Cerebrovascular reactivity in carotid artery occlusion: possible implications for surgical management of selected groups of patients

The aim of this study was to use transcranial Doppler ultrasonography to investigate cerebrovascular reactivity to hypercapnia in the middle cerebral arteries of patients with carotid occlusion with different outcomes.Cerebrovascular reactivity to hypercapnia was calculated with the breath-holding index (BHI). Patients with unilateral carotid occlusion were divided as follows: asymptomatic (20 patients), transient ischemic attack (TIA) (20 patients), minor (20 patients) and major stroke (14 patients). Values of BHI homolateral to the carotid occlusion were compared with those of 25 healthy subjects and 34 stroke patients without significant carotid stenosis.BHI values were comparable in healthy controls, non stenotic stroke patients and asymptomatic occluded patients. BHI values of patients with symptomatic occlusion were significantly lower than those of the above-mentioned groups (P<0.0001). Moreover, the reduction of BHI was significantly associated with the extent of the neurological impairment. In fact, BHI values were significantly higher in TIA than in minor and major stroke (P<0.0001) and in minor than in major stroke patients (P<0.02). Finally, we found that a BHI value homolateral to carotid occlusion of 0.69 can be considered the cut-point for distinguishing between symptomatic and asymptomatic patients.Prospective studies are needed to demonstrate if the presence of this threshold value may help in selecting a subset of patients with asymptomatic carotid occlusion or with transient or mild neurological deficit with the highest probability of benefiting from surgical therapy.