  This experimental in vitro work investigates material transport properties in
a model left ventricle in the case of aortic regurgitation, a valvular disease
characterized by a leaking aortic valve and consequently double-jet filling
within the elastic left ventricular geometry. This study suggests that material
transport phenomena are strongly determined by the motion of the
counterrotating vortices driven by the regurgitant aortic and mitral jets. The
overall particle residence time appears to be significantly longer with
moderate aortic regurgitation, attributed to the dynamics resulting from the
timing between the onset of the two jets. Increasing regurgitation severity is
shown to be associated with higher frequencies in the time-frequency spectra of
the velocity signals at various points in the flow, suggesting nonlaminar
mixing past moderate regurgitation. Additionally, a large part of the
regurgitant inflow is retained for at least one cardiac cycle. Such an increase
in particle residence time accompanied by the occurrence and persistence of a
number of attracting Lagrangian coherent structures presents favorable
conditions and locations for activated platelets to agglomerate within the left
ventricle, potentially posing an additional risk factor for patients with
aortic regurgitation.
