The Coronary Artery Disease Reporting and Data System (CAD-RADS) was created to provide a standardized reporting system for coronary CT angiography. Its primary goal is to improve communication between the ordering provider and the reading clinician — and to provide specific recommendations that guide further patient management.
The CAD-RADS classification is assigned based entirely on the highest-grade lesion detected on the scan.
1 Stenosis categories
A few categories have important sub-rules:
Subdivided by extent:
4A: 70–99% stenosis in a single vessel or two vessels.
4B: > 50% stenosis in the left main, or 3-vessel obstructive disease (≥ 70% in three vessels).
100% stenosis. Subdivided into subtotal vs chronic total occlusion (CTO). A CTO is generally defined by > 3 months of symptoms or a lesion > 10 mm in length on CTA.
The N classification has two distinct uses depending on what else is on the scan:
As an overall category (CAD-RADS N) — when the highest-grade stenosis is non-obstructive (< 50%) but at least one segment is non-evaluable, the report is downgraded to N because obstructive disease can’t be safely excluded.
As a modifier (e.g. CAD-RADS 4/N) — when there’s a known obstructive stenosis (≥ 50%, i.e. categories 3, 4, or 5) alongside a non-evaluable segment, the N is simply appended.
2 Modifiers
Categories are frequently complemented by modifiers. When more than one is present, separate them with a / (e.g. CAD-RADS 4/S/G/V).
Indicates the presence of a stent anywhere in the coronary system.
Indicates the presence of a surgical bypass graft.
Apply when the plaque exhibits at least two high-risk features:
- Positive remodeling
- Low attenuation / low-density necrotic core (< 30 HU)
- Spotty calcification
- Napkin-ring sign — central dark low-attenuation plaque with a brighter peripheral rim
See the dual-use rule above — either upgrades to an overall N (when stenosis is non-obstructive) or appends as a modifier (when obstructive disease is already present).
3 Sample impression
4 Clinical management
CAD-RADS provides branching management pathways depending on whether the patient presents with stable or acute chest pain.
Stable chest pain
| Category | Recommendation |
|---|---|
| CAD-RADS 0 | Reassurance; consider non-atherosclerotic causes of chest pain. |
| CAD-RADS 1 & 2 | Preventive therapy and risk-factor modification per guidelines. |
| CAD-RADS 3 | Functional assessment (stress test or CT-FFR) to determine if the moderate lesion is flow-limiting. |
| CAD-RADS 4A | ICA or functional assessment. |
| CAD-RADS 4B | ICA strongly recommended. |
| CAD-RADS 5 | ICA or functional / viability assessment. |
Acute chest pain
| Category | ACS likelihood | Recommendation |
|---|---|---|
| CAD-RADS 0 & 1 | Highly unlikely | Consider non-ACS etiologies; outpatient follow-up. |
| CAD-RADS 2 | Unlikely | Outpatient follow-up — but if clinical suspicion is high or the V modifier is present, admit and consult cardiology. |
| CAD-RADS 3 | Possible | Admit; cardiology consult; functional testing and/or ICA. |
| CAD-RADS 4 & 5 | Likely / very likely | Admit; cardiology consult; expedite ICA and appropriate revascularization. |