Decoding the Coronaries

CAD-RADS, or the Coronary Artery Disease Reporting and Data System, is a standardized reporting system designed to enhance the communication of coronary artery disease (CAD) findings from imaging studies. CAD-RADS represents a significant step towards a more systematic and evidence-based approach to the management of CAD. By standardizing reporting, guiding clinical decisions, facilitating research, and improving risk stratification, CAD-RADS not only holds the potential to improve the clarity of communication between the diagnostician and the downstream physician, but at a larger scale, it could contribute significantly to better cardiovascular health outcomes across populations.

Why CAD-RADS?

CAD-RADS was developed to establish a clear and consistent framework for reporting coronary artery disease findings from coronary computed tomography angiography (CCTA).

Prior to CAD-RADS, the reporting of coronary computed tomography angiography (CCTA) findings often lacked uniformity. This variability made it challenging for referring physicians to interpret results consistently and make informed decisions about patient care.

CAD-RADS was initially created in 2016, as a result of a collaboration between the Society for Cardiovascular Computed Tomography (SCCT), the American College of Radiology (ACR), and the North American Society for Cardiovascular Imaging (NASCI). Subsequently it was also endorsed by the American College of Cardiology (ACC). CAD-RADS introduced a standardized classification system, providing a common language for radiologists, cardiologists and referring physicians, facilitating a more consistent understanding of CCTA results across different institutions and regions.

The system was then updated to CAD-RADS 2.0 in 2022 to incorporate several methods for the categorization including descriptors of overall coronary plaque burden, with additional options to include CT-FFR (CT fractional flow reserve) or myocardial CT perfusion results for the assessment of lesion-specific ischemia if obtained. It also now includes the description of non-atherosclerotic coronary abnormalities as a separate modifier “E” for exceptions.

• CAD-RADS reporting ensures that all imaging studies are reported in a uniform manner, making it easier for referring physicians to interpret results. The use of clear categories (ranging from CAD-RADS 0 to CAD-RADS 5) allows for quick assessment of the severity of coronary artery disease. The incorporation of P1 to P4 descriptors into the CAD-RADS framework serves to provide a more nuanced understanding of plaque burden. Each descriptor corresponds to a specific level of plaque accumulation, allowing for a more detailed assessment of a patient's coronary artery health. 

Since the original CAD-RADS have been developed in 2016, many technological advancements to CCT have been incorporated into routine practice and correspondingly, CAD-RADS guidelines have also been updated.

The latest updates to CAD-RADS 2.0 have focused on improving the specificity of reports and providing clear recommendations for patient management.

As the framework gets more comprehensive, it is unavoidable that it becomes more complex and therefore more time-consuming as well.

Nevertheless, by incorporating CAD-RADS into risk assessment, clinicians can better identify individuals at higher risk who may benefit from more intensive preventive therapies or closer monitoring, potentially improving long-term population health outcomes.

The integration of AI with CAD-RADS represents a significant advancement in cardiac imaging. AI can assist in automating the categorization of findings according to CAD-RADS criteria, reducing the potential for human error and ensuring consistency in reporting. Furthermore, AI-driven analytics can provide additional insights into patient data, enabling more personalized treatment plans and improving patient outcomes. At the same time, the stratification of CAD-RADS can aid the training of AI models that might lead to a better validated approach to cardiovascular risk prediction beyond traditional expert consensus approaches.

Beyond Stenosis: Understanding the CAD-RADS Categories

CAD-RADS isn't solely about quantifying luminal narrowing. It's a comprehensive system that categorizes CCTA findings based on the likelihood of causing myocardial ischemia. This risk stratification allows for more tailored management strategies.

The updated CAD-RADS 2.0 classifications follow a now well-established framework, while adding more detailed descriptors and modifiers to augment each CAD-RADS category. This added context improves clarity, helps referring physicians understand the implications of the findings. 

The system labels findings into distinct levels, ranging from CAD-RADS 0 to CAD-RADS 5 as core categories, allowing healthcare providers to quickly assess the severity of coronary artery disease and make informed decisions regarding patient management.

• CAD-RADS 0: No evidence of coronary artery disease. This category indicates that the coronary arteries are normal, and there are no significant findings on the imaging study.
• CAD-RADS 1: Minimal non-obstructive CAD (1-24% stenosis).This category suggests the presence of coronary artery disease without significant stenosis, meaning that there are no blockages that would impede blood flow. Typically managed with lifestyle modifications and risk factor optimization.
• CAD-RADS 2: Mildly obstructive coronary artery disease (25-49% stenosis). This indicates that there is a presence of stenosis (narrowing of the arteries), which may require monitoring but typically does not necessitate immediate intervention. Clinical context becomes crucial here. Further non-invasive testing may be considered based on symptoms and risk profile.
• CAD-RADS 3: Moderately obstructive coronary artery disease (50-69% stenosis). This category suggests a higher risk for adverse cardiac events and often leads to further evaluation or intervention. Stress testing is generally recommended to assess functional significance.
• CAD-RADS 4A: High-grade stenosis (≥70% stenosis) in ≤2 proximal segments. Functional assessment or invasive coronary angiography (ICA) is usually indicated.
• CAD-RADS 4B: Moderate-to-severe stenosis (≥50% stenosis) in the left main artery, or 3-vessel disease with severe stenosis (≥70% stenosis). ICA is strongly recommended.
• CAD-RADS 5: Total occlusion. Coronary artery disease with high-risk features. This category includes findings that suggest a high likelihood of significant coronary artery disease, such as extensive calcification or high-risk plaque characteristics. Requires further evaluation, often with ICA, to determine viability and potential for revascularization.
• CAD-RADS N: Non-diagnostic study. This highlights technical limitations of the study whereby obstructive CAD cannot be excluded, necessitating repeat imaging or alternative modalities.

Plaque Amount Assessment

While the primary CAD-RADS category provides a strong foundation, the system's true strength lies in its descriptors and modifiers.

The recent incorporation of P1 to P4 descriptors into the CAD-RADS 2.0 framework serves to provide a more nuanced understanding of the overall plaque burden. A unique quality of cardiac CT when compared with other non-invasive tests, is its ability to not only detect the presence but also allow for the measurement of the amount of plaque present. It is now well established that beyond the existence or absence of anatomical stenosis, the overall amount of coronary plaque has a strong association with the incidents of coronary heart disease events and therefore the inclusion of P descriptors may, indeed, offer stronger prognostic value.

P1 Descriptor

• Definition: Mild plaque burden.
• Implication: Indicates the presence of non-obstructive plaque, suggesting a lower risk of significant coronary artery disease.

P2 Descriptor

• Definition: Moderate plaque burden.
• Implication: Reflects the presence of some plaque that may warrant monitoring but is not yet obstructive.

P3 Descriptor

• Definition: Severe plaque burden.
• Implication: Suggests a higher risk of coronary artery disease, with potential for obstructive lesions that may require intervention.

P4 Descriptor

• Definition: Extensive plaque burden.
• Implication: Indicates significant plaque accumulation with a high likelihood of obstructive disease, necessitating immediate clinical attention.

The addition of P1 to P4 descriptors to the CAD-RADS categories enhances the ability to assess and communicate the severity of plaque burden in patients. This improvement not only aids in the diagnosis and management of coronary artery disease but also supports more personalized patient care strategies. Understanding these descriptors is crucial for healthcare professionals involved in cardiovascular imaging and treatment.

The Power of Modifiers: Adding Clinical Context

Modifiers provide additional context for the findings, going beyond just the severity of stenosis and the overall amount of plaque, to include other relevant factors. In addition to a specific level of plaque accumulation, allowing for a more detailed assessment of a patient's coronary artery health, these crucial modifiers incorporate additional information that may significantly impact clinical decision-making:

• N (Non-diagnostic): Indicates that the study is not fully evaluable or non-diagnostic, which may be due to motion artifacts or other technical issues.
• HRP (High-Risk Plaque):  In CAD-RADS 2.0, HRP replaces the previous "Vulnerable Plaque" designation from the original CAD-RADS and indicates the presence of specific plaque features that may be more likely to cause plaque rupture and subsequent events. The presence of such presentations as positive remodeling, low attenuation plaque, napkin-ring sign, and spotty calcification elevates risk and may warrant more aggressive management even in non-obstructive lesions.
• I (Ischemia):  indicates that either a CT-FFR or CTP was performed. The “I” modifier has three options:
  • "I+" = Ischemia present
  • "I-" = No ischemia detected
  • "I+/-" = Ischemia results indeterminate 
• S (Stent):  Indicates the presence of stents in the coronary arteries.
• G (Graft):  Indicates the presence of coronary artery bypass grafts.
• E (Exceptions):  Denotes potential coronary abnormalities not due to atherosclerotic plaque buildup, such as compression or stenosis caused by other factors like anomalous coronary arteries or dissection.

By consistently utilizing these modifiers, CAD-RADS classification moves beyond simply reporting stenosis percentages and paints a more complete picture of the patient's atherosclerosis and the overall coronary burden and risk. The information provided by modifiers can help guide patient management decisions, such as the need for invasive angiography or revascularization. As CAD-RADS continues to evolve, there is a high likelihood of more specific modifiers being incorporated in the future as well.

Importance of CAD-RADS in Clinical Practice

The true value of CAD-RADS lies in its seamless integration into daily clinical practice. Consider these practical implications:

• Standardization: By providing a uniform reporting system, CAD-RADS enhances communication among healthcare providers, ensuring that everyone involved in a patient's care understands the severity of their condition.
• Multidisciplinary Collaboration: Discussion of complex CAD-RADS findings should be a routine part of cross-specialty team meetings to leverage the expertise of interventional cardiologists, cardiac surgeons, and imaging specialists. CAD-RADS can serve as a quantified “lingua franca” in these team discussions. CAD-RADS should be a critical pillar of peer-review, quality assurance and continuing education in CAD diagnosis and therapy planning.
• Guided Management: The clear categorization of findings helps clinicians determine the appropriate management strategies for patients, from medication, lifestyle modifications to invasive procedures.
• Risk Stratification: Utilizing CAD-RADS categories and modifiers in conjunction with clinical presentation, risk factors, and other diagnostic tools can guide further testing and treatment strategies.
• Patient Communication: CAD-RADS provides a framework for explaining CCTA findings to patients in a clear and understandable manner, fostering shared decision-making. Using the power of “an image worth a thousand words” combined with quantified measurements, can facilitate an understanding of the severity of the clinical condition and the importance of adhering to the prescribed management routine. 
• Improved Patient Outcomes at Scale: Standardized diagnostic reporting can facilitate following CAD at the population health level. By assisting with timely and accurate diagnosis and treatment, CAD-RADS can contribute to better patient outcomes and reduced morbidity associated with coronary artery disease. 

In essence, CAD-RADS represents a significant step towards a more systematic and evidence-based approach to the management of CAD. By standardizing reporting, guiding clinical decisions, facilitating research, and improving risk stratification, CAD-RADS has the potential to contribute to better cardiovascular health outcomes across populations. The ongoing updates to CAD-RADS, such as the introduction of CAD-RADS 2.0 incorporating plaque burden assessment and high-risk plaque features, further underscore its evolving role in optimizing patient care and population health.

CAD-RADS is a vital tool in the assessment and management of coronary artery disease. By standardizing the reporting of imaging findings, it enhances communication among healthcare providers and guides clinical decision-making.

Looking Ahead:

As the understanding of coronary artery disease continues to evolve, CAD-RADS will remain an essential component in the care of patients at risk for cardiovascular events.

The recent developments incorporated into CAD-RADS 2.0 have already significantly enhanced the communication of test results between radiologists and referring physicians. By providing standardized, clear, and actionable reports, CAD-RADS facilitates better patient management and outcomes. As these advancements continue to evolve, they promise to further improve the quality of care for patients with coronary artery disease.

To learn more about CAD-RADS and how to incorporate them into your practice, visit https://www.circlecvi.com/cardiac-ct#reporting

Despite the promising developments in CAD-RADS and AI-based post-processing systems, several challenges remain. These include the need for robust validation of AI algorithms, ensuring interoperability and standardization between different systems, in addition to the ever-present concerns related to data privacy and security. Future research should focus on overcoming these obstacles while continuing to refine CAD-RADS and exploring the role of new AI applications in cardiac imaging.

As CCTA technology advances, so too will CAD-RADS. We can anticipate further refinement of the categories and modifiers, potentially incorporating artificial intelligence and machine learning to enhance risk prediction and personalized management.

For any healthcare professionals, familiarizing themselves with CAD-RADS, embracing its comprehensive framework and utilizing its modifiers thoughtfully, can unlock its full potential and help navigate the complexities of coronary imaging with greater confidence and precision.