Angiography-derived QFR and RWS predict in-stent restenosis after PCI: a retrospective cohort study

Background Quantitative flow ratio (QFR) is an emerging angiography-based tool for functional lesion assessment, while radial wall strain (RWS) represents a novel angiography-derived method to evaluate the biomechanical property of coronary arteries. However, the predictive utility of QFR and RWS in assessing the risk of in-stent restenosis (ISR) is unclear. Objective To investigate the predictive value of quantitative flow ratio (QFR) and radial wall strain (RWS) in assessing the risk of in-stent restenosis (ISR). Methods This retrospective study enrolled 236 patients who underwent percutaneous coronary intervention (PCI) at a single center between October 2016 and January 2025. Pre-stent and Post-stent QFR measurements (QFR, ΔQFR, ΔQFR/stent length (mm), maximum percentage diameter stenosis (Max %DS), etc.), L-index (residual QFR /residual length (coronary length - stent length)), R-stenosis (post-stent Max %DS / pre-stent Max %DS), post-stent RWS measurements (RWS, RWS%) both at baseline were recorded. Patients with ISR defined as ≥50% diameter stenosis (DS) within the stent, or within 5 mm from the stent edges, luminal narrowing as judged visually were considered for the study. Results Follow-up angiography was performed in all patients with a duration of 2.9–78.9 (mean 19.4 ± 10.8) months. Follow-up angiography revealed in-stent restenosis (≥50% diameter stenosis) in 106 patients (44.9%). Lasso regression identified post-stent Max %DS, L-index, RWS% and R-stenosis as candidate variables. In multinomial logistics regression, Max %DS (OR 1.067, 95% CI 1.001–1.137), L-index (OR 9.872e163, 95% CI 9.330e49–1.045e278), RWS% (OR1.115, 95% CI 1.061–1.172) were significant (P < 0.05) independent risk factors for in-stent restenosis≥ 50%. ROC analysis showed AUC was 0.781 (95% CI, 0.723–0.839) and cutoff was 0.214 at Max %DS, AUC was 0.647 (95% CI, 0.575–0.719) and cutoff was 0.001336 at L-index, AUC was 0.750 (95% CI, 0.688–0.811) and cutoff was 0.16 at RWS%. Conclusions Angiography-derived QFR and RWS is feasible in patients following stents implantation and shows prognostic value in predicting in-stent restenosis after stents implantation, and Max %DS, L-index and RWS% are significant risk factors for in-stent restenosis.