Objectives: The aim of this study was to investigate the prognostic role of quantitative flow ratio (QFR) measured immediately after successful percutaneous coronary intervention (PCI) of chronic total occlusion (CTO) lesions.

Background: Prognostic value of post-PCI QFR in non-CTO lesions was reported in previous studies. However, data about prognostic implication of QFR post-CTO PCI is lacking. 

Methods: All patients who underwent a PCI of coronary CTO in our center from October 2017 to December 2020 were screened. Patients with successful CTO-PCI and suitable angiographic views for QFR analysis at the end of the procedure were included in our analysis. We divided the patients in to two groups according to a previously reported cut-off value of post-PCI QFR; group with QFR ≥ 0.89 (n= 272) and group with low QFR < 0.89 (n=52).  The primary endpoint of this study was target-vessel failure (TVF) at 2-year. TVF was defined as the composite of cardiac death, target-vessel myocardial infarction (MI) and target-vessel revascularization (TVR).

Results: Among 470 CTO lesions performed during the study period, 324 were eligible for QFR analysis (unsuccessful CTO-PCIs= 65 (13.8%), unsuitable angiographic angulations for QFR analysis= 81 (17.2%)). Mean age of our population was 68.6 ± 10.6 years. 76.5% of patients had J-CTO score ≥ 2 and mean target-vessel SYNTAX score was 12.75 ± 4.7. The mean QFR value post-CTO PCI was 0.94 ± 0.06. A total of 46 (14.2%) TVF occurred at 2-year. Patients with low post-CTO QFR < 0.89 (n=52) did not show more TVF compared with those with high post-CTO QFR ≥ 0.89 (n= 272), (21.6% vs. 13.2%, log rank, p=0.184). QFR also failed to predict 2-year TVF at univariate level analysis (unadjusted HR 1.58; 95% CI 0.80–3.10, p=0.189), while target-vessel SYNTAX score was the only independent predictor of 2-year TVF (aHR 1.07; 95% CI: 1.02 – 1.12, p=0.009). The diagnostic performance of target-vessel SYNTAX score to predict 2-year TVF was moderate by using receiver operating characteristics curve (ROC; Area under the curve 61%, CI 95% 0.53 – 0.68, p=0.01), with the optimal cut-off value 11.5 (sensitivity 0.643, specificity 0.557). 

Conclusion: QFR measured immediately after successful CTO-PCI could not predict TVF within two years. However, pre-procedure target-vessel SYNTAX score was an independent predictor for 2-year TVF. These findings confirm the limited utility of physiological assessment immediately after successful CTO-PCI, in contrast to pre-procedural anatomic characteristics.