Apolipoprotein B (apoB) levels (which encompass all atherogenic lipoproteins, including LDL), Lp(a) levels, and carotid IPH are associated with both first-ever and recurrent ischemic stroke.

This cohort research project is to analyze:

1. Among patients with carotid artery atherosclerosis (stenosis 30-99%), to compare patients with and without IPH, as assessed by magnetic resonance (MR)-Plaque Imaging, in terms of apoB, Lp(a) levels and other cardiovascular risk factors. (IPH is a strong morphological sign of plaque vulnerability / instability and a strong marker of consecutive atheroembolic events).
2. Among patients with carotid artery atherosclerosis (stenosis 30-99%), to assess the risk of first-ever ischemic stroke in relation to apoB, Lp(a) levels, and presence of IPH, after adjusting for the cardiovascular factors (understanding this association can inform primary prevention).
3. Among patients with carotid artery atherosclerosis (stenosis 30-99%) with an ipsilateral ischemic stroke at baseline, to assess the risk of recurrent ipsilateral ischemic stroke in relation to apoB, Lp(a) levels, and presence of IPH, after adjusting for the cardiovascular factors. There will be a sensitivity analysis to assess if the association between Lp(a) and recurrent stroke is stronger in patients <60 years of age. (understanding this association can inform secondary prevention).

For the first and second aim, there will be a cross-sectional, case-control analysis. For the third aim, i.e. assessing recurrent ischemic stroke, there is prospective follow-up of at least 3 months up to 45 months.

Inclusion Criteria:

• Atherosclerotic carotid stenosis, North American Symptomatic Trial Collaborators (NASCET) method 30-99%
• Ability to undergo a neck MR for carotid plaque imaging
• Ability to undergo a follow-up of at least 1-year
• For the prospective, longitudinal part: Hemispheric ischemic stroke or retinal ischemia ipsilateral to the carotid stenosis, with symptom onset within 24 hours (these patients will be followed-up for recurrent ischemic stroke)

Exclusion Criteria:

• Carotid stenosis due to causes other than atherosclerosis (e.g. carotid dissection or post-actinic)
• Contraindication to MRI
• Lack of informed consent

Patients with ischemic stroke will be recruited in the Stroke Unit of the University Hospital Basel (primary center) and Zurich (partner center). Patients without ischemic stroke will be recruited in the outpatient neurovascular clinic at the University Hospital Basel (primary center) and Zurich (partner center), where around 250 patients with known carotid stenosis are regularly followed-up - clinically and with ultrasound.