P2701Comparison of myocardial ischemia assessed by contrast-flow quantitative flow ratio (cQFR) and by stress MRI in patients with stable coronary artery disease

Abstract

Abstract Background Contrast-flow quantitative flow ratio (cQFR) is a new technology for evaluation of coronary stenosis. cQFR allows to derive the fractional flow reserve (FFR) from coronary angiograms. Based on a three dimensional coronary model, FFR is calculated from computational fluid dynamics. Head to head comparisons with FFR showed an overall diagnostic accuracy of 85%. cQFR does not require coronary wires or hyperemia. However, the ability of cQFR to detect myocardial ischemia is unknown. Therefore, the aim of this study was to evaluate the relationship between cQFR and myocardial ischemia assessed by stress magnetic resonance imaging (stress MRI). Methods cQFR analysis was performed in patients selected from the hospital database who received stress MRI and coronary angiography. A relevant ischemia on stressMRI was defined as a perfusion deficit in ≥2 of 16 segments. The cQFR was based on 3-dimensional quantitative coronary angiography (3D-QCA) using the QAngio XA 3D 1.1, Medis Medical Imaging System, Leiden, The Netherlands. Two blinded investigators analysed all 3 main coronary vessels of each patient measuring diameter stenosis (DS), area stenosis (AS) and cQFR. A cQFR of ≤0.8 was considered abnormal. The primary endpoint was sensitivity and specificity of cQFR using stress MRI as a reference standard. Results 125 vessels of 53 patients could be fully analysed by cQFR (78.6%). The sensitivity of cQFR in detecting significant epicardial stenoses of coronary vessels with documented ischemia in stress MRI was 75%, the specificity was 87%. The 3D-QCA-derived diameter stenoses and area stenoses in vessels with positive stress MRI were significantly higher than in vessels without ischemia (see Table 1). Table 1. Means of diameter stenosis (DS) und area stenosis (AS) with interquartile range (IQR) Total (n=125) Ischemia (n=32) No Ischemia (n=93) p-value DS [%] 42.3 (28.3–53.1) 57.1 (47–68.5) 37.7 (27.6–45.1) <0.0001 AS [%] 51.8 (32.4–69.7) 68.9 (56.8–85.9) 46.5 (29.7–62.7) <0.0001 Conclusion The analysis reveals a high correlation between relevant coronary stenosis measured by cQFR and ischemic areas detected by stress MRI. Differences between the two methods are plausible because stress MRI detects ischemia due to other reasons than epicardial stenosis. Further randomized studies are mandatory to verify the prognostic significance of the cQFR measurements.