The prevalence of cerebral infarcts in the Asymptomatic Carotid Surgery Trial (ACST) in relation to prior contralateral symptoms.

BACKGROUND: The ACST has randomised over 1670 patients to determine if carotid endarterectomy (CEA) prolongs stroke free survival versus best medical treatment alone. Some patients have had contralateral symptoms to the side under investigation, for which CEA may have been performed. This study aims to determine the prevalence of hemispheric cerebral infarcts in relation to prior contralateral symptoms. METHODS: Patients with preoperative CT or MR scans were divided into those with prior contralateral stroke, cortical TIA, amaurosis fugax or no symptoms. RESULTS: There were 1144 patients with preoperative CT and 170 patients with MR scans. Incidence of contralateral hemispheric CT and MR infarcts were 19% (222/1144) and 20% (34/170) respectively. Those with prior contralateral stroke (141) had the highest incidence of hemispheric CT infarcts (62%). Those with TIA (129) had a 30% incidence of CT infarct. Incidence of hemispheric CT infarcts were 17% with amaurosis fugax (46) and 10% with no prior symptoms (803). Mantel-Haenszel test for linear association was significant (p < 0.001) for increasing severity of symptoms. Considering MR scans, those with prior contralateral stroke (17) had the highest incidence of hemispheric MR infarcts (53%). Patients with TIA (23) or amaurosis fugax (6) had a 27% incidence of MR infarction. Those with no prior symptoms (121) had a 14% incidence of MR infarcts. Mantel-Haenszel test was significant (p < 0.001). CONCLUSIONS: In the ACST, currently asymptomatic patients have an incidence of contralateral hemispheric CT and MR infarcts proportional to the severity of prior contralateral symptoms.