INsTantenous wavE-Free Ratio-guided PCI Versus Fractional Flow REserve-Guided PCI in rouTine Clinical Practice, Prospective, Multicenter Registry

In this study, the investigators will validate the clinical relevance of instantaneous wave free ratio (iFR)-guided strategy in real world clinical practice in Korea. The 1,200 patients who underwent iFR measurement will be prospectively enrolled at 5 centers in Republic of Korea. In patients who were indicated revascularization after iFR measurement (iFR\<0.90), iFR pullback system (iFR Scout) and post-revascularization iFR measurement will be routinely performed. The primary hypothesis will be tested for non-inferiority of iFR-guided strategy, compared with FFR-guided strategy in terms of 2-year clinical outcomes. For the clinical outcome data following FFR-guided strategy will be used from the pooled data of the DEFER-DES trial, the 3V FFR FRIENDS registry (NCT01621438), and Korean 4-center FFR registry. Using those data, 1200 patients will be selected from the pooled data. In addition, routine application of iFR Scout and post-revascularization iFR measurement will enable us to validate the clinical relevance of iFR-based prediction of acute procedural results and to compare FFR-pullback methods. Primary Hypothesis: The iFR-guided strategy will be non-inferior regarding patient-oriented composite outcomes (a composite of any death, any MI, any revascularization) at 2-year, compared with FFR-guided strategy. Primary Outcome: 1\] Patient-oriented composite outcome (POCO), defined as a composite of any death, any myocardial infarction (MI) or any revascularization at 2-year after index procedure according to the ARC consensus \[2\] Difference between Predicted post-PCI iFR value from iFR Scout and Actual post-PCI iFR measurement Sample Size 1,200 patients with suspected ischemic heart disease including stable angina, or acute coronary syndrome including unstable angina, non ST-segment elevation MI, or ST-segment elevation MI with non-culprit stenosis enrolled at 5 centers in Republic of Korea. 1. Inclusion Criteria ① Subject must be ≥18 years ② Patients suspected with ischemic heart disease ③ Patients with coronary artery stenosis with intermediate degree of stenosis (40-70% stenosis by visual estimation) in major epicardial coronary artery amenable to stent implantation or vessel size≥2.5 mm without definitive previous evidence of myocardial ischemia. ④ Subject is able to verbally confirm understandings of risks, benefits and treatment alternatives of receiving invasive physiologic evaluation and he/she or his/her legally authorized representative provides 2. Exclusion criteria * Cardiogenic shock (systolic blood pressure \< 90mmHg or requiring inotropics to maintain blood pressure \> 90mmHg) ② Patients with a known hypersensitivity or contraindication to any of the following medications: statin, ezetimibe, heparin, aspirin, clopidogrel, prasugrel, ticagrelor * Non-cardiac co-morbid conditions are present with life expectancy \<2 year (per site investigator's medical judgment). * History of bleeding diathesis, known coagulopathy (including heparin-induced thrombocytopenia) ⑤ Patients with active pathologic bleeding ⑥ Gastrointestinal or genitourinary major bleeding within the prior 3 months. ⑦ Target lesion located in coronary arterial bypass graft