Validity and correlation of quantitative flow ratio with fractional flow reserve for assessment of intermediate coronary lesions.

Background: The angiographic percent diameter stenosis (%DS) do not assess the physiological significance of epicardial coronary stenosis. The currently practised physiological indices require pressure wires with or without adenosine-induced hyperaemia. Quantitative flow ratio (QFR) is an angiography-based method to determine the functional significance of coronary stenosis. The present study aimed to analyse the diagnostic performance of QFR in comparison to fractional flow reserve (FFR) in intermediate coronary lesions.
Materials and Methods: It was a single centre retrospective study to analyse the diagnostic performance of offline QFR with the previously performed FFR in the last six years. A total of 56 interrogated vessels were included for the analysis. Offline QFR analysis was performed and correlated with FFR values in the intermediate coronary stenoses.
Results: The mean age of the study population was 62.4 ± 9.1 years, including 81% men. The left anterior descending artery (50%) was the most common analysed vessel followed by left circumflex (27%) and right coronary (21%) arteries. The mean % DS and % area stenosis were 45.25 ± 11.22% and 57.45% ± 16.25%, respectively. The mean FFR and QFR values were 0.83 ± 0.06 and 0.82 ± 0.10, respectively. A strong positive correlation was found between FFR and QFR with a Spearman correlation coefficient of 0.56. Receiver operating curve analysis for QFR and %DS with a FFR cut off value <0.80 showed an area under the curve of 0.97 and 0.77, respectively. The sensitivity, specificity and diagnostic accuracy of QFR were 87.5%, 95% and 92.8%, respectively. There was a discordance in four vessels (7.1%) between QFR and FFR.
Conclusion: QFR has a good diagnostic performance in comparison to the gold standard FFR for physiological assessment of intermediate lesions. Its performance is significantly better than the anatomical % DS ( p  < 0.001).