Diagnostic Performance and Prognostic Ability of the QFR

The quantitative flow ratio (QFR) is a novel angiography-based tool used to assess functional ischemia caused by coronary stenosis. Computation of the fractional flow reserve (FFR) from coronary angiography is based on 3D reconstruction and fluid dynamics algorithms using a modified frame count; therefore, we do not need to induce hyperemia or perform invasive procedures with a pressure wire to measure it. During the past few years, the diagnostic accuracy of the QFR was investigated and showed favorable outcomes. However, data for patients with acute coronary syndrome are lacking. In addition, no data are available for the performance of the QFR in predicting clinical outcomes. We aim to evaluate the diagnostic performance of the QFR versus the FFR and their predictive abilities for clinical outcome in a real-world all-comer population.

The Catholic imaging and Functional Research (C-iFR) Cohort was designed to evaluate the diagnostic performance and clinical outcome predictive ability of the QFR in consecutive patients undergoing CAG and the FFR at 4 major cardiac centers in Korea from January 2012 to May 2018. All hospitals (Seoul St. Mary's Hospital, Seoul; St. Paul's Hospital, Seoul; Incheon St. Mary's Hospital, Incheon; Uijeongbu St. Mary's Hospital, Uijeongbu) perform a high volume of percutaneous coronary intervention (PCI) procedures, with more than 800 PCI procedures performed per year. This QFR registry includes demographic characteristics, clinical information, laboratory data, QFR findings, and FFR findings, with clinical outcome data collected over 4 years (a median of 2 years)

Inclusion criteria

• subject ≥18 years
• Patients suspected with ischemic heart disease
• All-comer patients with SA, UA and AMI whose CAG results showed intermediate stenosis (50-70%) indicative of physiologic lesions
• Patients whose target vessels were able to analyze QFR

Exclusion criteria

Patients with insufficient CAG data due to reasons below

• CAG data uploading error
• 2 projection angles <25 degrees apart
• only 1 projection angle image exists
• images with suboptimal contrast filling
• images with too much panning or too much magnification
• containing an ostial lesion of the left main coronary artery or right coronary artery
• anatomical vessel problems including severe overlap, severe tortuosity, foreshortening, diffuse lesions, additional far distal lesion