FSI Analysis for Heart Surgery

Most biological processes involve fluid-structure interactions (FSI). Here we present a heart, patient-specific, right/left ventricle and patch combination model with fluid-structure interactions. The objective is to evaluate and optimize a surgical procedure and patch design for a human heart pulmonary valve replacement/insertion*.

Cardiac Magnetic Resonance (CMR) imaging studies were performed at the Children's Hospital Boston and the Harvard Medical School. These studies acquired ventricle geometry, flow velocity and flow rate for healthy volunteers and patients needing right ventricle pulmonary valve replacement. With this information, FSI models were constructed to perform mechanical analyses and assess right ventricle cardiac functions.

Figure 1 gives the stacked MRI contours and right and left ventricle inner/outer surface plots showing patch, scar, and valve positions, and also the finite element meshes used.

Fig. 1. Re-constructed 3D ventricle geometry: contours, geometry, valve and patch positions, meshes

For the study, CMR data were used to adjust and validate the model so that predicted right ventricle volumes reached good agreement with CMR measurements (less than 3% difference). Figures 2 & 3 show some results from the FSI model. In the above movie, we show the maximum principal strain variation calculated from a patient-specific Right Ventricle/Left Ventricle/Patch FSI Model.

The modeling results indicate that:

• patient-specific CMR-based computational modeling can provide a valuable assessment of right ventricle cardiac functions;

• pulmonary valve replacement with a smaller patch and more aggressive scar removal can lead to reduced stresses and strains in the patch area and may lead to improved recovery of right ventricle functions;

• detailed knowledge of flow shear stress and ventricle stress/strain distributions provide useful information for the optimization of the surgical procedure and the patch.

This analysis illustrates the very valuable use of ADINA FSI models in biological studies. For more details, please refer to the reference below.

Fig. 2. Velocity plots at different phases showing flow patterns in the right ventricle

Fig. 3. Some principal stress and principal strain plots

Reference

C. Yang, D. Tang, I. Haber, T. Geva, P. J. del Nido, “In Vivo MRI-Based 3D FSI RV/LV Models for Human Right Ventricle and Patch Design for Potential Computer-Aided Surgery Optimization”, Computers & Structures, 85, 988-997, 2007.

*Courtesy of Prof. D. Tang, Worcester Polytechnic Institute