BACKGROUND: The 2011 American Heart Association Guidelines on the management of asymptomatic carotid disease recommends that carotid endarterectomy (CEA) (with carotid artery stenting (CAS) as an alternative) may be considered in highly selected patients with 70-99% stenoses. However, no guidance was provided as to what "highly selected" meant. This caveat is, however, important as up to 95% of asymptomatic individuals undergoing prophylactic CEA or CAS will ultimately undergo an unnecessary procedure. Even if the procedural risk following CEA or CAS could be reduced to 0%; 93% of patients would still undergo an unnecessary intervention. This, coupled with growing awareness that the risk of stroke in medically treated patients appears to be diminishing, has led to a renewed drive towards identifying patients with the highest risk of suffering a stroke whilst on medical therapy in whom to target CEA/CAS.

METHODS: Review of clinical and/or imaging based scoring systems, predictive algorithms and imaging parameters that may be associated with an increased (or decreased) risk of stroke in patients with asymptomatic carotid disease.

RESULTS: Parameters associated with an increased risk of late stroke include: (a) silent infarction on CT/MRI; (b) stenosis progression; (c) hypoechoic plaques or GSM <15; (d) irregular plaques; (e) evidence of spontaneous embolization on TCD; (f) AHA plaque types IV-V, VI; (g) MR diagnosed IPH; (h) plaque area >80 mm(2); (i) juxta-luminal black area >10 mm(2); and (j) tandem intracranial disease.

CONCLUSIONS: A number of imaging parameters have been shown to be predictive of an increased risk of late stroke in previously asymptomatic patients. None have been independently validated, but many could easily be evaluated in natural history studies or randomized trials in order to identify a "high risk for stroke" cohort in whom CEA/CAS could be prioritized.