Vulnerable plaque

Vulnerable or high-risk plaque refers to coronary artery atherosclerotic lesions with features associated with future acute coronary events, independent of luminal stenosis.

Clinical presentation

The relevant clinical sequelae of vulnerable plaque are acute coronary syndromes, which present as unstable angina, acute myocardial infarction, or sudden cardiac death.

Pathology

Acute coronary syndromes usually result from sudden coronary thrombosis, which in turn is most commonly due to deposition of cholesterol in the coronary subendothelium leading to plaque formation and its rupture, followed by erosion and, uncommonly, calcified nodules . The so-called vulnerable or high-risk plaque represents the postulated precursor lesion for coronary thrombosis. Histological features include a necrotic lipid-rich core, thin-cap fibroatheroma, positive remodeling of the vessel, and spotty calcification .

Radiographic features

CT

There are 4 main vulnerable plaque features on coronary CTA :

• positive remodeling
  • outer vessel diameter at the plaque ≥1.1 times that of adjacent uninvolved vessel, assessed on long-axis and short-axis reformatted images
• low attenuation plaque
  • noncalcified plaque measuring <30 HU
• napkin-ring sign
  • peripheral higher attenuation of the noncalcified portion of the plaque
• spotty calcium
  • small calcified plaque (density ≥130 HU separately visualized from the lumen, diameter <3 mm in any direction, but also length <1.5 times vessel diameter and width <2/3 times vessel diameter)

Radiology report

In reporting coronary CTAs using the Coronary Artery Disease - Reporting and Data System, patients with at least 1 high-risk plaque feature can be indicated with the modifier "V." For example, if a patient's most severe lesion is mildly stenotic with vulnerability, the study is reported as CAD-RADS 2/V.