Spectral analysis of Doppler signal in the prophylaxis of ischemic cerebrovascular accidents in extra- and/or intracranial carotid and vertebral systems.

Using continuous-wave spectral analysis of Doppler signal (SADS) and/or pulsed-wave transcranial Doppler ultrasonography (TCD-US) we examined 263 patients with ischemic cerebrovascular diseases (ICVD) symptoms in the carotid and vertebrobasilar (V-B) systems. The degree of stenosis was established by taking into consideration the parameters of the spectrum of frequency (systolic peak velocity--SV; end-diastolic velocity--DV); the ratio between SV of internal carotid artery (ICA) and common carotid artery (CCA); the ratio between DV of ICA and CCA as well as the value of the spectral broadening (SB) index. The diminution of DV in CCA with increased values of Pourcelot's circulatory resistance index (RP) and spectral broadening index (SB) as compared with the controlateral part, but with apparent increase (over 3.5 kHz) of SV in ICA was constantly observed in significant stenoses of extracranial ICA. Our observations have pointed out that when proximal ICA occlusion is being formed slowly and progressively, ECA (whose increased circulatory resistance under normal conditions reflects diminished diastolic velocities) gradually takes over the hemodynamic characteristics of ICA which is expressed by increased DV, approximating DV and ICA. This situation may give rise to erroneous interpretations.