The effect of chordae tendineae on systolic flow. 
When using Computational Fluid Dynamics to simulate ventricular blood flow in the heart, it has been common practice to neglect the effect of the sub-valvular apparatus and the trabeculae on the flow conditions.  In this study, we analyze the effect of neglecting the chordae tendineae on the fluid flow and pressure drop.  To test the assumption we use a previously developed dynamic 3D model of the left ventricle, aorta and valves that is based on 3D echocardiographic recordings.  To this model we add the chordae tendineae as a sub-grid model.  The previously developed 3D model for the left ventricle during systole is based on real-time three-dimensional echocardiography (RT3DE) recordings of a 30 years old female volunteer.  The segmented ventricular wall does not include details of the aorta and the mitral valve, so these were reconstructed.  The subgrid model for the flow across the chordae tendineae is based on the Actuator Line Method, which means that they are represented by drag coefficients.  The analysis shows that the effect of the chordae tendineae on the pressure drop and work efficiency of the normal heart during systole is minor, and it seems that for simulating ventricular fluid flow and pressure drop during systole, one can follow the current practice and ignore the chordae.  However, there can be local effects such as small vortices behind the chordae.  Whether such effects are important for a particular application must be evaluated for the given case.