Department of Clinical Medicine

AIMS: To evaluate diagnostic accuracy of quantitative flow ratio (QFR). A novel method was used for non-invasive functional assessment of intermediate coronary lesions. Fractional flow reserve (FFR) is the gold standard for functional assessment of intermediate lesions. However, interrogating a stenosis with pressure wire prolongs the procedure, increases costs and carries a risk of procedure-related adverse events. QFR is a wire-free method for computation of FFR based on 3D reconstruction of angiographic images and modified TIMI frame count.

METHODS AND RESULTS: We retrospectively computed QFR (Medis Suite XA/QAngio XA 3D/QFR, Medis/Netherlands) in suitable cases with corresponding FFR (PressureWire™, Abbott, US/). Four QFR measures were tested against FFR: (1) fixed-flow QFR (fQFR), (2) vessel QFR (vQFR), (3) lesion QFR (lQFR) and (4) index QFR (iQFR). 857 lesions (740 patients) were reviewed, 306 (268 patients) met technical inclusion criteria for QFR (two optimal angiographic projections > 25° apart; no ostial location, no overlapping/shortening, frame-rate ≥ 15 fps). Mean angiographic percentage diameter stenosis was 51.3 ± 10.18%. Wire-based FFR ≤ 0.80 was found in 130 lesions (42.5%). Strong Pearson correlation was identified for iQFR (r = 0.85), fQFR (r = 0.73), vQFR (r = 0.78) and lQFR (r = 0.70). The optimal QFR decision values corresponding to FFR = 0.80 were iQFR = 0.79 (AUC = 0.94), fQFR = 0.73 (AUC = 0.87), vQFR = 0.77 (AUC = 0.90), and lQFR = 0.83 (AUC = 0.82). Sensitivity and specificity > 95% were identified for iQFR ≤ 0.74 (n = 89, 29%) and > 0.83 (n = 116, 38%), respectively.

CONCLUSIONS: The QFR value at the pressure transducer position (iQFR) was the best corresponding QFR model. iQFR is characterised by high diagnostic accuracy and used in a hybrid model with FFR which may reduce the number of procedures requiring pressure-wire by two-thirds.