1© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Simulations of Hypertrophic Obstructive Cardiomyopathy (HOCM) in a Human Heart Left Ventricle using ANSYS/CFX/Fluent Vladimir Kudriavtsev (Intevac), Metin Ozen, Can Ozcan (Ozen Engineering)

2© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Considerable Interest Lately: LV, HOCM, Heart Fluid Structure Interactions

3© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Human Heart Model Model courtesy of Dr. Jingwen Hu, PhD University of Michigan Transportation Research Institute Real Geometry of LV mm MITRAL AORTIC LV-left ventricle

4© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Schematic diagram of a patient with a normal heart (left) and a patient with hypertrophic cardiomyopathy (right). Nishimura R A et al. Circulation. 2003;108:e133-e135 Copyright © American Heart Association, Inc. All rights reserved. Wall thickening Septal subaortic bulge, Flow obstruction Mechanism of dynamic outflow tract obstruction. The upper schematic shows a representation of the mitral leaflets. The elongated mitral leaflets that are drawn into the Left Ventricular Outflow Tract during early systole with midsystolic prolonged systolic anterior motion- septal contact, malcoaptation of the mitral leaflets, and the resultant posteriorly directed jet of mitral regurgitation.

5© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Simulated 3D LV Geometry – fully parametric in Design Modeler Imposed wall motion Parametric Geometry Definition

6© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara s_of_TTE#Left_Ventricle Typical Heart Left Ventricle LV Dimensions

7© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 CFX Model Definition Wall Motion is Prescribed as sin time dependent in Radial and Axial Inlet pressure is prescribed as sin or cos time dependent wave, which is always positive

8© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Oscillating CFX-ANSYS 2-way FSI Tutorial CFX, P=600Pa We increase boundary pressure up to 600Pa. Tutorial Fails, negative mesh volume P>680Pa Fails, when “angle” <90 deg “angle”

9© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Valve Hyper-elastic Transient Simulations Valve Initial Position Moonley-Rivlin Model; Pressure extrapolation from Transient Simulation. Requires multiple and small time steps Valve fully open

10© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 First CFX-ANSYS 2Way FSI Results: Flow Valve Interactions Coupled flow simulation fails due to negative mesh when valve deformation significant Hyper-elastic valve model (stand alone) with external pressure allows significant deformation, when not coupled with CFX

11© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 No Valves, blocking flow effect of valves is simulated using transient (sin or cos) pressure pulse at Mitral Inlet and CFX Outflow Boundary condition (does not allow backflow) for Aortic Valve Moving Wall to simulate displacement and ejection effect during systole and volume filling effect during diastole Stroke Volume, displacement volume and pressure magnitude, heart rate are matched Example of Systolic-Diastolic Transient Flow in Left Ventricle (CFX) Example of Steady State Simulation, Clearly grossly inadequate for the mechanics involved

12© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Mass Flow – Mitral and Aortic Re=5281 Aortic Outflow Positive— Mitral inflow Negative- Aortic outflow Mitral inflow Zero—Mitral inflow during systolic contraction Close to zero during diastolic expansion.

13© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Diastolic Phase

14© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Beginning of Systolic Contraction End of Diastolic Wall motion

15© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Systolic –flow squeeze action Wall motion Recirculations are getting suppressed No mitral outflow

16© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 End of Systolic Phase No recirculations are left due to flow squeeze action No mitral outflow Aortic outflow

17© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Transient 2-way FSI Valve Motion Simulation with Remeshing (FLUENT, 2D) Small Septum Hump Larger Septum Hump, valve is entrained closer to septum wall NO WALL MOTION No Aortic Valve/No aortic outflow blockage diastolic

18© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Transient 2-way FSI Valve Motion Obstruction Mechanism Septum Hump Systolic wall motion direction From this moment and on as LV wall and septum move towards each other during systole (creating ejection into aortic valve) MITRAL leaflet that is already deflected and obstructing diastolic flow with Venturi effect of lower pressure behind it only gets pushed further by mechanical forces and fluid forces to do more obstruction as lower pressure zone behind it fails to create enough lateral push

19© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Transient 2-way FSI Valve Motion Obstruction Mechanism Systolic wall motion direction Venturi effect of lower pressure behind it only gets pushed further by mechanical forces and fluid forces to do more obstruction as lower pressure zone behind it fails to create enough lateral push Systolic wall motion direction

20© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Moving Wall and Systolic Engagement Valve: E= 2.5MPa, v=0.33 Inlet and wall conditions are copy/paste from your simulation setup. Inlet condition: 2000 Pa * abs(sin(t*3.85)) Wall Movement: 0.005*abs(sin(t*3.85)) or 0.015*abs(sin(t*3.85)) End of diastolic flow obstruction (valve laterally deflected) Recirculation formed Recirculation pushed toward hump and aorta

21© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Systolic Obstruction and Lateral Entrainment of Mitral Leaflet Systolic flow obstruction Recirculation blocks aortic outflow, Creates low pressure zone Entrains valve laterally into Obstructive position as wall is moving inward

22© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Transient 2-way FSI Valve Motion Obstruction Mechanism -2 Towards the end of systole, instead of being pushed away into normal position, leaflet is entrained laterally right into the aortic exit path – thus blocking outflow and this positioning is stable. No forces at play to return it back to normal. Systolic wall motion direction Septum Hump

23© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Obstruction Mechanism -3 (Large Hump & Long Valve Leaflet) Towards the end of diastolic period Mitral valve leaflet deflected Septum Hump End Diastolic, Valve Leaflet Flip Flapped

24© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Obstruction Mechanism -4 (Large Hump & Long Valve Leaflet) xxxxxx Septum Hump Flow Through Mitral Valve Stopped. Complete Flow Obstruction – Full contact of hump and mitral valve. Computation failed, flow stopped!!!! Heart Stopped as Well! Early Systolic

25© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Echocardiographic results - HOCM Flapping and flow obstruction during ejection (systole) Hump Touchdown during expansion (diastole) Both valves closed End of diastole and Aortic valve closed Aortic opened, mitral closed Mitral opened, aortic closed

26© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Left Ventricular Outflow Diastolic Aortic Mitral Septum Hump(bulge) Systolic Large Outflow Small Outflow

27© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Summary of Work -1 -Studied LV geometries and more detailed models, developed simplified parametric transient 3D model with moving walls using CFX; -Studied “2 way FSI” Capabilities of ANSYS/CFX for moving elastic valve of fixed thickness [oscillating.* Tutorial]. Found limitations of method when large deformation are involved due to negative grid and deficiencies of grid interpolation in CFX; -Studied separate valve motion transient analysis with hyper- elastic valve material model and extrapolated pressure loads from transient CFX flow model. Demonstrated capability to simulate transient valve motion in the solid ANSYS module;

28© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Summary of Work -2 -Coupled valve motion with transient flow in moving ANSYS/CFX, failed interpolated meshes due to inability to re- mesh; -Used Fluent/ANSYS 2-way FSI with re-meshing to study deforming valve problem in 2D; -demonstrated interaction of 2D moving valve with moving mesh for simulations with hump and without hump on wall septum. -demonstrated mechanism of mitral valve flow obstruction for HOCM. Next steps: conduct similar analysis in 3D or find way to solve in ANSYS /CFX environment (try shell models with no thickness for valve to ease mesh interpolation)

29© 2014 ANSYS, Inc. ANSYS Users Regional Conference, Santa Clara 2014 Left Ventricular Outflow