Quantitative Flow Ratio Is Related to Intraluminal Coronary Stenosis Parameters as Assessed with Optical Coherence Tomography

Background: Quantitative flow ratio (QFR) is a novel method for assessing hemodynamic relevance of a coronary lesion based on angiographic projections without the need of a pressure wire. Various studies demonstrated that QFR consistently related to fractional flow reserve (FFR); however, it is still unclear to what extent QFR reflects intraluminal stenosis parameters. Given that optical coherence tomography (OCT) is currently the gold standard to assess intraluminal stenosis parameters, we investigated the relationship between OCT-derived lesion geometry and QFR. Methods: We determined QFR in 97 lesions from 87 patients who underwent coronary angiography and OCT due to stable angina. QFR was measured with proprietary software and compared with OCT-based assessment of intraluminal stenosis parameters as well as lesion morphology. Results: Mean QFR was 0.79 ± 0.10. QFR demonstrated a consistent association with FFR (r = 0.834, p < 0.001). Interestingly, QFR was associated with OCT-derived parameters such as minimal lumen area (MLA, r = 0.390, p = 0.015), percent area stenosis (r = 0.412, p < 0.001), minimal lumen diameter (MLD, r = 0.395, p < 0.001), and percent diameter stenosis (r = 0.400, p < 0.001). Both minimal luminal area (ROC = 0.734, optimal cut-off 1.75 mm(2)) and minimal luminal diameter (ROC = 0.714, optimal cut-off 1.59 mm) presented a good diagnostic accuracy in diagnosing hemodynamic relevance (QFR ≤ 0.80). There was no significant association between QFR and anatomic features of plaque vulnerability. Conclusion: OCT-derived intraluminal stenosis parameters are related to QFR values and predict hemodynamic lesion relevance. The data supports the validity of QFR as 3D-vessel reconstruction method to assess coronary physiology without the need of a pressure wire.