Attenuated plaque ≥ 5mm by intravascular ultrasound(IVUS) was reported to be high risk for distal embolism in Acute coronary syndrome(ACS). The purpose of this study is to assess the effect of thrombus aspiration catheter and distal protection device (filter wire; Filtrap™) in the aforementioned subgroup of patients at high risk for distal embolism.

Inclusion Criteria:

Patients who were diagnosed as ACS and meet the following criteria.

• Patients with acute myocardial infarction or unstable angina within 2 months from onset.
• Patients who have severe coronary stenosis which require PCI and in whom attenuated plaque ≥ 5mm (longitudinally) by IVUS before PCI is observed prior to balloon dilatation and stent deployment.

Exclusion Criteria:

• Patients who need balloon expansion (including small diameter balloon) for IVUS catheter crossing.
• Patients who were resuscitated after dead on arrival
• Graft lesion or in-stent restenosis lesion
• Patients on dialysis or renal failure (Cr>1.5mg/dl).
• Left main trunk lesion
• Target vessel size is <2.5mm or >5mm
• Ineligible for PCI
• Lactating and (possibly) pregnant woman or having possibility of pregnant
• Patients who are considered ineligible by the attending physician