Quantitative assessment of chronic aortic regurgitation with 3- dimensional echocardiographic reconstruction: Comparison with electromagnetic flowmeter measurements

Two-dimensional echocardiography and color Doppler are useful in the qualitative assessment of aortic regurgitation. However, color Doppler planar methods are not accurate in quantifying regurgitant flow, in part because of the complex geometry of aortic regurgitant flow events. Three-dimensional echocardiographic reconstruction is a new technique that provides dynamic 3- dimensional images of intracardiac color flow jets. We sought to determine whether the measurement of aortic regurgitant jet volume by 3-dimensional echocardiography correlated with the true regurgitant volume, measured by electromagnetic flowmeter in vivo, to accurately reflect the severity of aortic regurgitation. We performed volume-rendered 3-dimensional echocardiography in 6 sheep with surgically induced chronic eccentric aortic regurgitation. We obtained a total of 22 aortic regurgitation states by altering loading conditions. Instantaneous regurgitant flow rates were obtained by aortic and pulmonary electromagnetic flowmeters. The maximum aortic regurgitant jet volume by 3-dimensional echocardiography and the maximum jet area by 2-dimensional echocardiography were measured and compared with electromagnetic flowmeter data. By electromagnetic flowmeter, aortic regurgitant flow rate varied from 0.14 to 3.1 L/min (mean 1.25 ± 0.78); aortic regurgitant stroke volume varied from 1 to 34 mL/beat (mean 12 ± 8), and regurgitant fraction varied from 3% to 42% (mean 25% ± 12%). The maximum jet volume by 3-dimensional echocardiography correlated very well with the aortic regurgitant stroke volume (r = 0.92; P < .0001), with the mean regurgitant flow rate (r = 0.87; P < .0001), and with the regurgitant fraction (r = 0.87; P < .0001) derived from electromagnetic flowmeter. Both intraobserver and interobserver variability on the measurement of the jet volume by 3-dimensional echocardiography were excellent (r = 0.98; P < .0001 and r = 0.90; P < .001, respectively). The maximum jet area by 2-dimensional echocardiography did not correlate with the aortic regurgitant stroke volume (r = 0.41; P = not significant) and related poorly with the regurgitant fraction (r = 0.52; P < .05) by electromagnetic flowmeter. Dynamic 3- dimensional echocardiography can allow better determination of the geometry of the aortic regurgitant jet and may assist of quantifying the severity of aortic regurgitation.