Objective: By using transcranial Doppler (TCD) it is possible to measure blood flow velocities within the circle of Willis. In this study, TCD was performed before and after carotid endarterectomy (CEA) with the aim to describe cerebral hemodynamics after normalization of the carotid artery blood flow.
Methods: Thirty CEA patients were consecutively entered into the TCD study, whereas 15 patients were referred for postoperative TCD for various clinical reasons. All 45 patients were investigated by using TCD: first preoperatively, then during the first few days after CEA before discharge from the hospital, and finally 3 to 12 months later. In addition, all patients underwent duplex investigation of the internal carotid artery the day before surgery and 3 months postoperatively. For the analysis, the patients were divided into two groups, one with (S-group), suspected postoperative neurologic complications/symptoms and another one without (C-group). Six patients were assigned to the S-group and 37 to the C-group, the latter including two patients who underwent bilateral CEAs.
Results: In the whole study group,a significant postoperative increase in systolic flow velocity was recorded bilaterally in the middle cerebral artery (MCA) as measured some days after surgery. The patients in the S-group showed high blood flow velocities mainly in the MCA on the ipsilateral side. A contralateral flow velocity increase did not occur in patients with very severe contralateral stenosis or occlusion (n = 9) if the late follow-up investigation was chosen as a reference value. Twenty patients in the C-group formed a subgroup with high blood pressure and/or headache postoperatively (CB-group) The other 19 patients were referred to as the CA-group. The CB- and S-groups showed more pronounced vessel disease in internal carotid artery on the contralateral side combined with lower collateral capacity in the circle of Willis compared to the CA-group. In the S-group the mean +/- standard deviation peak systolic velocity in ipsilateral MCA increased from a preoperative value of 0.71 +/- 0.22 m/sec to 2.23 +/- 0.72 m/sec (P <.005). In the CB-group, we observed a bilateral MCA blood flow velocity increase from 0.72 +/- 0.18 to 1.35 +/- 0.56 m/sec (P <.0001) on the ipsilateral side and from 0.82 +/- 0.37 to 1.28 +/- 0.66 m/sec (P < 0.001) on the contralateral side. In the CA-group, we observed minor bilateral blood flow velocity increases in the MCA, from 0.79 +/- 0.25 m/sec to 1.03 +/- 0.33 m/sec on the ipsilateral (P <.001) and from 0.70 +/- 0.17 m/sec to 0.93 +/- 0.26 m/sec on the contralateral side (P <.005). At the follow-up 3 to 12 months after surgery, the MCA flow velocities had returned to normal.
Conclusions: Soon after surgery, blood flow velocity increases often bilaterally in the MCA. However a contralateral flow velocity increase did not occur in patients with very severe contralateral stenosis or occlusion if the late follow-up investigation was chosen as a reference value. The clinical significance of bilateral flow velocity increases is uncertain, but very high blood flow velocities might be a signal for cerebrovascular hyperperfusion. In those patients, increased postoperative surveillance is recommended.