Quantitative Flow Ratio to Predict Non-Target-Vessel Events Prior to Planned Staged PCI in ACS Patients

Background: The optimal timepoint of staged percutaneous coronary intervention (sPCI) among patients with acute coronary syndrome (ACS) and multivessel disease (MVD) remains a matter of debate. Quantitative Flow Ratio (QFR) is a novel non-invasive method to assess the hemodynamic significance of coronary stenoses. We aimed to investigate whether QFR could optimize the timing of sPCI of non-target-vessels (non-TV) among ACS patients with MVD. Methods: For this cohort study, ACS patients discharged from Bern University Hospital, Switzerland, were eligible if non-TV sPCI was scheduled within 6 months after index PCI. The primary endpoint was non-TV myocardial infarction (MI) and urgent unplanned non-TV PCI before planned sPCI. The association between lowest QFR per patient measured in non-TV (from index angiogram) and the primary endpoint was assessed using a multivariable adjusted Cox proportional hazards regression with QFR included as linear and penalized spline (non-linear) terms. Results: QFR was measured in 1093/1432 ACS patients scheduled to undergo non-TV sPCI. Median time to sPCI was 28 days. The primary endpoint occurred in 5% of the patients. In multivariable analysis (1018 patients), there was no independent association between non-TV QFR and the primary endpoint (HR 0.87, 95% CI 0.69-1.05 [per 0.1 increase], p=0.125; non-linear p=0.648). Conclusions: In ACS patients scheduled to undergo sPCI at a median of 4 weeks after index PCI, QFR did not emerge as independent predictor of non-TV events prior to planned sPCI. Thus, this study does not provide conceptual evidence, that QFR is helpful to optimize the timing of sPCI.