Arterio-arterial embolism is a primary mechanism underlying ischemic stroke associated with large vessel disease (LVD). Most expert recommendations and guidelines for stroke prevention in patients with atherosclerotic carotid artery disease primarily focus on the degree of stenosis. Carotid artery plaque morphology and composition are increasingly recognized as critical factors in stroke risk, yet standardized classification for atherosclerotic carotid plaques remains underdeveloped. Recently, the Plaque-RADS classification system has been proposed to address this gap (Sabas et al.), offering a consistent approach to evaluating plaque features beyond stenosis degree. By incorporating imaging from ultrasound, CTA, and MRI, Plaque-RADS facilitates the standardized reporting of carotid plaques, aiming to enhance stroke risk assessment and inter-professional communication. This system draws on principles from other RADS frameworks (e.g., BI-RADS), categorizing plaque severity from Grade 1 (no plaque) to Grade 4 (complicated plaques).
- Plaque-RADS 1: No plaque or atherosclerosis, indicating no cerebrovascular risk.
- Plaque-RADS 2: Low-risk eccentric plaques with minor calcifications or lipid pools (<3 mm).
- Plaque-RADS 3: Moderate-risk plaques (≥3 mm), often with lipid-rich necrotic cores or thin fibrous caps. Subtypes (3a, 3b, 3c) account for cap thickness and presence of ulceration.
- Plaque-RADS 4: High-risk complicated plaques, including features such as intraplaque hemorrhage (IPH), ruptured fibrous caps, or intraluminal thrombus. Subtypes (4a, 4b, 4c) specify these high-risk characteristics.
Ancillary features such as inflammation, neovascularization, or plaque progression, and diagnostic modifiers (e.g., image quality, stents) further refine this system, promoting robust data collection for research and clinical application. Integrating Plaque-RADS with stenosis measures might assist clinicians in optimizing personalized stroke prevention strategies.
Recent studies by Kopczak et al. (2020, 2022) underline the critical role of complicated carotid artery plaques (cCAPs), especially in cryptogenic stroke (CS). The 2020 study, part of the Carotid Plaque Imaging in Acute Stroke (CAPIAS) project, used high-resolution MRI to assess non-stenosing carotid plaques in 196 patients with ischemic stroke in the anterior circulation. Findings showed that cCAPs, defined by IPH, fibrous cap rupture, or mural thrombus (AHA Type VI plaques), were significantly more prevalent ipsilateral to the stroke (31% vs. 12%). These plaques were also more common in CS than in other stroke subtypes, suggesting their importance in embolic stroke mechanisms, even in the absence of significant stenosis.
The 2022 study built on these findings by linking cCAPs to an increased risk of recurrent ischemic stroke or TIA. Over three years, patients with ipsilateral cCAPs had a 5.6-fold higher risk of recurrence, particularly when features like ruptured fibrous caps or IPH were present. This emphasizes that plaque composition, rather than stenosis severity, should be central to stroke risk assessment. Advanced carotid plaque imaging could thus play a pivotal role in identifying high-risk individuals for targeted prevention strategies.
Both studies emphasize the need for a more nuanced evaluation of carotid plaques, focusing on high-risk characteristics like IPH and ruptured fibrous caps, to refine stroke prevention approaches.
Key Points:
- Traditional stroke risk assessment focused mainly on stenosis degree, but plaque morphology and composition are now recognized as crucial factors.
- Plaque-RADS is a new standardized classification system for carotid artery plaques, grading them from 1 (no plaque) to 4 (complicated plaques), incorporating multiple imaging modalities.
- Complicated carotid artery plaques (cCAPs) are significantly more common on the stroke side (31%) compared to the non-stroke side (12%), particularly in cryptogenic stroke cases.
- Patients with ipsilateral cCAPs have a 5.6-fold higher risk of recurrent stroke or TIA over three years.
References:
1. Saba L, Cau R, Murgia A, et al. Carotid Plaque-RADS: A Novel Stroke Risk Classification System. JACC Cardiovasc Imaging. 2024;17(1):62-75. doi:10.1016/j.jcmg.2023.09.005
2. Kopczak A, Schindler A, Bayer-Karpinska A, et al. Complicated Carotid Artery Plaques as a Cause of Cryptogenic Stroke. J Am Coll Cardiol. 2020;76(19):2212-2222. doi:10.1016/j.jacc.2020.09.532.
3. Kopczak A, Schindler A, Sepp D, et al. Complicated Carotid Artery Plaques and Risk of Recurrent Ischemic Stroke or TIA. J Am Coll Cardiol. 2022;79(22):2189-2199. doi:10.1016/j.jacc.2022.03.376.
Co-authors:
Nathalie Nasr, Department of Neurology, University Hospital and University of Poitiers, France
Markus Kneihls, Department of Neurology, Medical University of Graz, Austria
Publish on behalf of the Scientific Panel on Neurosonology