795–1 Quantitative Evaluation of Aortic Regurgitant Stroke Volume Using Vena Contracta Imaging by Color Doppler and Continuous Wave Doppler Echocardiography: An Animal Study with Quantified Aortic Insufficiency

The proximal flow convergence (FC) method has been used for quantification of regurgitation flows. Since high resolution flow images can often delineate color flow signals passing through the regurgitant orifice itself, the purpose of the present study was to demonstrate whether regurgitant stroke volumes (RSV) could be estimated using the imaged vena contracta (VC) of FC (i.e. the short proximal laminar portion of the regurgitant jet). In 6 sheep (3 in which a right coronary cusp and 3 in which non coronary cusp had been surgically trimmed to produce chronic aortic regurgitation [AR]) 21 hemodynamically different steady states were obtained pharmacologically 20 weeks after recovery from surgery. From magnified high resolution images the diameter of the VC of the flow imaged at 7.5mHz was measured as the smallest flow diameter in any part of the flow acceleration field (Figure). The velocity time integral (VTI) of AR obtained by color Doppler guided continuous wave (CW) Dopplerwas also recorded. Regurgitant stroke volume(RSV)were calculated by the formula: RSV=π(VC/2)2×VTI. Reference RSV was determined using pulmonary and aortic electromagnetic flow probes and meters balanced against each other. Reference RSV varied from 7.0 – 28 ml/beat (15±8.0 ml/beatl. regurgitant fraction from 0.20 to 0.59 (0.41±0.59). RSV estimated by vena contracta imaging on echocardiography correlated and agreed well with the EM RSVs (y=1.45×-6.30, r=0.96, SEE=3.6 ml/beat, p=0.0001). Our study indicates that a method for identifying and measuring the vena contracta of the FC region, when combined with CW velocities, can be used for quantifying AR stroke volume