Interaliasing distance of the flow convergence surface for determining mitral regurgitant volume: a validation study in a chronic animal model

Abstract

Objectives: We aimed to validate a new flow convergence (FC) method that eliminated the need to locate the regurgitant orifice and that could be performed semiautomatedly.

Background: Complex and time-consuming features of previously validated color Doppler methods for determining mitral regurgitant volume (MRV) have prevented their widespread clinical use.

Methods: Thirty-nine different hemodynamic conditions in 12 sheep with surgically created flail leaflets inducing chronic mitral regurgitation were studied with two-dimensional (2D) echocardiography. Color Doppler M-mode images along the centerline of the accelerating flow towards the mitral regurgitation orifice were obtained. The distance between the two first aliasing boundaries (interaliasing distance [IAD]) was measured and the FC radius was mathematically derived according to the continuity equation (R(calc) = IAD/(1 - radicalv(1)/v(2)), v(1) and v(2) being the aliasing velocities). The conventional 2D FC radius was also measured (R(meas)). Mitral regurgitant volume was then calculated according to the FC method using both R(calc) and R(meas). Aortic and mitral electromagnetic (EM) flow probes and meters were balanced against each other to determine the reference standard MRV.

Results: Mitral regurgitant volume calculated from R(calc) and R(meas) correlated well with EM-MRV (y = 0.83x + 5.17, r = 0.90 and y = 1.04x + 0.91, r = 0.91, respectively, p < 0.001 for both). However, both methods resulted in slight overestimation of EM-MRV (Delta was 3.3 +/- 2.1 ml for R(calc) and 1.3 +/- 2.3 ml for R(meas)).

Conclusions: Good correlation was observed between MRV derived from R(calc) (IAD method) and EM-MRV, similar to that observed with R(meas) (conventional FC method) and EM-MRV. The R(calc) using the IAD method has an advantage over conventional R(meas) in that it does not require spatial localization of the regurgitant orifice and can be performed semiautomatedly.