A phantom study to evaluate the effects of a local sectional stiffness on aortic hemodynamics

A strong association has been established between cardiovascular complications and aortic stiffness which results from aging or vascular disease. The reduced wall distension alters the aortic hemodynamics and compromises the ventricular performance. This paper is a preliminary phantom study that experimentally evaluates the effects of a localized stiffness on aortic hemodynamics, with respect to the stiffness length and position relative to an upstream aortic site. Rigid prints were externally applied to the phantom thus simulating local sectional stiffness, and MRI was used to obtain the time varying flow rate and cross-sectional area (CSA). Pressure waves were measured using optical fiber sensors. Eight stiffness combinations were examined, and characteristic parameters were assessed for each case. As expected, the pulse pressure and input impedance were increased, and the peak flow rate was reduced. Moreover, the global compliance decreased as the stiffness was brought closer to the proximal site and/or covered longer aortic segments. The phantom buffering function was thus impaired. However, the regional pulse wave velocity was not notably affected by any of the stiffness configurations. Additionally, the compliance of the intact site upstream to the stiffening locations was reduced. We conclude that the effects of a local stiffness extend to neighboring sites. The standard global stiffness measuring approaches such as carotid-femoral wave velocity might not be sufficient to detect such localized stiffening.