Grey-zone–dependent discordance between angiography-based quantitative flow ratio and fractional flow reserve: interaction with lesion length in an expanded real-world Cohort
E Sideras Chantant Marakas, D Lempidakis, A Papoutsakis, S Petousis, E Zacharis, A Progiou, N Poulidakis, M Smaragdaki, P Rogdakis, D Andrianis, G Kochiadakis, E Simantirakis, E Skalidis, M HamilosAbstract
Background
Fractional flow reserve (FFR) remains the reference standard for invasive physiologic lesion assessment. Quantitative flow ratio (QFR) provides a wire-free alternative; however, determinants of clinically relevant discordance remain incompletely defined.
Purpose
To evaluate agreement between QFR and FFR and determine whether lesion length and grey-zone physiology interact to influence discordance.
Methods
Seventy-six lesions with available FFR measurements were included in the comparative analysis. Hemodynamic significance was defined as FFR ≤0.80 and QFR ≤0.80. Correlation and categorical agreement were calculated. Discordance was modeled using penalized logistic regression lesion length (per 10 mm), FFR grey-zone status (0.75–0.85), and their interaction.
Results
QFR correlated with FFR (r=0.57, p= 0.000000094) with 82.9% agreement (κ=0.61). Overall discordance occurred in 17.1% of lesions. Grey-zone lesions demonstrated substantially higher discordance rates. In penalized logistic regression (n=73), grey-zone status was associated with a 4.5-fold higher odds of QFR–FFR discordance (OR 4.50). An interaction between lesion length and grey-zone status was observed, with increasing lesion length amplifying discordance specifically in borderline lesions (interaction OR 1.18 per 10 mm).
Conclusions
In an expanded real-world cohort, QFR shows moderate agreement with FFR; however, physiologic discordance is strongly influenced by borderline FFR values. Lesion length amplifies discordance predominantly within the grey zone, suggesting that anatomic complexity modulates angiography-based physiologic assessment in intermediate lesions.