This is an observational and prospective cohort study to examine whether the addition of IVUS plaque morphological evaluation to FFR haemodynamic assessment of non-culprit lesions in NSTEACS patients will better predict MACEs.

IMPACT-NSTEACS is a prospective, single-centre and dynamic observational study. The study population consists of NSTEACS patients who undergo FFR in lesions with intermediate to severe angiographic stenosis. Then, FFR-guided PCI is performed, followed by morphological assessment based on IVUS in all FFR-negative lesions (FNLs). After discharge all patients receive optimal medication treatment and are followed up clinically. On the basis of follow-up angiography, MACEs are further adjudicated as occurring at FNLs or not.

Clinical Inclusion Criteria:

1. Moderate to high risk NSTEACS requiring invasive strategy based on current guidelines and local clinical practice.
2. Patient agrees and is able to follow all protocol procedures.

Clinical Exclusion Criteria:

1. STEMI or SCAD.
2. Hemodynamic instability (e.g. cardiogenic shock, refractory ventricular arrhythmias, acute and severe conduction system disease and left ventricular ejection fraction ≤30%).
3. Contraindication for FFR, PCI, IVUS and OMT (e.g. severe allergy to antiplatelet drug or contrast, significant bleed within the past 6 months, bleeding diathesis and serum creatinine ≥2.5 mg/dl).
4. PCI within 6 months or any prior CABG.
5. Anticipated life expectancy <3 year.
6. Pregnancy
7. Unwilling or unable to provide informed consent

Imaging Inclusion Criteria

1. Patients must have at least > 1 de novo lesion in a native coronary segment with a visually estimated diameter stenosis of between 40 and 90 %.
2. Successful FFR-guided PCI performed in all major epicardial coronary arteries (including their branches): PCI for all lesions a) with 40%-90% diameter stenosis and FFR<0.8 and b) with ≥90% diameter stenosis.
3. The FFR-negative lesions must be available for assessment of IVUS.

Imaging Exclusion Criteria:

1. Target lesion reference diameter <2.0 mm.
2. Anatomic conditions precluding FFR and IVUS (e.g. marked calcification or tortuosity, chronic total occlusion or thrombus).
3. After successful FFR-guided PCI, no FNL is left.
4. Any remaining lesion with diameter stenosis ≥90% or FFR<0.8 after PCI.
5. Left main coronary artery lesion.
6. CABG planned by the investigators according to extent and severity of coronary artery disease.

For study enrollment, we screen patients with NSTEACS combination of unstable angina and non-ST-segment elevation myocardial infarction according to current guidelines. Once all clinical inclusion criteria and no clinical exclusion criteria are met, patients must sign the informed consent and undergo invasive coronary angiography (ICA). During ICA patients will be further analyzed for eligibility using angiographic inclusion and exclusion criteria. Patients will be enrolled into the study once the IVUS measurement is delivered after successful FFR-guided PCI.