Predictive value of diamox stress brain SPECT for the use of selective shunting during carotid endarterectomy (CEA)

The purpose of this study was to evaluate whether diamox stress brain SPECT is an adequate method of predicting the need for selective shunting during CEA and determining the indication group for the use of the prophylactic shunt. Fifty-one CEAs were performed in 51 patients (45 symptomatic, 6 asymptomatic) with selective shunting based on the change of consciousness during carotid clamping under regional anesthesia. Both carotid arteries were evaluated by angiography. Basal/diamox stress brain SPECT using 99mTc-ECD were performed in the same day within 2 weeks before CEA. One investigator performed visual assessment of regional cerebral blood flow (rCBF) and cerebrovascular reactivity (rCVR) on SPECT. The SPECT images were divided into four groups: Type N/N, normal rCBF/normal rCVR; Type R/N, reduced rCBF/normal rCVR; Type N/R, normal rCBF/reduced rCVR; Type R/R, reduced rCBF/reduced rCVR. The severity of reduced rCBF and rCVR was also graded. The results of SPECT images were compared with the severity of contralateral carotid stenosis. Selective shunting was performed in 10 patients who had change of consciousness during carotid clamping. Selective shunting was higher in patients with reduced rCVR (Type N/R, R/R) regardless of rCBF than normal rCVR and with severe contralateral carotid stenosis than other (p=0.001). All of 5 patients having severely reduced rCVR and Type R/R with severe contralateral carotid stenosis performed selective shunting. Incidence of selective shunting according to the type of SPECT and degree of contralateral carotid stenosis are shown in the table. Diamox stress brain SPECT may be helpful in the preoperative evaluation of risky patients for cerebral ischemia during carotid clamping. Patients having severely reduced rCVR or reduced rCBF/rCVR with severe contralateral carotid stenosis may be indicated for prophylactic shunt during CEA