Introduction:
Grading aortic stenosis (AS) has traditionally relied on measuring hemodynamic parameters of transvalvular pressure gradient, ejection jet velocity, or estimating valve orifice area. Recent research has highlighted limitations of these criteria at effectively grading AS in presence of left ventricle (LV) dysfunction. We hypothesize that simulations coupling the aorta and LV will provide meaningful insight into myocardial biomechanical derangements that accompany AS. Reference data from the normal ventricle should first be obtained.
Methods:
A multi-domain cardiac model with representative anatomy and material properties was used to create AS simulations. Finite element analysis was performed with ABAQUS FEA®. An anisotropic hyperelastic model was assigned to the aorta and LV passive properties, while time-varying elastance function governed LV active response. Mild and severe AS were created by restricting the aortic valve orifice area.
Results:
Global LV myofiber end systolic (ES) stress (mean±SD) was 9.31±10.33 kPa at baseline (no AS), 13.13±10.29 kPa for mild AS, and 16.18±10.59 kPa with severe AS. Mean LV myofiber ES strains were -22.4±8.7%, -22.2±8.9%, and -21.9±9.2%, respectively. Mild and severe AS had significant stress elevation compared to baseline (mild AS vs base; p<0.01, severe AS vs base; p<0.001) and when compared to each other (p<0.01). See
Figure 1
. Ventricular regions that experienced greatest magnitude ES stress were (severe AS vs baseline) basal inferior (39.87±14.73 vs 30.02±12.08 kPa; p<0.01), mid-anteroseptal (32.29±11.56 vs 24.79±12.00 kPa; p<0.001), and apex (27.99±8.44 vs 23.52±10.19 kPa; p<0.001).
Conclusions:
Isolated AS in a normal heart was simulated, and significantly elevated LV myofiber stress was quantified. This data serves as a comparison to future studies that will incorporate patient-specific ventricular geometries and material parameters, aiming to correlate LV biomechanics to AS severity.
Comparison of automated stroke volume evaluation for determination of valve orifice area by the continuity equation with the conventional approach in aortic stenosis