Accuracy of cardiac output measured by continuous wave doppler echocardiography during dynamic exercise testing in the supine position in patients with coronary artery disease

Abstract

To estimate the accuracy of cardiac output measured by continuous wave Doppler echocardiography from the suprasternal notch and the utility of this method for evaluating left ventricular function during dynamic exercise, simultaneous thermodilution and Doppler cardiac output were measured in 34 patients with coronary artery disease during multistage ergometer exercise in the supine position. Cardiac output was measured at rest and during each stage of exercise. Twenty-five of the 34 patients whose thermodilution curves were adequate for analysis were studied during exercise. The correlation coefficient for the two methods was 0.85 at rest and 0.84 during exercise. Differences between the two methods were not significant at rest but were significant during exercise, with the thermodilution method giving the higher values. Underestimation by the Doppler method is probably due to technical problems and changes in aortic diameter during exercise.The 25 patients were classified into two groups according to pulmonary artery wedge pressure at peak exercise. There were 11 patients in Group 1 pressure (≥20 mm Hg at peak exercise) and 14 in Group 2 pressure (<20 mm Hg at peak exercise). There were significant differences in the change in cardiac index and in peak aortic velocity from rest to peak exercise between the two groups. A significant linear correlation between the percent change in peak aortic velocity and in pulmonary artery wedge pressure from rest to peak exercise was observed (r = −0.66, p < 0.001).These results indicate that : 1) continuous wave Doppler echocardiography can provide a noninvasive, reliable technique for measuring cardiac output during dynamic exercise testing in the supine position; and 2) the percent change in peak aortic velocity from rest to peak exercise may be a useful index for discriminating between patients with a normal versus an elevated pulmonary artery wedge pressure during exercise testing.