Quantitative Flow Ratio (QFR) is a novel method for evaluating the functional significance of coronary stenosis. The purpose of the FAVOR II China study is to evaluate the diagnostic accuracy of on-line QFR with FFR as the reference standard. The secondary purpose is to compare the diagnostic accuracies between online QFR and online QCA, with FFR as the reference standard.

Patients at high risk of having one or more coronary stenosis are evaluated routinely by invasive coronary angiography. Lesions are often quantified by QCA, but fractional flow reserve is increasingly used to assess functional significance of identified stenosis. FFR is assessed during CAG by advancing a wire with a pressure transducer towards the stenosis and measure the ratio in pressure between the two sides of the stenosis during medical induced maximum blood flow (hyperemia).

The solid evidence for FFR evaluation of coronary stenosis and the relative simplicity in performing the measurements have supported adoption of an FFR based strategy in many centers but the need for interrogating the stenosis by a pressure wire, the cost of the wire, and the drug inducing hyperemia limits more widespread adoption.

QFR is a novel method for evaluating the functional significance of coronary stenosis by calculation of the pressure drop in the vessel based on two angiographic projections. The FAVOR Pilot study (Tu et al.) showed promising results for core laboratory QFR analysis in selected patients. However, the accuracy of QFR when assessed online in the catheterization laboratory is unknown. The purpose of the FAVOR II China study is to evaluate the diagnostic accuracy of on-line QFR with FFR as the reference standard. The secondary purpose is to compare the diagnostic accuracies between online QFR and online QCA, with FFR as the reference standard. It is a prospective and multi-center trial with a total of 308 patients conducted at 5 Chinese centers.

Inclusion Criteria:

General Criteria:

• Stable and unstable angina pectoris or secondary evaluation of stenosis after acute MI
• Age > 18 years
• Able to provide signed informed consent

Angiographic inclusion criteria:

• At least one stenosis with diameter stenosis of 30%-90% by visual estimate
• Reference vessel size > 2 mm in stenotic segment by visual estimate

Exclusion Criteria:

General Criteria:

• Ineligible for diagnostic intervention or FFR examination
• Myocardial infarction within 72 hours
• Severe heart failure (NYHA≥III)
• S-creatinine>150µmol/L or GFR<45 ml/kg/1.73m2
• Allergy to contrast agent or adenosine
• Factors that might substantially impact the angiographic image quality, e.g, frequent atrial premature beat or atrial fibrillation

Angiographic exclusion criteria:

• The interrogated stenosis is caused by myocardial bridge
• Ostial lesions less than 3 mm to the aorta
• Side branches of the bifurcation lesions with Median Classification of 111 or 101
• Poor angiographic image quality precluding contour detection
• Severe overlap of stenotic segments
• Severe tortuosity of target vessel

Patients with coronary artery disease admitted for coronary angiography due to high risk of significant coronary stenosis