Interpretation of TCD spectral patterns detected during carotid artery stent interventions.

Purpose: To classify transcranial Doppler (TCD) spectral patterns and analyze the significance of the patterns in the determination of hemodynamic alterations occurring during filter-protected carotid artery stent (CAS) procedures.
Methods: Data on middle cerebral artery (MCA) monitoring and post-CAS diffusion weighted magnetic resonance imaging (DWMRI) were reviewed for 53 patients (45 men; mean age 67.6 ± 8.3 years) who underwent TCD evaluation before CAS and TCD monitoring during the procedure. TCD spectral patterns were classified according to the hemodynamic changes that occurred after different portions of the CAS procedures. The relationships among the spectral patterns and the frequency and location of new DWMRI lesions were analyzed.
Results: TCD spectral changes were classified into 4 patterns: (1) microemboli signals (53, 100%), (2) right-left collateral signals (31/53, 58%), (3) spectral suppression after balloon inflation (31/44, 70%), and (4) continuous spectral suppression after balloon removal (4/44, 9%). Even though microembolic signals were frequently observed during CAS, the new DWMRI lesions were more frequently observed outside of the cerebral territory (78%) rather than in the territory ipsilateral to CAS (47%). The presence of right-left collaterals was related to less severe balloon-related spectral suppression on ipsilateral MCA (p<0.05). Continuous spectral suppression appeared after stent deployment and balloon dilation and was immediately reversed after removal of the filter device.
Conclusion: The spectral patterns classified in the present study may prove useful in anticipating CAS procedure-related hemodynamic alterations. Close hemodynamic observation using these spectral patterns could be helpful in preventing serious complications during CAS.