Influence of structural geometry on the severity of bicuspid aortic stenosis

Abstract

Doppler-derived gradients may overestimate total pressure loss in degenerative and prosthetic aortic valve stenosis (AS) due to unaccounted pressure recovery distal to the orifice. However, in congenitally bicuspid valves, jet eccentricity may result in a higher anatomic-to-effective orifice contraction ratio, resulting in an increased pressure loss at the valve and a reduced pressure recovery distal to the orifice leading to greater functional severity. The objective of our study was to determine the impact of local geometry on the total versus Doppler-derived pressure loss and therefore the assessed severity of the stenosis in bicuspid valves. On the basis of clinically obtained measurements, two- and three-dimensional computer simulations were created with various local geometries by altering the diameters of the left ventricular outflow tract (LVOT; 1.8–3.0 cm), orifice diameter (OD; 0.8–1.6 cm), and aortic root diameter (AR; 3.0–5.4 cm). Jet eccentricity was altered in the models from 0 to 25°. Simulations were performed under steady-flow conditions. Axisymmetric simulations indicate that the overall differences in pressure recovery were minor for variations in LVOT diameter (<3%). However, both OD and AR had a significant impact on pressure recovery (6–20%), with greatest recovery being the larger OD and the smaller recovery being the AR. In addition, three-dimensional data illustrate a greater pressure loss for eccentric jets with the same orifice area, thus increasing functional severity. In conclusion, jet eccentricity results in greater pressure loss in bicuspid valve AS due to reduced effective orifice area. Functional severity may also be enhanced by larger aortic roots, commonly occurring in these patients, leading to reduced pressure recovery. Thus, for the same anatomic orifice area, functional severity is greater in bicuspid than in degenerative tricuspid AS.

Numerical Model of Full-Cardiac Cycle Hemodynamics in a Total Artificial Heart and the Effect of Its Size on Platelet Activation

“…Computational Fluid Dynamics (CFD) and Fluid Structure Interaction (FSI) models were previously utilized in simulations of various mechanical valves [11–17] and MCS devices [18,19]. Sonntag et al [20] employed FSI model to simulate the flow in the ReinHeart TAH device, where the diaphragm motion is controlled by a piston rather than an air pump.…”

Reverse Area and Gradient Mismatch: The Discordance of a Large Valve Area and High Gradients

“…Thus, with larger LVOT diameters, there is an elevation in both Doppler ∆P max and invasive ∆P net that is disproportionate to the degree of area stenosis. However, Doppler and invasive gradients are close to each other with a reverse area/gradient mismatch noted by both modalities [18][19][20]. Thus for a given geometric AVA, a larger LVOT diameter The relationship between GOA, EOA, and the coefficient of orifice contraction (EOA/GOA).…”

“…9.4), there is an increase in pressure loss as the eccentric jet collides with the ascending aortic wall with resultant energy loss due to heat, flow separation, and vortex formation. The latter will also cause a decrease in the absolute and relative P rec [17][18][19][20]. As a result of both increased in pressure loss as well as decreased P rec , both the Doppler-and catheter-derived ∆P mean will be higher compared to the GOA.…”

Turbulent Kinetic Energy Assessed by Multipoint 4-Dimensional Flow Magnetic Resonance Imaging Provides Additional Information Relative to Echocardiography for the Determination of Aortic Stenosis Severity

“…Background phase errors were compensated by fitting a plane to the phase of static tissue. [26][27][28][29] Subsequently, Bayesian processing was performed to simultaneously calculate mean velocities and intensities of velocity fluctuations per image voxel along each velocity encoding direction and for each time point in the cardiac cycle. Voxelwise TKE values were then computed according to 17 :…”