Coronary Stenosis: Morphologic Index Characterized by Using CT Angiography Correlates with Fractional Flow Reserve and Is Associated with Hemodynamic Status

Abstract

Purpose To study the diagnostic performance of the ratio of lesion length (LL) to the fourth power of minimal lumen diameter (MLD) (MLD4) at coronary computed tomographic (CT) angiography for differentiating between hemodynamically significant and nonsignificant lesions, with correlation with fractional flow reserve (FFR). Materials and Methods This retrospective study had institutional review board approval, and the need to obtain informed consent was waived. Sixty-one patients (mean age, 65.3 years ± 8.8 [standard deviation]; range, 43–82 years; 43 men and 18 women; P = .019 for age) who underwent both coronary CT angiography and FFR measurement at conventional coronary angiography within 2 weeks were retrospectively included in this study. LL/MLD4 ratio, along with other parameters, including minimal luminal area (MLA), stenosis diameter, stenosis area, plaque burden, remodeling index, and Agatston score of lesions, were recorded. Lesions with FFRs of less than 0.8 were considered to be functionally significant. Univariate and multivariate statistical tests were performed to identify variables associated with hemodynamically significant lesions. Results Sixty-one patients with 85 lesions were ultimately included for analysis. LL, stenosis diameter, stenosis area, and plaque burden were longer or larger in the group with FFRs of less than 0.8 (P < .001 for all), while smaller MLA and MLD were also noted (P < .001). Mean LL/MLD4 ratio was significantly larger in the group with FFRs of less than 0.8 than in the group with FFRs of 0.8 or greater (9.7 ± 7.5 vs 3.1 ± 3.6, P < .001). Rest myocardial perfusion defect was recorded in five lesions with FFRs of less than 0.8 (P = .006). LL/MLD4 ratio proved at multivariate analysis to be the only independent predictor of hemodynamically significant stenosis (odds ratio = 1.44; P = .043). When 3.86 was used as the cutoff value for LL/MLD4 ratio, the sensitivity and specificity for diagnosing hemodynamically significant lesions were 82.9% (29 of 35) and 82% (41 of 50), respectively. Conclusion The LL/MLD4 ratio, as characterized by using coronary CT angiography, correlates inversely with FFR measurements and is associated with the hemodynamic status of coronary stenoses. © RSNA, 2013 Online supplemental material is available for this article.