Abstract 12904: Aggregate Plaque Volume by Coronary CT Angiography to Define Lesion-Specific Ischemia: A Direct Comparison to Fractional Flow Reserve

Abstract

Background: Invasive coronary angiography with fractional flow reserve (FFR) has been widely used for physiologic assessment of intermediate coronary artery disease (CAD) lesions (30-70% luminal diameter stenosis). We aimed to determine whether coronary atherosclerotic plaque features by coronary CT angiography (CCTA) effectively predicted lesion-specific ischemia as compared to FFR in CCTA-identified intermediate lesions.

Methods: Twenty-seven patients with suspected or known CAD who were identified as having intermediate stenosis by CCTA and underwent invasive coronary angiography and FFR were studied. Coronary vessels interrogated by FFR (n=28) were selected for manual CCTA plaque measurements by 2 readers and included diameter stenosis (DS, %), area stenosis (AS, %), minimal luminal diameter (MLD, mm), minimal luminal area (MLA, mm²) and plaque burden. Plaque burden was defined by aggregate plaque volume (APV) (mm³), obtained by summation of contiguous plaque areas and multiplication by the slice increment (0.5 mm) from the coronary artery ostium to the distal portion of the lesion assessed by FFR, and reported as APV% (plaque volume/vessel volume x 100). CCTAs and FFR data were analyzed by independent core laboratories.

Results: Mean plaque volume was 390.3±158.7 mm³; FFR averaged 0.83±0.1, and 10 lesions had an abnormal FFR (<0.8). Significant correlations were observed between FFR and CCTA DS (r=−0.43, p=0.02), AS (r=−0.47, p=0.01), MLD (r=0.47, p=0.01), MLA (r=0.52, p=0.005), and APV% (r=−0.56, p=0.002). Compared to vessels without ischemia, vessels with ischemia had greater APV% (50.5 vs. 41.8%, p=0.006); with no significant differences in DS, AS, MLD and MLA (54.4 vs. 47.4%, p=0.3; 63.2 vs. 47.8%, p=0.06; 1.4 vs. 1.7mm, p=0.2; 2.8 vs. 4.4mm², p=0.2). Area under the receiver operating characteristic curve for coronary lesion-specific ischemia was 0.66, 0.71, 0.68, 0.81 and 0.79 for DS, AS, MLD, MLA and APV%, respectively.

Conclusions: As compared to individual measures of DS, AS, MLD and MLA, % aggregate coronary plaque volume demonstrates superior identification and discrimination of ischemia-causing lesions.