Vulnerable plaques are lesions at high risk for near-term rupture. The majority of acute coronary events are actually caused by the rupture of plaques that were previously non-stenotic — which is why stenosis severity alone is an unreliable predictor of MI.
Histologically, vulnerable plaques typically feature:
- A large lipid-rich necrotic core
- Macrophage infiltration
- Plaque vascularization (neovascularization)
- A very thin fibrous cap (< 65 µm)
On CCTA, a plaque is deemed vulnerable (and assigned the CAD-RADS V modifier) if it exhibits at least two of the following four high-risk features:
Also known as the Glagov effect — the outer vessel wall expands outward to maintain the luminal area as plaque builds up. Quantitatively: the arterial diameter at the plaque site must be ≥ 1.1 × the average of the adjacent normal proximal and distal segments.
Represents the necrotic core. Defined by a dark attenuation of < 30 HU.
A small, punctate speck of calcification found within a predominantly non-calcified plaque — often forming on the nidus of the necrotic core.
A ring-like rim of high attenuation surrounding a central area of dark, low attenuation.
For the full CAD-RADS reporting system including how the V modifier is combined with category and other modifiers, see CAD-RADS 2.0 reporting.