No serum biomarker has qualified for clinical use until now. However several biomarkers, especially markers of inflammatory or proteolytic activity seem to promising in the identification of vulnerable plaques. Moreover, recent study confirmed that contrast-enhanced ultrasound imaging(CEUS) can visualize intraplaque neovascularization and represent the plaque vulnerability. In this study we try to identify indicators through analysis of the relationship between plaque neovascularization seen by CEUS and well known biomarkers such as serum matrix metalloproteinase(MMP)-2, MMP-9, cathepsin family(L,S,V), cystatin C, lipoprotein phospholipase A2, and hs-crp

Inclusion Criteria:

• patients with carotid plaques size more than 2mm by carotid ultrasound

Exclusion Criteria:

• known allergy to albumin, or to the ultrasound contrast agent
• the patients with history of carotid endarterectomy and carotid stent
• acute myocardial infarction, cardiogenic shock
• connective tissue disease and malignancy
• creatinine clearance lower than 30ml/min and the history of dialysis

The patients were selected from those who admitted due to chest pain and underwent carotid duplex ultrasound examination at KyungHee university medical center, Seoul, South Korea.