To compare the clinical outcomes of fractional flow reserve (FFR)-guided strategy versus intravascular ultrasound (IVUS)-guided stent implantation after angiography-derived FFR-based decision-making.

1. Hypothesis: The IVUS-guided stent implantation after angiography-derived FFR-based decision-making will show superiority in terms of a lower rate of patients-oriented composite outcomes (POCO) at 24 months after randomization compared with the FFR-guided PCI strategy in patients with coronary stenosis.

2. Research materials and indication for revascularization:

   2.1 Experimental group: PCI will be performed if angiography-derived FFR ≤0.80 and will be deferred if angiography-derived FFR >0.80; If PCI is performed, PCI optimization using IVUS will be performed following the recommended criteria: ① Plaque burden at stent edge ≤55%; ② Minimal stent area ≥ 5.5 mm2, or minimal stent area ≥ distal reference lumen area.

   2.2 Control group: PCI will be performed if FFR ≤0.80 and will be deferred if FFR >0.80; If PCI is performed, PCI optimization using FFR will be performed following the recommended criteria: ① Post-PCI FFR ≥ 0.88, or ② Post-PCI ΔFFR ([FFR at stent distal edge] - [FFR at stent proximal edge]) < 0.05.

3. Sample size: In the post-hoc analysis of the FLAVOUR I study applying QFR analysis, the 2-year POCO rate was 13.0% in the PCI group with FFR ≤0.80 and undergoing FFR-based PCI optimization and 7.1% in the PCI group with QFR ≤0.80 and undergoing IVUS-based PCI optimization. Meanwhile, the 2-year POCO rate was 5.8% and 6.5% in the deferral of PCI group with FFR >0.80 and QFR >0.80, respectively. Assuming a PCI rate of 70% in patients with coronary artery lesions with 50-90% stenosis that is the inclusion criteria for the current study, and considering event rates from historical studies evaluating FFR- and QFR-guided PCI strategies, the cumulative incidence rate of POCO at 24 months was estimated to be 13.0% in the control group (FFR group) and 9.0% in the experimental group (QFR-IVUS group).

   • Primary endpoint: POCO, defined as a composite of death from any cause, MI, or any revascularization at 24 months after randomization.
   • Design: superiority
   • Sampling ratio: experimental group : control group = 1:1
   • Type I error (α): One-sided 2.5%
   • Accrual time: 24 months
   • Total time: 4 years (accrual 24 months + follow-up 24 months)
   • Assumption: POCO 13.0% vs. 9.0% in control or experimental group, respectively
   • Statistical power (1- β): 90%
   • Primary statistical method: Kaplan-Meier survival analysis with log-rank test
   • Estimated attrition rate: total 10%
   • Stratification in randomization: Presence of diabetes mellitus

Based on the above assumption, we would need total 1,942 patients (971 patients in each group) with consideration of an attrition rate.

Inclusion Criteria:

• Subject must be ≥ 19 years.
• Subject is able to verbally confirm understanding of risks, benefits and treatment alternatives of receiving invasive physiologic or imaging evaluation and PCI with a drug-eluting stent (DES) and he/she or his/her legally authorized representative provides written informed consent.
• Subjects suspected with ischemic heart disease.
• Subjects with coronary artery diameter stenosis 50-90% by angiography-based visual estimation eligible for stent implantation.
• Target vessel size ≥ 2.5mm in visual estimation.

Exclusion Criteria:

• Known hypersensitivity or contraindication to any of the following medications: Heparin, Aspirin, Clopidogrel, Prasugrel, Ticagrelor
• Active pathologic bleeding.
• Gastrointestinal or genitourinary major bleeding within the prior 3 months.
• History of bleeding diathesis, known coagulopathy.
• Non-cardiac co-morbid conditions with life expectancy < 2 years.
• Target lesion located in coronary arterial bypass graft.
• Left main coronary artery stenosis ≥ 50%.
• Chronic total occlusion in the study target vessel.
• Culprit lesion of ST-elevation myocardial infarction (STEMI).
• Not eligible for angiography-derived FFR (ostial RCA ≥ 50% stenosis, severe tortuosity, severe overlap, poor image quality).

The deidentified data will be shared after publication of first manuscript

Data will be available within 12 months of study completion.

Data access requests will be reviewed by an external Independent Review Panel. Requestors will be required to sign a Data Access Agreement