Flow convergence flow rates from 3-dimensional reconstruction of color Doppler flow maps for computing transvalvular regurgitant flows without geometric assumptions: An in vitro quantitative flow study

Objective: This study was designed to develop and test a 3-dimensional method for direct measurement of flow convergence (FC) region surface area and for quantitating regurgitant flows with an in vitro now system. Background: Quantitative methods for characterizing regurgitant flow events such as now convergence with 2-dimensional color flow Doppler imaging systems have yielded variable results and may not be accurate enough to characterize those more complex spatial events. Method: Four differently shaped regurgitant orifices were studied: 3 flat orifices (circular, rectangular, triangular) and a nonflat one mimicking mitral valve prolapse (all 4 orifice areas = 0.24 cm(2)) in a pulsatile now model at 8 to 9 different regurgitant flow rates (10 to 50 mL/beat). An ultrasonic flow probe and meter were connected to the now model to provide reference now data. Video composite data from the color Doppler flow images of the FC mere reconstructed after computer-controlled 180 degrees rotational acquisition was performed. FC surface area (S cm(2)) was calculated directly without any geometric assumptions by measuring parallel sliced flow convergence are lengths through the FC volume and multiplying each by the slice thickness (2.5 to 3.2 mm) over 5 to 8 slices and then adding them together. Peak regurgitant now rate (milliliters per second) was calculated as the product of S-dimensional determined S (cm(2)) multiplied by the aliasing velocity (centimeters per second) used for color Doppler imaging. Results: For all of the 4 shaped orifices, there was an excellent relationship between actual peak flow rates and 3-dimensional FC-calculated now rates with the direct measurement of the surface area of FC (r = 0.99, mean difference = -7.2 to -0.81 mL/s, % difference = -5% to 0%), whereas a hemielliptic method implemented with 3 axial measurements of the flow convergence zone from 2-dimensional planes underestimated actual flow rate by mean difference = -39.8 to -18.2 mL/s, % difference = -32% to -17% for any given orifice. Conclusions: Three-dimensional reconstruction of now based on 2-dimensional color Doppler may add quantitative spatial information, especially for complex how events. Direct measurement of 3-dimensional now convergence surface areas may improve accuracy for estimation of the severity of valvular regurgitation.