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
Laminar flow through a conduit is equal to the mean velocity times the cross-sectional area of the orifice. Therefore, volume is equal to the time-velocity integral multiplied by the crosssectional area. In aortic stenosis, flow in the stenotic jet is laminar and the aortic valve area should be equal to the volume of blood ejected through the valve divided by the time-velocity integral of the aortic jet velocity recorded by continuous- No. 3, 452-459, 1986. ACCURATE ASSESSMENT of the hemodynamic severity of aortic stenosis from clinical and echocardiographic findings is frequently difficult, particularly in the elderly patient. ' -4 Recently, several studies have demonstrated a good correlation between aortic valve gradients measured at cardiac catheterization and gradients estimated by continuous-wave Doppler echocardiography and a modification of the Bernoulli equation.5-9 However, the pressure gradient through a stenotic valve is largely dependent on flow, which in turn depends on left ventricular performance and the presence of concomittant valvular regurgitation.
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