Carotid Plaque Morphological Classification Compared With Biomechanical Cap Stress
Implications for a Magnetic Resonance Imaging–Based Assessment
Background and Purpose—Two approaches to target plaque vulnerability—a histopathologic classification scheme and a biomechanical analysis—were compared and the implications for noninvasive risk stratification of carotid plaques using magnetic resonance imaging were assessed.
Methods—Seventy-five histological plaque cross sections were obtained from carotid endarterectomy specimens from 34 patients (>70% stenosis) and subjected to both a Virmani histopathologic classification (thin fibrous cap atheroma with <0.2-mm cap thickness, presumed vulnerable) and a peak cap stress computation (<140 kPa: presumed stable; >300 kPa: presumed vulnerable). To demonstrate the implications for noninvasive plaque assessment, numeric simulations of a typical carotid magnetic resonance imaging protocol were performed (0.62×0.62 mm2 in-plane acquired voxel size) and used to obtain the magnetic resonance imaging–based peak cap stress.
Results—Peak cap stress was generally associated with histological classification. However, only 16 of 25 plaque cross sections could be labeled as high-risk (peak cap stress>300 kPa and classified as a thin fibrous cap atheroma). Twenty-eight of 50 plaque cross sections could be labeled as low-risk (a peak cap stress<140 kPa and not a thin fibrous cap atheroma), leading to a κ=0.39. 31 plaques (41%) had a disagreement between both classifications. Because of the limited magnetic resonance imaging voxel size with regard to cap thickness, a noninvasive identification of only a group of low-risk, thick-cap plaques was reliable.
Conclusions—Instead of trying to target only vulnerable plaques, a more reliable noninvasive identification of a select group of stable plaques with a thick cap and low stress might be a more fruitful approach to start reducing surgical interventions on carotid plaques.
- Received April 8, 2015.
- Revision received April 8, 2015.
- Accepted April 21, 2015.
- © 2015 American Heart Association, Inc.