CAD-RADS™ 2.0 – 2022 Coronary Artery Disease Expert Consensus

• Coronary CT angiography (CCTA) has seen technical advancements and clinical validation over the last decade.
• Professional societies have issued guidelines, expert consensus documents, and Appropriateness Criteria for CCTA.
• Training is essential for physicians and technologists in image acquisition and interpretation to ensure quality.
• Standardized reporting approaches are needed to decrease variability and ensure appropriate use of test results.

CAD-RADS 2.0 Update

• The CAD-RADS classification of coronary artery disease for patients undergoing CCTA has been updated as of 2022.
• The update includes plaque burden, ischemia features, and recent clinical trial evidence and guidelines.
• The 2022 CAD-RADS 2.0 classification follows a framework of stenosis, plaque burden, and modifiers.
• It now also has the option to include ischemia evaluation by CT fractional-flow-reserve (CT-FFR) or myocardial CT perfusion (CTP), if performed.
• The most severe coronary artery luminal stenosis remains the central component, providing the numeric descriptor.
• Methods to estimate, quantify, and report overall plaque burden are included.
• Additions aim to enhance patient management decisions following CCTA.

Goals of CAD-RADS

• Remains to standardize reporting of CCTA results.
• Facilitate communication of test results to referring physicians and provide suggestions for patient management.
• Should not replace the impression section of the report provided by the reading physician.
• It provides a complementary assessment and should be interpreted with detailed patient-specific information.
• Clinical management suggestions should not replace clinical judgment due to patient-specific factors.

Clinical Value and Validation

• CAD-RADS classification accurately predicts major adverse cardiovascular events (unstable angina, myocardial infarction, or death) in stable chest pain patients.
• CAD-RADS has superior performance compared to traditional risk factors, risk stratification scores, Coronary Artery Calcium Score (CAC), and earlier SCCT coronary stenosis scoring system.
• Correlates with stenosis degree measured by invasive coronary angiography (ICA) with high diagnostic accuracy.
• Adoption in clinical practice results in reduced downstream testing and cardiology referral rates in non-obstructive coronary artery disease patients.
• Has a favorable impact on medical therapy and systolic blood pressure control.
• Deep learning algorithms have been validated for CAD-RADS classification evaluation on CCTA.
• CAD-RADS has widespread adoption in clinical practice, especially in the United States.
• CAD-RADS offers a clinically useful categorization of coronary artery disease with high diagnostic accuracy versus invasive angiography.
• It has robust prognostic value and beneficial impact on medical management.

Clinical Trials

• PROMISE and SCOT-HEART trials demonstrated that CCTA is clinically useful as an alternative to functional testing (PROMISE) or in addition to standard of care (SCOT-HEART).
• CAD-RADS classification has confirmed prognostic value, with higher scores associated with increased risks of fatal and non-fatal MI.
• CT-STAT, ACRIN-PA, ROMICAT II, and CT-COMPARE trials compared CCTA to standard of care in acute chest pain patients.
• CCTA supported discharging patients from the emergency department based on a negative CCTA.
• Guidelines support CCTA use in low to intermediate risk patients with acute chest pain presenting to the emergency department.
• CCTA is now a first-line test (Class I) for acute and chronic coronary syndromes according to the European Society of Cardiology, NICE guideline, and the new American College of Cardiology and American Heart Association Chest Pain Guideline.
• There have been advances in detecting, quantifying, and understanding atherosclerotic plaque burden by CCTA.
• There is a better understanding of clinical implications of various CCTA findings.

Optimal Clinical Management

• There is insufficient prospective randomized clinical trial data to support the optimal clinical management strategy following CCTA.
• CAD-RADS classification is an expert consensus document based on available research data from clinical trials and broad expert consensus.
• Recommendations for further patient management need to be interpreted in the context of other available clinical information.

CAD-RADS Reporting System

• Based on stenosis severity and plaque burden.
• Uses a classification system originally developed by the Society of Cardiovascular Computed Tomography.
• Assessment includes overall plaque burden (P1 to P4) and ischemia classification (I+, I−, I+/–).

CAD-RADS Categories 3, 4, and 5

• Require further consideration.
• CAD-RADS 3 (moderate stenosis): consider CT-FFR, CTP, or stress testing to document or exclude ischemia.
• In CAD-RADS 3, further testing should be considered if it will change patient management.
• Additional factors to consider are lesion location, severity, and high-risk plaque features.
• Invasive coronary angiography requires integration of clinical, imaging, and stress test findings.
• CAD-RADS 4 recommendations vary depending on left main coronary artery involvement and severe three-vessel disease (>70%).
• CAD-RADS 4A: single or two vessels with severe stenosis, needs further evaluation with ICA or functional imaging.
• CAD-RADS 4B: left main stenosis of at least 50% or three-vessel obstructive disease (>70%), needs further evaluation with ICA and possible revascularization.
• CAD-RADS 5 (total coronary occlusion): clinical relevance varies, factors such as lesion length, calcification, tortuosity, and collateralization influence management decisions.
• Similar framework used for acute chest pain patients, considering clinical symptoms, troponin levels, EKG changes, and high-risk plaque features.

Plaque Burden Sub-classification

• Utilizes the designation “P” with categories ranging from P1 to P4 to categorize the amount of plaque as mild, moderate, severe or extensive on a per-patient basis.
• CAD-RADS 0 means there is no stenosis or plaque, therefore P0 is not required as a classification.
• There is currently no single method that is used to quantify the overall amount of plaque.
• Assessment of plaque burden within an individual patient may vary substantially depending upon the method applied.
• May lower the reproducibility of such an assessment.

Methods for Reporting Total Coronary Plaque Burden

• CAC provides a reproducible, and accurate method to quantify the amount of calcified plaque burden.
• CAC testing (most commonly quantified according to the Agatston method) can be used to identify the overall amount of plaque.
• Calcium score should not be used in isolation and should be combined with at least a qualitative assessment of total plaque burden (calcified and non-calcified).
• Therefore, the plaque burden and “P” category based on Calcium score will stay the same (if no non-calcified plaque is seen) or may increase after incorporating information on the total burden of non-calcified plaque.
• Segment involvement score (SIS): assigns a score of 1 for each of the 16 coronary segments with any detectable plaque.
• Visual estimate of overall plaque burden: qualitative estimate of calcified and non-calcified plaque in each coronary vessel to assess overall plaque burden.
• Quantitative Assessment of Total Coronary Plaque: various quantitative approaches are available to quantify total coronary plaque volume on CCTA.
• Giving options to estimate overall plaque burden is important to facilitate routine assessment of plaque burden.
• CAD-RADS recommendations for patient management using plaque assessment are mostly based on expert opinion.
• Aggressive therapies are suggested for individuals with a higher plaque burden.

Modifiers

• Complement CAD-RADS categories to indicate a study is not fully evaluable or non-diagnostic (N), or to indicate the presence of stents (S), grafts (G), and high-risk plaque (HRP).
• The panel has added two new modifiers: ischemia (I) and exceptions (E).
• The term “vulnerable plaque (V)” has now been replaced with “high risk plaque (HRP)” to be consistent with evolving terminology.

Modifier N – Non-Diagnostic Study

• "N" can be used as a modifier or as a CAD-RADS category, depending on context.
• If the study is not fully diagnostic, due to motion artifacts, calcium blooming, metal artifacts or other types of artifacts.
• Category “P” should be used with category or modifier “N”, if total coronary plaque assessment can be performed reliably.

Modifier S = Stent

• indicates the presence of at least one coronary stent anywhere in the coronary system.

Modifier G = Grafts

• indicates the presence of at least one coronary-artery bypass graft.

High-Risk Plaque (HRP) Features

• Indicate a higher risk of future ACS as well as lesion-specific ischemia.
• Include positive remodeling, low-attenuation plaque, spotty calcification, and the napkin-ring sign.
• If a coronary plaque clearly demonstrates two or more high-risk features by CCTA, the modifier “HRP” (high risk plaque) should be added.
• High-risk features include: spotty calcifications, low attenuation plaque (less than 30 Hounsfield units), positive remodeling, and the “napkin ring sign".

Modifier I = Ischemia

• Can be added when CT-FFR or CTP is performed.

CT-FFR

• Modifier I+ lesions with abnormal CT-FFR (≤ 0.75) in a vessel large enough for PCI.
• Modifier I- when lesion-specific CT-FFR > 0.80.
• Modifier I+/- for values between 0.76 and 0.80.

Myocardial CT Perfusion

• Modifier “I+” should be added to CAD-RADS in the presence of myocardial ischemia (reversible perfusion defect) or peri-infarct ischemia (perfusion defect during stress larger than rest perfusion defect).
• If no ischemia is detected or if presence of a prior fixed myocardial infarct, then Modifier “I−” will be added to CAD-RADS.
• Modifier “I+/-” indicates that the study is borderline or inconclusive for the presence of ischemia.

Modifier E = Exceptions

• Used for non-atherosclerotic causes of coronary abnormalities.
• Includes coronary dissections, anomalous coronary arteries, aneurysms, vasculitis, fistulas, and extrinsic compression.
• Added at the end of the score as a modifier.

Framework for New CAD-RADS Coding

• Stenosis, plaque, and modifiers.
• Category “P” for plaque follows the CAD-RADS score for stenosis.
• Modifiers are added, if present, in a specific order.
• Order: N (non-diagnostic), HRP (high-risk plaque), I (ischemia), S (stent), G (graft), E (exceptions).

Other Cardiac or Extra-cardiac Findings

• Should be reported in the body or impression of the CCTA report.
• Specific follow-up and recommendations should be included depending on the pathology.

Discussion

• CAD-RADS has been developed based on scientific data, consensus guidance from cardiac imaging experts and a multi-disciplinary effort involving societies comprised of radiologists and cardiologists (SCCT, ACR, ACC and NASCI).
• CAD-RADS is intended to be a “living document”.

Conclusion

• Enhances the initial standardized reporting system for CCTA.
• Includes data from recent large trials, new clinical guidelines, and by adding features of plaque burden and lesion physiology determined from cardiac CT.
• The updated CAD-RADS classification follows a framework of stenosis, plaque burden and modifiers which now also include ischemia evaluation by CT-FFR or myocardial CT perfusion, when applicable.