Changes in Doppler waveforms can predict pressure reduction across internal carotid artery stenoses.

Cerebral ischemia can result from either embolism or be due to hemodynamic failure. The purpose of this study was to evaluate whether Doppler waveforms, obtained distal to an internal carotid artery (ICA) stenosis, could predict the degree of hemodynamic compromise in terms of reduction in cerebral perfusion pressure. Forty-nine patients were examined consecutively with ultrasound Doppler prior to carotid endarterectomy. Pulsatility index (PI), pulse rise-time (RT), and systolic width (SW) were related to angiographic degree of stenosis and the ratio of distal ICA blood pressure to common carotid artery (CCA) blood pressure (ICA/CCA pressure ratio). The latter was determined during surgery. All three waveform parameters were significantly correlated with the ICA/CCA pressure ratio when calculated from the mean frequency curve (p less than 0.001). A reduction in ICA pressure of 20% could be predicted with an accuracy of 90-95%. Correlating the waveform parameters with arteriography was less convincing, reaching the level of statistical significance for PI only. ICA Doppler waveforms, obtained as distal in the neck as possible can accurately predict the degree of hemodynamic compromise. It is recommended as a simple adjunct to routine Doppler evaluation of carotid stenoses.