Residual quantitative flow ratio to estimate post-intervention fractional flow reserve

Abstract

Abstract Objective To assess the performance of residual quantitative flow ratio (QFR) to estimate post percutaneous coronary intervention (PCI) fractional flow reserve (FFR). Background QFR computes FFR based on invasive coronary angiography (ICA) images. Residual QFR is a novel tool that assesses the functional outcome of an intervention by estimating post-PCI FFR. Methods Residual QFR analyses, using pre-PCI ICA images, were attempted in 159 vessels with post-PCI FFR measurements. QFR lesion location was matched with the treated segment to allow virtual removal of the lesion similar to the performed PCI and computation of residual QFR (Picture 1: case example of residual QFR analysis). A post-PCI FFR <0.90 was used to define a suboptimal PCI result. Results Residual QFR computation was successful in 128 (81%) vessels. Median residual QFR was higher than post-PCI FFR (0.96 interquartile range (IQR): 0.91–0.99 vs. 0.91 IQR: 0.86–0.96, p<0.001). A moderate correlation and agreement was observed between residual QFR and post-PCI FFR (Spearman correlation coefficient=0.56 and Intraclass correlation coefficient=0.47, p<0.001 for both). Following PCI, an FFR <0.90 was observed in 54 (42%) vessels. Specificity, positive predictive value, sensitivity, and negative predictive value of residual QFR for determining a suboptimal PCI result were 96% (95% confidence interval (CI): 87–99%), 89% (95% CI: 72–96%), 44% (95% CI: 31–59%), and 70% (95% CI: 65–75%), respectively. Overall, residual QFR had an accuracy of 74% (95% CI: 66–82%) and an area under the receiver operating characteristic curve of 0.79 for assessing a post PCI FFR <0.90. Conclusion A moderate correlation and agreement between residual QFR and post-PCI FFR was observed. Residual QFR ≥0.90 does not necessarily commensurate with an optimal PCI result. However, residual QFR <0.90 is a good indicator of a post-PCI FFR <0.90 and might therefore be utilized to determine PCI location in order to obtain a satisfactory PCI result (Picture 2: central illustration). Funding Acknowledgement Type of funding sources: None. Case example of residual QFR analysisCentral illustration