Comparison of high pulse repetition frequency and continuous wave doppler echocardiography in the assessment of high flow velocity in patients with valvular stenosis and regurgitation

↵aAddress for reprints: Arthur E. Weyman, MD, Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Fruit Street, Boston, Massachusetts 02114.

Abstract

Continuous wave Doppler echocardiography has proved useful in detecting and quantitating the high velocity flow disturbances that characterize many stenotic and regurgitant valvular lesions. Pulsed Doppler echocardiography, in contrast, is limited in its ability to quantitate the high velocities that are detected. Recently, new pulsed Doppler systems have been developed that employ high pulse repetition frequencies and can theoretically measure higher flow velocities than those measured by the standard pulsed Doppler systems. To determine the ability of high pulse repetition frequency Doppler echocardiography to accurately measure high velocity flow signals in comparison with the continuous wave method, 80 patients undergoing routine echocardiographic examination for the assessment of valvular heart disease were studied using both techniques.

A total of 113 high velocity flow disturbances were detected in 68 patients. In 41 instances, the maximal velocities by the two methods were within 0.5 m/s of each other. In 68 of the 113 high velocity lesions, however, the high pulse repetition frequency technique underes timated the peak velocity found with continuous wave Doppler echocardiography by more than 0.5 m/s. Comparison of the peak velocities recorded by the two methods for the total group showed no significant correlation (r = 0.04, p = NS). Comparison of the difference in peak velocities obtained by the two techniques with the maximal continuous wave velocity (n = 94, r = 0.70, slope = 0.71) suggested that the underestimation becomes greater as the peak velocity increases. Fifteen of the study patients with aortic stenosis subsequently underwent catheterization. Using the simplified Bernoulli equation (p2 - p1 = 4V²), an estimated peak aortic gradient was calculated from both the continuous wave and high pulse repetition frequency data. The predicted continuous wave gradient correlated well with catheterization data (r = 0.89, p = 0.001); however, there was no significant (r = 0.49, p = NS) relation between the gradient predicted from the high pulse repetition frequency Doppler recordings and the measured gradient.