Doppler Duplex for the Evaluation of the Degree of Stenosis in Carotid Arteries in the Rat

This study evaluates the accuracy of the Doppler duplex technique for providing reliable information about the level of stenosis in microanastomoses. Stenoses ranging between 30 and 85 percent of the cross-sectional area of carotid arteries were evaluated in rats. Peak systolic velocities were measured in prestenotic, stenotic, and poststenotic segments, using the duplex technique. Surgical results with duplex measurements were expressed as percentage of stenosis (calculated from a ratio of two cross-sectional areas), and later correlated. The correlation coefficient between the two sets of measurements was 0.82 (p < 0.01), and the hypothesis of a simple linear relationship was clearly accepted (p = 0.92). Results of the study show that duplex measurements become increasingly unreliable in stenoses with severity less than 50 percent. With increasing degrees of stenosis (50 percent and above), the variance of measurements with duplex decreases. According to the data, the limiting value for the duplex method appears to lie at about 85 percent. When methods for continuous measurement of flap perfusion indicate a hindrance of inflow, Doppler duplex can provide valuable information about the causes. This technique can be used clinically for the evaluation of microanastomoses in 1-mm vessels. In clinical cases, if a 50 percent or more stenosis is diagnosed by duplex technique, the measurement should be repeated within 1 to 2 hr. If the stenosis persists or intensifies, revision should be considered.