ISNVD Abstract Book

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MONDAY – FEBRUARY 20, 2012 2:15pm-2:30pm We can now select ACS patients who require carotid endarterectomy or stenting (Andrew Nicolaides, UK) Until recently our current practice has been based on the results of the ACAS and ACST 2 randomized controlled trials (RCT), which provided the first scientific evidence that in patients with asymptomatic carotid stenosis (ACS) > 60-70% can reduce the annual risk of stroke from 2% to 1%. In these trials the perioperative stroke was 2.3% and the number needed to treat (NNT) to prevent one stroke per year was 83. Modern medical intervention includes life style changes and aggressive risk factor modification such as treating hypertension and hypercholesterolemia to predetermined targets, achieved by appropriate adjustment of drug dosages. This aggressive medical therapy was not applied to the patients in the ACAS or ACST trials. Observational studies published after 1995 show that in patients with moderate to severe ACS the annual stroke risk is not 2.5-2% but closer to 1.0-0.5% with the authors suggesting a 70% reduction in stroke rates as a result of modern medical therapy. However, information from observational studies is level III and any recommendations based on the findings are grade C. This is because in such observational studies, bias from patient selection based on the ACAS and ACST results and the publications between 1995 and 2000 that echolucent plaques are unstable and dangerous cannot be excluded. Only RCT can produce level I evidence and grade A recommendations. In addition, the suggestion that the risk of ischemic stroke has been reduced by 70% as a result of modern medical therapy is not compatible with the actual results of RCT in asymptomatic and symptomatic patients showing that statins can reduce stroke by 20-27%. Assuming optimal medical therapy can reduce the overall ischemic stroke rate by 30%, there will still be patients with ACS >70% with an annual stroke rate >2% that may require surgery. Several methods are now available that can identify high risk patients or even stratify patients according to risk. They consist of (a) methods that identify the ulcerated plaque or the plaque with an intraluminal thrombus producing microemboli and (b) methods that identify the unstable plaque. They are summarised below. The presence of microembolic signals on transcranial Doppler (TCD) can identify a high risk group as demonstrated by several studies 7-8 and a meta-analysis of 6 studies. In the ACES study 8 the risk of ipsilateral stroke was 7% at one year. In the meta-analysis, microembolic signals were present in 195(17%) of 1144 patients with ACS and this group contained 17(57%) of the 30 strokes that occurred during follow-up. A more recent study 9 has demonstrated that the combination of microembolic signals and presence of a hypoechoic plaque identify a subgroup with even a higher risk. The method of recording microembolic signals is now well established and equipment is commercially available. The presence of silent embolic infarcts on CT-Brain scans (discrete subcortical, small cortical and non-lacunar basal ganglia infarcts) identify a high risk subgroup as shown by the ACSRS prospective natural history study with 1121 patients with a 6 month to 8 year follow-up (mean 4 years) 10 . In the 60-99% stenosis group the presence of embolic infarcts identified a group of 61(11%) of 572 patients that had an annual stroke rate of 4.4%. Future prospective studies should use MRI-Brain scans which are more sensitive than CT in identifying such lesions. In the ACSRS study, the combination of plaque features (% stenosis, low GSM indicating a hypoechoic plaque, plaque area, presence of discrete white areas without acoustic shadow indicating neovascularisation) could stratify patients according to stroke risk. 11 This risk varied from 0.5% per year to 10% per year. Of the 923 patients with >70% stenosis, the annual ipsilateral stroke rate was 6% in 34. The predicted risk correlated well with the observed risk. Patients ≥2% annual stroke risk consisted of a group of 250(27%) of the 923. This group contained 36(63%) of the 54 strokes. This method is practical provided ultrasonographers are trained on equipment settings and image capture. Such training can be done in one day. In addition, semi-automated user friendly software is now commercially available that can do the image analysis and calculate the annual stroke risk adding only 10 minutes to the ultrasound examination. In conclusion, identification of high risk subgroups and stroke risk stratification is now possible
using several methods. These methods need to be validated in the medical arm of RCT of medical therapy vs combined medical plus surgical therapy. Data from such studies will provide us with appropriate cut-off points that can be applied to routine clinical practice. In the mean time many patients can be spared from an unnecessary operation using the following criteria for considering patients with ACS for carotid endarterectomy: 1) ACS patients with two or more microemboli in one hour of TCD monitoring. 2) ACS patients with one or more microemboli at baseline, and echolucent plaque or 3) ACS patients with annual stroke risk >2% according to risk stratification based on plaque texture analysis. Stenting for asymptomatic stenosis carries a nearly double risk of stroke than CE. Thus, it should only be considered for patients who meet one of the above criteria, and have lesions unsuitable for surgery, such as a high carotid bifurcation, restenosis following prior endarterectomy, or radiation fibrosis. No financial disclosures to report.
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Page 55 and 56: POSTER ABSTRACTS Monday, February 2
Page 57 and 58: POLITECNICO DI MILANO mlagana@dongn
Page 60 and 61: Background Iron deposition in clini
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Introduction Cardiac Effects In The
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Acetazolamide as a medical treatmen
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A model of filtration and solute tr
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Characteristics of patients who mai
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FINDINGS ON VENOGRAPHY IN MS PATIEN
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The 2 nd Annual ISNVD Scientific Me
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