Lesion Length Improves Diagnostic Accuracy of Intravascular Ultrasound for Detecting Functional Intermediate Coronary Stenosis Evaluated With Coronary Angiography-Derived Fractional Flow Reserve in Non-left Main Artery

Objective: Intravascular ultrasound (IVUS) parameters, for example, minimal lumen area (MLA) and area stenosis (AS), poorly identified functional intermediate coronary stenosis (ICS). For detecting functional ICS defined by coronary angiography-derived fractional flow reserve (caFFR), our study aims to determine whether IVUS parameters integrated with lesion length (LL) by three-dimensional quantitative coronary analysis (3D-QCA) could improve diagnostic value. Methods: A total of 111 patients with 122 ICS lesions in the non-left main artery were enrolled. MLA and AS were calculated in all lesions by IVUS. Diameter stenosis (DS%) and LL were measured by 3D-QCA. caFFR was computed by the proprietary fluid dynamic algorithm, a caFFR <= 0.8 was considered as functional stenosis. Receiver-operating curve analyses were used to compare the diagnostic accuracy among indices to predict functional stenoses. Results: Mean caFFR values in all lesions were 0.86 +/- 0.09. Lesions with caFFR <= 0.8 showed lower MLA and higher AS (MLA: 3.3 +/- 0.8 vs. 4.1 +/- 1.2, P = 0.002; AS: 71.3 +/- 9.6% vs. 63.5 +/- 1.3%, P = 0.007). DS% and LL were more severe in lesions with caFFR <= 0.8 (DS%: 45.5 +/- 9.6% vs. 35.5 +/- 8.2%, P < 0.001; LL: 31.6 +/- 12.9 vs. 21.0 +/- 12.8, P < 0.001). caFFR were correlated with MLA, AS, and LL (MLA: r = 0.36, P < 0.001; AS: r = -0.36, P < 0.001; LL: r = -0.41, P < 0.001). Moreover, a multiple linear regression analysis demonstrated that MLA (beta = 0.218, P = 0.013), AS (beta = -0.197, P = 0.029), and LL (beta = -0.306, P > 0.001) contributed significantly to the variation in caFFR. The best cutoff value of MLA, AS, and LL for predicting caFFR <= 0.8 were 3.6 mm(2), 73%, and 26 mm, with area under the curve (AUC) of 0.714, 0.688, and 0.767, respectively. Combined with MLA, AS, and LL for identifying functional ICS, the accuracy was the highest among study methods (AUC: 0.845, P < 0.001), and was significantly higher than each single method (All P < 0.05). Conclusion: Lesion length can improve the diagnostic accuracy of IVUS-derived parameters for detecting functional ICS.