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Summary
We investigated the usefulness of cerebrovascular reserve (CVR) testing to predict severe hemodynamic changes during proximally protected carotid artery stenting. Of 90 patients referred, 63 eligible underwent complete evaluation of the extent of carotid artery disease and transcranial Doppler ultrasound (TCD) assessment of CVR by means of a breath-holding test and ophthalmic artery flow pattern evaluation. Periprocedural TCD monitoring of the ipsilateral middle cerebral artery flow was performed in 24 patients undergoing proximally protected procedure (requiring induction of flow arrest within internal carotid artery). Abnormal CVR was significantly less common in patients with unilateral compared to bilateral carotid artery disease (26.3 % vs. 76.9 %, p=0.02), while ophthalmic artery flow reversal was rare in patients with unilateral carotid artery disease (2.5 % vs. 42.9 %, p<0.01). During the induction of carotid flow arrest, the average mean flow velocity drop following external carotid artery occlusion was low (3.5 %, p=0.67) compared to the induction of complete flow arrest (32.8 %, p<0.01). Six patients had a total mean flow velocity drop >50 %, including 2 patients with normal pre-procedural CVR. Our results suggest that TCD evaluation of CVR is not a reliable predictor of hemodynamic changes induced during proximally protected carotid artery stenting in patients with unilateral carotid artery disease.
Key words
Cerebrovascular reserve * Carotid artery occlusion * Carotid artery stenting * Transcranial Doppler ultrasound * Cerebral collateral circulation
Introduction
Carotid artery disease is an important risk factor for a stroke development and it has been estimated that stenosis of the internal carotid artery is responsible for up to 15-20 % of the occurrence of all strokes or transient ischemic attacks (Sacco et al. 1995). The prevalence of carotid artery disease increases with age and its wide variability of clinical manifestation ranges from incidental asymptomatic findings to devastating or fatal stroke, with cerebral collateral circulation being considered one of the major modifying factors (Liebeskind 2003). In order to decrease the stroke burden, carotid endarterectomy has been used extensively to eliminate both hemodynamically significant stenosis as well as carotid artery plaques as a source of cerebral atheroemboli. Over time, carotid artery stenting has evolved into a reliable method so that it may now be offered as a first-line treatment to selected patients (Spacek and...