Atherosclerosis is a chronic, systemic and progressive disease affecting different arterial blood vessels in the body. Atherosclerotic lesions silently progress from small plaques to severe stenosis and may remain asymptomatic for years. Unstable plaques and stenosis (also called vulnerable plaques), however, are prone to rupture leading to myocardial infarction, or stroke. The proliferation of the small arteries that are distributed to the outer and middle coats of the larger blood vessels (vasa vasorum) and within the atherosclerotic plaques (neovascularization) are inherently linked with the atherosclerotic plaque development, plaque inflammation and vulnerability. By injecting ultrasound contrast agents (microbubbles) into the blood stream, it is possible to detect this microcirculation of the vessel wall and the neovascularization within the atherosclerotic plaque using a contrast-enhanced ultrasound (CEUS) imaging technique. Particularly, CEUS of the carotid artery has been introduced as a non-invasive technique to improve detection of carotid atherosclerosis and to evaluate the presence of carotid plaque neovascularization which has emerged as a new marker for plaque vulnerability. The project investigates the predictive value of the detection of carotid plaque neovascularization on CEUS imaging in patients with asymptomatic carotid artery stenosis regarding the progression of the carotid atherosclerotic lesion and future vascular events including myocardial infarction, stroke or vascular intervention. The investigators hypothesize that neovascularization within the carotid lesion will significantly be more pronounced in patients with progressive carotid lesions and in patients suffering future vascular events during. The project will support the concept that intraplaque neovascularization is associated with plaque instability and vulnerability and therefore, the use of CEUS may provide an additional non-invasive, simple, safe, and reliable imaging modality to risk stratify individuals. The identification of vulnerable that are at increased risk of rupture by identification of intraplaque neovascularization is expected to improve the prediction of future vascular events and thus allow for better treatment selection. It will help the clinician to further risk stratify carotid stenosis. Particularly, it will help to identify unstable carotid stenosis that may already benefit from invasive therapy as carotid thromboendarterectomy and stenting.

Inclusion Criteria:

• Patients age > 18 years
• Asymptomatic (no history of cerebrovascular event in the corresponding vessel territory) ≥30% carotid stenosis on standard carotid ultrasound

Exclusion Criteria:

• History of previous carotid endarterectomy or carotid stenting.
• Heart failure (HYHA III or IV)
• Myocardial infarction (<7d)
• Severe pulmonal-arterial hypertension (pulmonal arterial pressure >90mmHg) based on clinical information (history of pulmonal arterial pressure, dyspnea on exertion New York Heart Association (NYHA) III and NYHA IV)
• pregnancy (pregnancy test in patients of childbearing age: <50 years and/or less than 2 years after menopause)
• Follow-up is not considered feasible

In-and out-patients referred to our ultrasound laboratory for carotid ultrasound for a clinical indication (preoperative, carotid murmur, known carotid lesion) will be ask to participate in this clinical study and will be asked to undergo study carotid ultrasound including CEUS.