EFFECTIVE REGURGITANT ORIFICE AREA BY THE COLOR DOPPLER FLAW CONVERGENCE METHOD FOR EVALUATING THE SEVERITY OF CHRONIC AORTIC REGURGITATION- AN ANIMAL STUDY

Background The aim of the present study was to evaluate dynamic change s in aortic regurgitant (AR) orifice area with the use of calibrated e lectromagnetic (EM) flowmeters and to validate a color Doppler flow co nvergence (FC) method for evaluating effective AR orifice area and reg urgitant volume. Methods and Results In 6 sheep, 8 to 20 weeks after s urgically induced AR, 22 hemodynamically different states were studied . Instantaneous regurgitant flow rates were obtained by aortic and pul monary EM flowmeters balanced against each other. Instantaneous AR ori fice areas were determined by dividing these actual AR flow rates by t he corresponding continuous wave velocities (over 25 to 40 points duri ng each diastole) matched for each steady state. Echo studies were per formed to obtain maximal aliasing distances of the FC in a low range ( 0.20 to 0.32 m/s) and a high range (0.70 to 0.89 m/s) of aliasing velo cities; the corresponding maximal AR flow rates were calculated using the hemispheric flow convergence assumption for the FC isovelocity sur face. AR orifice areas were derived by dividing the maximal flow rates by the maximal continuous wave Doppler velocities. AR orifice sizes o btained with the use of EM flowmeters showed little change during dias tole, Maximal and time-averaged AR orifice areas during diastole obtai ned by EM flowmeters ranged from 0.06 to 0.44 cm(2) (mean, 0.24+/-0.11 cm(2)) and from 0.05 to 0.43 cm(2) (mean, 0.21+/-0.06 cm(2)), respect ively. Maximal AR orifice areas by FC using low aliasing velocities ov erestimated reference EM orifice areas; however, at high AV, FC predic ted the reference areas more reliably (0.25+/-0.16 cm(2), r=.82, diffe rence=0.04+/-0.07 cm(2)). The product of the maximal orifice area obta ined by the FC method using high AV and the velocity time integral of the regurgitant orifice velocity showed good agreement with regurgitan t volumes per beat (r=.81, difference=0.9+/-7.9 mL/beat). Conclusions This study, using strictly quantified AR volume, demonstrated little c hange in AR orifice size during diastole. When high aliasing velocitie s are chosen, the FC method can be useful for determining effective AR orifice size and regurgitant volume.