Doppler echocardiographic determination of stroke volume and cardiac output : clinical validation of two new methods using the apical window

Two methods of measuring stroke volume and cardiac output with pulsed Doppler twodimensional echocardiography were developed and validated against the thermodilution technique in 39 patients, 33 of which were in an intensive care unit. With the use of the apical four-chamber view, a mitral inflow method combined the velocity of left ventricular inflow at the mitral anulus with the crosssectional area of the anulus calculated from its diameter at middiastole (area = z r2). From the apical five-chamber view a left ventricular outflow method combined the velocity of left ventricular outflow with the cross-sectional area of the aortic anulus calculated from its diameter during early systole (parastemal long-axis view). Measurements with the mitral inflow and left ventricular outflow methods were obtained in 35 of 39 (90%) and 39 of 39 (100%) patients, respectively. Validation of the mitral method excluded patients with mitral regurgitation (n = 11) and validation of the left ventricular outflow method excluded those with aortic regurgitation (n = 4). Good correlations were observed between thermodilution and Doppler measurements of stroke volume and cardiac output for both the mitral anulus method (R = .96 and .87, respectively) and the left ventricular outflow method (R = .95 and .91, respectively). The results of the two methods correlated well with each other in patients without regurgitant valve lesions. A greater interobserver variability was observed with the mitral anulus method, which was related solely to greater variability in measuring the annular diameter. In patients with mitral regurgitation, left ventricular inflow volume was always greater than left ventricular outflow stroke volume while the inverse was true in those with aortic regurgitation. Thus, stroke volume and cardiac output can be accurately measured from the cardiac apex with mitral inflow or left ventricular outflow methods when applicable. Comparison of volumes obtained with these two methods may prove valuable in quantitating the severity of mitral or aortic regurgitation. Circulation 70, No. 3, 425-431, 1984. RECENT technological developments have made possible the application of Doppler echocardiography to the measurement of stroke volume and cardiac output. Methods previously validated consist of measuring ascending aortic flow from the suprasternal window or pulmonary arterial flow from the parasternal window.1-' These methods work on the premise that the velocity of blood flow determined from the Doppler From the Section of Cardiology, Baylor College of Medicine, The Methodist Hospital, Houston. Computational assistance was provided by the CLINFO Project, funded by grant RR-00350, Division of Research Resources, National Institute of Health, Bethesda. Address for correspondence. Miguel A. Quinones, M.D., Section of Cardiology, The Methodist Hospital, 6535 Fannin -MS, F-1001, Houston, TX 77030. Received Jan. 9, 1984; revision accepted April 26, 1984. Presented at the 56th Annual Scientific Sessions of The American Heart Association, November 1983, Anaheim, CA. Vol. 70, No. 3, September 1984 shifts of the reflected sound waves are uniformly distributed throughout the cross section of the vessel so that the product of the area under the velocity curve times the cross-sectional area of the vessel is equal to the volume of blood passing through the vessel. Among other factors, the velocity profile within a vessel and the accuracy of the measurements of the cross-sectional area of the vessel affect the accuracy of Doppler flow measurements. For instance, in patients with aortic sclerosis or stenosis the velocity profile in the ascending aorta becomes nonlaminar and a greater dispersion of velocities is observed within the vessel, invalidating the use of ascending aortic flow velocity for measuring cardiac output. When pulsed Doppler echocardiography is used, the vessel cross-sectional area should ideally be measured at the site of sample volume position for greater accuracy. Images adequate 425 by gest on O cber 5, 2017 http://ciajournals.org/ D ow nladed from