent. The successfully bypassed native LAD occlusion does not set the category.
Case G · 55% lesion; CT-FFR 0.73 distal; two HRP features
CAD-RADS 3/Px/HRP/I+. State lesion location, CT-FFR sampling position, and symptoms/context in prose.
Case H · No plaque; coronary fistula
CAD-RADS 0/E. Then describe donor, course, drainage, aneurysm, and shunt effects completely.
Common errors
What breaks the system
- Calling plaque-free arteries CAD-RADS 1 instead of 0—or visible plaque CAD-RADS 0.
- Using the P grade as if it were the stenosis grade.
- Assigning HRP for one feature.
- Adding I without CT-FFR or stress CT perfusion.
- Using CAD-RADS 4B for any two severe lesions or any left-main plaque.
- Writing CAD-RADS 2/N when N should replace the number.
- Letting a bypassed native occlusion inflate an otherwise patent graft circulation.
- Reporting only the code and omitting vessel-level disease, artifacts, and recommendation.
Active recall
Self-test: answer before opening
1. What are the three CAD-RADS 2.0 fields?
Worst stenosis category, whole-tree plaque burden P1–P4, then applicable modifiers.
2. What distinguishes 4A from 4B?
4A is 70–99% in one or two vessels; 4B is left main ≥50% or three-vessel obstructive disease with ≥70% stenosis.
3. What are P1–P4 CAC ranges?
P1 1–100; P2 101–300; P3 301–999; P4 >1000.
4. What are P1–P4 SIS ranges?
P1 ≤2; P2 3–4; P3 5–7; P4 ≥8 involved segments.
5. When does N replace the numeric category?
When at least one important segment is non-diagnostic and evaluable segments show no stenosis ≥50%, so obstructive disease cannot be excluded.
6. When is N appended to a number?
When a ≥50% stenosis is already proven in an evaluable segment but another important segment remains non-diagnostic.
7. What does the HRP modifier require?
At least two high-risk plaque features within a plaque.
8. What CT-FFR ranges define I+, I±, and I−?
I+ ≤0.75; I± 0.76–0.80; I− >0.80, using a lesion-specific value and full context.
9. How is a severe native lesion treated if a patent graft bypasses it?
It does not set the CAD-RADS category when the graft, anastomosis, and runoff are fully patent; grade the clinically functioning grafted circulation and append G.
10. What belongs under E?
Clinically important non-atherosclerotic coronary abnormalities such as anomaly, dissection, aneurysm, vasculitis, fistula, or extrinsic compression.
Printable quick revision
One-page CAD-RADS 2.0 card
- 0: no plaque/no stenosis. 1: 1–24 or plaque/no narrowing. 2: 25–49. 3: 50–69.
- 4A: 70–99% in 1–2 vessels. 4B: LM ≥50 or 3-vessel ≥70. 5: occlusion.
- P by CAC: 1–100 · 101–300 · 301–999 · >1000.
- P by SIS: ≤2 · 3–4 · 5–7 · ≥8.
- N: no known ≥50 → N/Px; known ≥50 → numeric/Px/N.
- HRP: ≥2 features. I: only after CT-FFR or stress CTP.
- S/G: presence of stent/graft; still describe patency and restenosis.
- E: anomaly/dissection/aneurysm/fistula/other non-atherosclerotic disease.
- Final rule: code + plain-language vessel findings + clinical recommendation.
Provenance
Sources and scope
This chapter follows Dr Zeeshan Lakhani’s Webinar 4 CAD-RADS 2.0 teaching. Automated captions contain transcription errors; the coding rules and thresholds were checked against the multisociety consensus and 2026 SCCT interpretation update.
- CAD-RADS 2.0 multisociety expert consensus — definitive categories, P grades, modifiers, and management tables.
- CAD-RADS 2.0 open consensus version — N logic, plaque methods, I thresholds, and worked examples.
- SCCT Interpretation and Reporting of CCTA: 2026 Update — current integration of CAD-RADS 2.0 into structured CCTA reporting.
Educational material only. Management tables require clinical context and local pathways; urgent findings require direct communication. CAD-RADS is a summary of a complete CTCA interpretation, not a standalone diagnosis. External references require internet; this chapter works offline.
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