Silent embolic infarcts on computed tomography brain scans and risk of ipsilateral hemispheric events in patients with asymptomatic internal carotid artery stenosis.
OBJECTIVE
This study tested the hypothesis that silent embolic infarcts on computed tomography (CT) brain scans can predict ipsilateral neurologic hemispheric events and stroke in patients with asymptomatic internal carotid artery stenosis.


METHODS
In a prospective multicenter natural history study, 821 patients with asymptomatic carotid stenosis graded with duplex scanning who had CT brain scans were monitored every 6 months for 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 criteria used by the North American Symptomatic Carotid Endarterectomy Trialists. CT brain scans were reported centrally by a neuroradiologist. In 146 patients (17.8%), 8 large cortical, 15 small cortical, 72 discrete subcortical, and 51 basal ganglia ipsilateral infarcts were present; these 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-8 years), 102 ipsilateral hemispheric neurologic events (amaurosis fugax in 16, 38 transient ischemic attacks [TIAs], and 47 strokes) occurred, 138 patients died, and 24 were lost to follow-up. In 462 patients with 60% to 99% stenosis, the cumulative event-free rate at 8 years was 0.81 (2.4% annual event rate) when embolic infarcts were absent and 0.63 (4.6% annual event rate) when present (log-rank P = .032). In 359 patients with <60% stenosis, embolic infarcts were not associated with increased risk (log-rank P = .65). In patients with 60% to 99% stenosis, the cumulative stroke-free rate was 0.92 (1.0% annual stroke rate) when embolic infarcts were absent and 0.71 (3.6% annual stroke rate) when present (log-rank P = .002). In the subgroup of 216 with moderate 60% to 79% stenosis, the cumulative TIA or stroke-free rate in the absence and presence of embolic infarcts was 0.90 (1.3% annual rate) and 0.65 (4.4% annual rate), respectively (log-rank P = .005).


CONCLUSIONS
The presence of silent embolic infarcts can identify a high-risk group for ipsilateral hemispheric neurologic events and stroke and may prove useful in the management of patients with moderate asymptomatic carotid stenosis.
Kakkos
Stavros K
SK
Academic Vascular Surgery, Imperial College, London, United Kingdom.
Sabetai
Michael
M
Tegos
Thomas
T
Stevens
John
J
Thomas
Dafydd
D
Griffin
Maura
M
Geroulakos
George
G
Nicolaides
Andrew N
AN
D000368:Aged; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging; D016893:Carotid Stenosis / Q000150:complications* / Q000000981:diagnostic imaging / Q000401:mortality; D002544:Cerebral Infarction / Q000000981:diagnostic imaging* / Q000209:etiology / Q000401:mortality; D018450:Disease Progression; D005260:Female; D006801:Humans; D020766:Intracranial Embolism / Q000000981:diagnostic imaging* / Q000209:etiology / Q000401:mortality; D002546:Ischemic Attack, Transient / Q000000981:diagnostic imaging / Q000209:etiology* / Q000401:mortality; D053208:Kaplan-Meier Estimate; D008297:Male; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D020521:Stroke / Q000000981:diagnostic imaging / Q000209:etiology* / Q000401:mortality; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D018616:Ultrasonography, Doppler, Duplex