Oral Presentations

Background: Patients with asymptomatic carotid stenosis (ACS) benefit much less from endarterectomy vs symptomatic CS. The number needed to treat (NNT) would be much lower among patients who could be identified as having higher risk. Purpose: We are studying imaging approaches to identify which ACS have a high enough risk to warrant endarterectomy. 238 patients with ACS 60% by Doppler (validated against NASCET angiographic measurements in 200 carotids) have undergone transcranial Doppler (TCD) embolus detection (two 1-hour sessions a week apart) to detect unstable plaque. Results: 25 (10.5%) of cases had microemboli (Emb) at baseline. There were no significant differences in traditional risk factors except for smoking. Emb were much more likely to have microemboli a year later (47.6% vs 1.8%; p0.0001), had higher plasma total homocysteine (17.86 10.8 vs 10.17 4.9 micromol/L; p 0.0001), were more likely to be current smokers (40% vs 15%, p0.008), to have peripheral vascular disease (44% vs 21%, p0.014), more likely (but not significantly) to die or have myocardial infarction (14% vs 8%, p0.36), had more TIA's (14.3% vs 2.4%; p0.03), more endarterectomies (9.5% vs 0.6%; p0.002), and were 7.9 times more likely to have a stroke during the first year of followup (19% vs 2.4%; p0.006). Conclusion: ACS with unstable plaque defined by TCD microemboli may warrant endarterectomy, if surgery is as safe in this group; this hypothesis should be studied in a RCT. We are now studying MRI and 3-D ultrasound characteristics of plaque such as ulceration and plaque surface roughness, as other possible indicators of high risk.