A 55-year-old man with chest pain and elevated troponin undergoes CT coronary angiography (CTCA). A plaque is identified in the LAD with a CT attenuation value of -40 HU within the plaque core. What type of plaque is this, and what is its clinical significance?
- A Lipid-rich necrotic core (LRNC) / low-attenuation plaque — vulnerable plaque with high rupture risk ✓
- B Calcified plaque — stable; lower risk of rupture
- C Fibrous plaque — intermediate attenuation
- D Spotty calcification only — benign variant
Correct answer: A. Lipid-rich necrotic core (LRNC) / low-attenuation plaque — vulnerable plaque with high rupture risk
Explanation
Low-attenuation plaque (LAP) — defined as CT attenuation <30 HU within the plaque — corresponds histologically to a lipid-rich necrotic core (LRNC), a major component of vulnerable/high-risk plaques prone to rupture and acute coronary syndrome. CTCA high-risk plaque features include LAP (<30 HU), napkin-ring sign, positive remodeling, and spotty calcification. Calcified plaques (>130 HU) are stable. Fibrous plaques have intermediate attenuation (60–130 HU). This patient's plaque at -40 HU represents a fatty/necrotic core.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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