The diagnostic value of a hybrid quantitative flow ratio–FFR strategy for ischemia-causing stenosis in patients with unstable angina and its impact on revascularization strategy

Abstract Quantitative flow fraction (QFR) is a functional test without a guide wire based on coronary angiography. In this study, flow reserve fraction (FFR) was used as the reference standard to verify the diagnostic value of QFR in patients with unstable angina pectoris with critical coronary artery disease (coronary artery stenosis degree of 40%-70%) functional stenosis, and to evaluate the effect of fusion strategies of QFR-FFR on revascularization strategies in such patients.This retrospective study included patients with unstable angina pectoris who were admitted to Fuwai Central China Cardiovascular Hospital from June 1, 2018 to June 1, 2023 and underwent coronary flow reserve fraction examination. QFR values of target vessels were analyzed offline by AngioPlus (Shanghai Pulsation Medical Imaging Technology Co., LTD.), the second-generation QFR detector, and anatomical parameters of the diseased vessels were recorded as follows: minimal luminal diameter (MLD), percent diameter stenosis (DS%), minimal luminal area (MLA), percent area stenosis (AS%). Functional coronary artery stenosis is defined as FFR≤0.80. Using FFR as the gold standard, the AUC values of contrast-flow QFR (cQFR) and fixed-flow QFR (fQFR) for identifying functional coronary artery stenosis in patients with unstable angina pectoris were 0.832（95%CI：0.772~0.892，P=0.000）and 0.817（95%CI：0.756~0.877，P=0.000）, respectively. The diagnostic accuracy, sensitivity and specificity of cQFR and fQFR were 85.52%、78.57%、89.78% and 79.19%、75.00%、81.75%, respectively. Delong test showed that there was no significant difference between cQFR and fQFR in the diagnostic value of functional stenosis in patients with unstable angina. When in the QFR "gray zone" (0.77 to 0.87), compared with fQFR, cQFR had a higher AUC for diagnosing coronary critical lesion functional stenosis in patients with unstable angina pectoris (0.881 vs 0.705). Furthermore, a fusion strategy using cQFR-FFR avoided invasive FFR measurements in 71.49% of patients. With FFR as the gold standard, QFR has a certain diagnostic value for coronary artery critical lesion functional stenosis in patients with unstable angina pectoris. When QFR is in the "gray area", the diagnostic value of cQFR is higher. At this time, the fusion strategy of cQFR-FFR can avoid FFR measurement in some patients.