Left and right ventricular flows by Doppler echocardiography: serial measurements in patients with aortic regurgitation during exercise, cold pressor stimulation, and vasodilation. To test the practicality of Doppler echocardiography to measure serial change, biventricular outputs were measured in 15 patients with aortic regurgitation during control periods and during interventions of bicycle exercise, cold pressor stimulation, and vasodilation. Biventricular stroke volumes were measured in 10 normal subjects for validation of methods and differed by 2.8%. Reading errors were 3.7%. Signal quality improved between the first and last observation (p less than 0.05). Velocity signals were corrected for intercept angles, which averaged 12 and 19 degrees for right heart flows and 31 and 32 degrees for the left side of the heart in all subjects. Negative correlations occurred between intercept angles and the chronologic order in which the patients were studied for left (p = 0.02) and right (p = 0.05) flows. Mean flow areas varied 9% in the left ventricle and 20% in the right ventricle. Total variability for measuring flow determined from control values was 11% to 13%. When twice the variability was used as the detectable level of change, only exercise provoked real increases in biventricular flows in the majority of patients. We conclude that serial measurements of flow by Doppler echocardiographic methods had to exceed 20% to 25% to achieve significant change. Measuring intercept angle, resolving flow area, and learning are variables that need greater emphasis. 