Quantitative flow ratio and fractional flow reserve mismatch – clinical and biochemical predictors of measurement discrepancy

Introduction
Fractional flow reserve (FFR) is the gold standard for functional assessment of intermediate lesions. However, assessing a stenosis with pressure wire prolongs the procedure, increases costs and carries a risk of procedure-related adverse events. Quantitative flow ratio (QFR) is a wire-free method for detection of significant ischemia based on 3D reconstruction of angiographic images and TIMI frame count.

Aim
To evaluate the influence of laboratory and clinical variables on QFR-FFR mismatch.

Material and methods
We retrospectively computed QFR (Medis Suite XA/QAngio XA 3D/QFR, Medis/Netherlands) in suitable cases with corresponding FFR (PressureWire, Abbott, US). Uni-/multivariate analysis was performed to identify clinical and biochemical predictors of QFR-FFR mismatch.

Results
Two hundred six lesions (196 patients, 76% male, mean age: 66.4 ±10.1 years) were included. Chronic kidney disease (CKD) and insulin-treated diabetes mellitus (ITDM) were associated with significantly larger differences between QFR and FFR values (–0.062 ±0.031 vs. –0.025 ±0.068; p = 0.027 and –0.059 ±0.07 vs. –0.027 ±0.074; p = 0.039; respectively). CKD was associated with a decrease of diagnostic efficiency (AUC = 0.67, 95% CI: 0.46–0.88 vs. AUC = 0.89, 95% CI: 0.84–0.94, p = 0.05). For biochemical variables only weak Spearman correlations were identified for hemoglobin concentration (r = –0.18) and hematocrit levels (r = –0.18).

Conclusions
CKD may impair the QFR diagnostic accuracy. Larger, prospective studies are needed to further explore this potential relationship.