Impaired cerebral vasoreactivity and risk of stroke in patients with asymptomatic carotid artery stenosis

Context Standards for treating patients with asymptomatic carotid artery st enosis have been difficult to establish because of the lack of evidence for factors influencing these patients' prognoses. However, preliminary eviden ce suggests that an alteration in. cerebral hemodynamic function may play a relevant role in the occurrence of stroke in patients with carotid artery disease. Objective To investigate the relationship between cerebrovascular reactivit y to hypercapnia and cerebrovascular events in patients with severe unilate ral asymptomatic carotid artery stenosis. Design and Setting Prospective, blinded longitudinal study conducted in an outpatient neurovascular department in Italy between June 1996 and April 19 98, with a median follow-up of 28.5 months. Patients Ninety-four patients with asymptomatic carotid artery stenosis of at least 70% (74 men; mean age, 71 years). Main Outcome measures Subsequent occurrence of cerebral ischemic events (tr ansient ischemic attack or stroke) or death, analyzed by cerebrovascular re activity to hypercapnia (measured by transcranial Doppler ultrasonography a nd calculated by the breath-holding index values in the middle cerebral art eries). Results The overall annual rate for all ischemic events was 7.9%. Seventeen patients (18%) had ischemic events, all but 1 of which were ipsilateral to the carotid artery stenosis. Among factors considered, only lower breath-h olding index values in the middle cerebral artery ipsilateral to carotid ar tery stenosis were significantly associated with the risk of an event (haza rd ratio, 0.09; 95% confidence interval, 0.02-0.38; P=.001, by multivariate analysis). Based on data from previously studied healthy subjects, the cut off of the breath-holding index for distinguishing between impaired and nor mal cerebrovascular reactivity was determined to be 0.69. Using this cutoff , the annual ipsilateral ischemic event risk was 4.1% in patients with norm al and 13.9% in those with impaired breath-holding index values. Conclusions These results suggest a link between impaired cerebrovascular r eactivity and the risk of ischemic events ipsilateral to severe asymptomati c carotid stenosis.