Quantitative Flow Ratio (QFR) has shown good diagnostic performance against Fractional Flow Reserve (FFR) in several meta-analyses, comparable or even superior to nonhyperemic pressure ratios. However, the reproducibility of QFR is modest and there is high inter- and intra-observer variability even when fairly experienced but non-core lab operators (at least 150 QFR procedure experience) are performing the analysis. Although smaller studies have demonstrated that non-core analysis and even paramedical user analysis can have good correlation with FFR, the concern about the diagnostic performance of QFR in real-world clinical practice by inexperienced users remains.

The primary objective of "Dedinje FFR/QFR Registry" is to determine the feasibility and diagnostic performance of QFR analysis by vendor-certified inexperienced medical users in a real-world setting using FFR as the gold standard. All patients >18 years old who present to the Institute for Cardiovascular Diseases "Dedinje" and undergo a planned or ad hoc FFR procedure will be asked to participate in the registry. FFR procedure is performed according to the standardized institutional protocol. QFR analysis will be subsequently performed offline according to a standard operating procedure.

Inclusion Criteria:

• >18 years old
• Had a clinically indicated FFR procedure performed (either as a planned procedure or ad hoc)

Exclusion Criteria:

• Declines to participate in the registry and provide informed consent

All patients >18 years old who present to the Institute for Cardiovascular Diseases "Dedinje" and undergo a planned or ad hoc FFR procedure will be asked to participate in the registry.

IPD contains sensitive identifying patient information that patients are told will not be shared with anyone outside of the primary team of researchers.