A Preliminary Study On The Effect Of Carotid Artery Stenting On Cerebral Vascular Reactivity

Background and objective: cerebral vascular reactivity（CVR）is associated with increased risk of ipsilateral stroke in patients with carotid artery stenosis.Carotid angioplasty and stenting（CAS）can improve the CVR of patients with severe carotid stenosis,and the relationship between the hemodynamic status and CVR after operation is not clear.The purpose of this study was to analyze the changes of CVR before and after CAS,and the correlation between the changes of cerebral hemodynamics and the improvement of the ipsilateral CVR after CAS in patients with carotid artery stenosis.Methods: This study included 20 patients with unilateral internal carotid artery（ICA）stenosis who received CAS.Cerebral blood flow（CBF）and CVR were detected by single photon emission computed tomography（SPECT）combined with carbon dioxide（CO₂）inhalation for 7 days and 90 days after surgery.Scanning the first inspection,resting state,Through elbow vein bolus injection of 99 m Tc ECD 25 mci,after 30 min injection of subjects assigned them to check on the bed;the second examination,after a day,for CO₂ inhalation excited state,will link with a unidirectional valve is breathing mask and the gas tube connected tightly buckled on the subjects face,with uniform inhalation of 5% CO₂ and 95% O₂ mixed gas,adjusting the flow rate of gas in 4 L /min,enjoin its mouth respiratory 1 minute,after immediately give elbow venous bolus injection of 99 m Tc ECD 25 mci,60 min after injection of such as the first method for SPECT.Image processing: by the computer automatically take to show the plane and the brain anterior,middle and posterior cerebral artery blood supply area（OM+55mm）,in the cross section of the 2.95 mm layer thickness,continuous take four levels.Computer automatic of interest region（ROI）,the left and right symmetry of the 12 areas of the cerebral cortex of the brain.By the computer comes with software Neuro Matchautomatically calculate each cortical ROI and ipsilateral cerebellum radioactivity count ratio meter,standardization transformation of cerebral cortex ROI radioactivity counts and to form of the ratio of output data.Select a narrow side as the middle of the internal carotid artery and its main branches of the brain artery cortex ROI,reassume four layer average was studied.Cerebral blood flow（CBF）was defined as a patient with a layer of 4 ROI,a total of four layers of local cerebral blood flow and the mean,with the standard of radioactive count reflected.CVR is calculated using the formula CVR= [（CBFCO₂ inhalation-CBF resting）/ CBF resting] ×100%,CVR< 10% defined as decreased and Otherwise CVR in normal.After the operation,30 d,90±7d the patients were observed with recurrent stroke,neck vascular color Doppler ultrasound observation of stent patency,postoperative90±7d reevaluation of CVR.Relatively narrow side CAS postoperative and preoperative CVR changes if postoperative stenosis side CVR preoperative CVR increased more than or equal to 10% of a defined for CVR improvement after operation of the ROI and otherwise postoperative CVR did not improve.Use SPSS17.0 statistical software for statistical analysis,measurement data using a paired t-test,count data using chi square test,the difference（P < 0.05）are statistically significant.Results: all the patients were successfully CAS,no perioperative complications,CAS postoperative stenosis rate from 85.35%±9.66% before the improvement to17.5%±9.53%（P<0.01）.After operation,the side CVR of 90±7d was improved from 4%± 3.64% to 11.05%±4.47%（P<0.01）.Type 2,27 ROI,26 improvement;type 3,29 ROI,14 improvement（96% vs 48%;P<0.01）.Conclusions: Our study showed that CAS can improve the CVR of patients with severe carotid stenosis;preoperative impaired hemodynamic status was associated with improved CVR after CASsurgery,and more than 2 type ROI patients with type 3 ROI after CAS ischemia will receive more CVR improvement.