Feasibility and prognostic role of machine learning-based FFR in patients with stent implantation.

Objectives: To investigate the feasibility and prognostic implications of coronary CT angiography (CCTA) derived fractional flow reserve (FFR) in patients who have undergone stents implantation.

Methods: Firstly, the feasibility of FFR in stented vessels was validated. The diagnostic performance of FFR in identifying hemodynamically in-stent restenosis (ISR) in 33 patients with invasive FFR ≤ 0.88 as reference standard, intra-group correlation coefficient (ICC) between FFR and FFR was calculated. Secondly, prognostic value was assessed with 115 patients with serial CCTA scans after PCI. Stent characteristics (location, diameter, length, etc.), CCTA measurements (minimum lumen diameter [MLD], minimum lumen area [MLA], ISR), and FFR measurements (FFR, ΔFFR, ΔFFR/stent length) both at baseline and follow-up were recorded. Longitudinal analysis included changes of MLD, MLA, ISR, and FFR. The primary endpoint was major adverse cardiovascular events (MACE).

Results: Per-patient accuracy of FFR was 0.85 in identifying hemodynamically ISR. FFR had a good correlation with FFR (ICC = 0.84). 15.7% (18/115) developed MACE during 25 months since follow-up CCTA. Lasso regression identified age and follow-up ΔFFR/length as candidate variables. In the Cox proportional hazards model, age (hazard ratio [HR], 1.102 [95% CI, 1.032-1.177]; p = 0.004) and follow-up ΔFFR/length (HR, 1.014 [95% CI, 1.006-1.023]; p = 0.001) were independently associated with MACE (c-index = 0.856). Time-dependent ROC analysis showed AUC was 0.787 (95% CI, 0.594-0.980) at 25 months to predict adverse outcome. After bootstrap validation with 1000 resamplings, the bias-corrected c-index was 0.846.

Conclusions: Noninvasive ML-based FFR is feasible in patients following stents implantation and shows prognostic value in predicting adverse events after stents implantation in low-moderate risk patients.

Key Points: • Machine-learning-based FFR is feasible to evaluate the functional significance of in-stent restenosis in patients with stent implantation. • Follow-up △FFR along with the stent length might have prognostic implication in patients with stent implantation and low-to-moderate risk after 2 years follow-up. The prognostic role of FFR in patients with moderate-to-high or high risk needs to be further studied. • FFR might refine the clinical pathway of patients with stent implantation to invasive catheterization.