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Silent CT-Brain Embolic Infarcts and Risk of Ipsilateral Hemispheric Events and Stroke in Patients with Asymptomatic Internal Carotid Artery Stenosis

Steve Kakkos, Michael Sabetai, Thomas Tegos, John Stevens, Maura Griffin, George Geroulakos, Andrew N. Nicolaides.
Imperial College, London, United Kingdom.

OBJECTIVES: The aim was to test the hypothesis that silent embolic infarcts on CT-Brain scans can predict ipsilateral neurological hemispheric events and stroke in patients with asymptomatic internal carotid artery stenosis.

METHODS: In a prospective multicentre natural history study, 821 patients with asymptomatic carotid stenosis graded with duplex scanning who had CT-Brain scans on admission to the study were followed 6 monthly to a maximum of 8 years. Duplex scans were reported centrally and stenosis was expressed as a percentage in relation to the normal distal internal carotid (NASCET criteria). CT-brain scans were reported centrally by a neuroradiologist. Large cortical (n=8), small cortical (n=15), discrete subcortical (n=72) and basal ganglia (n=51) ipsilateral infarcts, present in 146 patients, were considered likely to be “embolic” and were classified as such. Other infarct types, lacunes (n=15), watershed (n=9) and the presence of diffuse white matter changes (n=95) were not considered to be “embolic”.

RESULTS: During a mean follow-up of 44.6 months (range 6 months to 8 years), 102 ipsilateral hemispheric neurological events (AF n=16, TIA n=39 and stroke n=47) were observed, while 138 patients died and 24 were lost to follow-up. In patients with 60-99% stenosis (n=462) the cumulative event free survival at 8 years was 0.63 (4.6% annual event rate) in the presence of “embolic” infarcts and 0.81 (2.4% annual event rate) in their absence (log rank p=0.032). In patients with <60% stenosis (n=359) the presence of “embolic” infarcts was not associated with increased risk (log rank p=0.65). In patients with 60-99% stenosis the cumulative stroke free survival was 0.71 (3.6% annual stroke rate) in the presence of “embolic” infarcts and 0.92 (1.0% annual stroke rate) in their absence (log rank p=0.002) In the subgroup of moderate, 60-79% stenosis, (n=216) the cumulative TIA or stroke free survival in the presence and absence of “embolic” infarcts was 0.61 (4.9% annual rate) and 0.89 (1.4% annual rate) respectively (log rank p=0.003).

CONCLUSIONS: The results indicate that the presence of silent “embolic” infarcts can identify a high risk group for ipsilateral hemispheric neurological events and stroke, and may prove useful in the management of patients with moderate asymptomatic carotid stenosis.

AUTHOR DISCLOSURES: S. Kakkos, None; M. Sabetai, None; T. Tegos, None; J. Stevens, None; M. Griffin, None; G. Geroulakos, None; A.N. Nicolaides, None.