Diagnostic accuracy of automatic quantitative flow ratio for hemodynamic assessment of coronary artery stenosis: prospective observational study

Abstract Background Quantitative flow ratio (QFR) is a method for evaluating fractional flow reserve (FFR) without the use of an invasive coronary pressure wire or pharmacological hyperemic agent. Automatic QFR (auto QFR) is a recently developed, simpler method of calculating QFR that uses a patient-specific TIMI (Thrombolysis in Myocardial Infarction) frame count, but with automatically specified start and end frames. Although the previous studies demonstrated that contrast QFR is more accurate than fixed QFR, there is no evidence for auto QFR. Purpose The aim of this study was to evaluate the diagnostic performance of auto QFR, fixed QFR, and contrast QFR for the diagnosis of hemodynamically significant coronary stenosis defined by FFR ≤0.80. Methods This prospective, multicentre trial enrolled patients suspected with coronary artery disease undergoing diagnostic coronary angiography with an indication for to perform invasive FFR. QFR was calculated at a blinded core laboratory. The primary endpoint was the diagnostic accuracy of auto QFR, fixed QFR, and contrast QFR to determine hemodynamically significant coronary stenosis using invasive FFR (≤0.80) as a reference standard. Results A total of 325 vessels from 274 patients were analysed. Mean FFR was 0.82±0.09, mean auto QFR was 0.80±0.12, and mean contrast QFR was 0.82±0.11, respectively. The overall diagnostic accuracy for identifying an FFR of ≤0.80 was highest by contrast QFR (81.5%), followed by fixed QFR (79.1%), and auto QFR (77.5%). The AUC was higher for contrast QFR (AUC 0.885; 95% CI: 0.845-0.925) than fixed QFR (AUC 0.856; 95% CI: 0.812-0.900) or auto QFR (AUC 0.854; 95% CI: 0.806-0.901), but did not differ significantly between fixed QFR and auto QFR (Figure). Conclusions There was no significant difference in AUC between fixed and auto QFR, but the accuracy of contrast QFR was significantly higher compared to both QFRs. Auto QFR has the advantage of faster computation time while using patient-specific coronary flow, but accuracy still needs to be improved.