Abstract
Background and Purpose: Carotid artery stenting procedures are increasingly being performed with devices such as the MO. MA or the Parodi system that involve endovascular clamping of the common carotid artery, thus exposing the ipsilateral hemisphere to the risk of hypoperfusion. The aim of the present study was to look for predictors of carotid clamping intolerance by means of transcranial Doppler. Patients and Methods: We analysed the findings of an earlier Italian multicentre prospective study ( SCITEA, Italian Cooperative Study of Transcranial Doppler in Carotid Endarterectomy) in which 513 consecutive patients (males/females 397/ 116, mean age 67 +/- 7 years, mean carotid stenosis 81 +/- 11%, NASCET method) scheduled to undergo carotid endarterectomy had been investigated non-invasively with transcranial Doppler, and we correlated the data obtained preoperatively with the need to insert a shunt during surgery as an index of intolerance to carotid clamping. Results: Four hundred and thirty-nine patients (85.6%) underwent surgery without and 74 (14.4%) with the insertion of a shunt. Patients who needed a shunt ( intolerant) had a significantly higher decrement in mean flow velocity in the ipsilateral middle cerebral artery (MCA) after compression of the ipsilateral common carotid artery (71.8 +/- 22 vs. 30.6 +/- 24%) and were significantly more likely to have non-recruitable collateral pathways (75 vs. 18%). Logistic regression analysis confirmed that an MCA decrement of >85% (p = 0.005) and no potential collateralization (p = 0.011) were independent predictors of clamping intolerance. Combining the results of both compression tests ( MCA decrement and collateral recruitment) yielded a sensitivity of 64%, a specificity of 99%, a positive predicted value of 88%, a negative predicted value of 95% and an overall accuracy of 95% in predicting shunt insertion. Conclusions: The preoperative assessment of recruitable collaterals and of maximal decrement in MCA mean flow velocity after carotid compression are useful predictors of carotid clamping intolerance. The criteria derived from carotid endarterectomy need to be applied and validated in a prospective series of patients undergoing carotid artery stenting procedures.