Coronary Artery CT Low-Density Plaque Area and Its Ratio to the Whole Area of a Non-Calcified Plaque at the Culprit Lesion in Patients With Unstable and Stable Coronary Artery Disease

Intravascular ultrasound studies have shown that patients with unstable angina pectoris (UAP) more frequently had soft plaques in the culprit coronary arteries than patients with stable angina pectoris (SAP). We evaluated coronary plaque characteristics of culprit lesions in patients with UAP by 64-slice computed tomographic coronary angiography (64-slice CTCA). 64-slice CTCA (Aquilion 64, Toshiba Medical Systems, Otawara, Japan) was performed in 30 patients (UAP = 14, SAP = 16) before percutaneous coronary intervention (PCI). Coronary plaque area was measured by manual tracing for the difference between the area within the external elastic membrane and the area of the vessel lumen at the site of maximal luminal narrowing as observed on a cross-sectional 64-slice CTCA image where PCI was performed. Within this plaque area, CT low-density plaque area (< 50 Hounsfield units) was automatically calculated. There were no differences in stenotic rate and whole plaque area of the culprit lesion between patients with UAP and SAP. However, the CT low-density plaque area was significantly greater in patients with UAP than in those with SAP. A greater area of CT low-density plaque in the culprit lesion is associated with UAP rather than SAP. Measuring CT-low density plaque area on 64-slice CTCA images could be useful for understanding the clinical setting of UAP.