Incremental Value of Subtended Myocardial Mass for Identifying FFR-Verified Ischemia Using Quantitative CT Angiography: Comparison With Quantitative Coronary Angiography and CT-FFR

Abstract

Objectives: This study examined the incremental value of subtended myocardial mass (V_sub) as assessed by coronary computed tomography angiography (CTA) for identifying lesion-specific ischemia verified by invasive fractional flow reserve (FFR) in quantitative coronary CTA.

Background: FFR is determined not only by coronary stenosis severity, but also by V_sub. One-step evaluation of combined V_sub and coronary lesion morphology may improve the accuracy of coronary CTA for identifying ischemia-producing lesions.

Methods: A total of 246 intermediate coronary artery lesions (30% to 80% diameter stenosis) in 220 patients (mean age 61.7 years, 168 men) interrogated by FFR were retrospectively studied. Coronary CTA data were used to assess the V_sub by coronary artery stenosis, minimal lumen area (MLA), percentage of aggregated plaque volume (%APV), positive remodeling, and low-attenuation plaque. The ability of V_sub/MLA² to discriminate lesions with FFR ≤0.80 was examined. Diagnostic performance, odds ratios, and category-less net reclassification improvements of coronary CTA parameters for FFR-verified (≤0.80) ischemia were evaluated. On-site computed tomography (CT) derived-FFR (CT-FFR) and quantitative coronary angiography (QCA) data were also compared.

Results: Of 246 lesions, 84 (34.1%) showed an FFR ≤0.80. V_sub was independently associated with an FFR ≤0.80 (odds ratio: 1.04/1 cm³; p = 0.032) and showed incremental value over MLA. V_sub/MLA² >4.16 was the best single parameter for discriminating an FFR ≤0.80 with 83.3% sensitivity and 67.9% specificity. The area under the curve (AUC) of V_sub/MLA² >4.16 (0.80 [95% confidence interval: 0.75 to 0.85]) was better than that of MLA (change in [Δ]AUC: 0.069; p < 0.001), %APV (ΔAUC: 0.096; p = 0.017), and diameter stenosis of QCA (ΔAUC: 0.080; p = 0.037) and was comparable to that of CT-FFR (AUC 0.77; ΔAUC: 0.035; p = 0.304).

Conclusions: V_sub is an independent determinant of an FFR ≤0.80. The mathematical index of V_sub/MLA² >4.16 assessed by coronary CTA shows better diagnostic performance for the detection of ischemia-producing lesions than CT-derived MLA alone or %APV and QCA parameters and was comparable to that of on-site CT-FFR.

Keywords: CT-FFR; coronary computed tomography angiography; fractional flow reserve; subtended myocardial mass.