Ex Vivo Methods for Informing Computational Models of the Mitral Valve

Abstract

Computational modeling of the mitral valve (MV) has potential applications for determining optimal MV repair techniques and risk of recurrent mitral regurgitation. Two key concerns for informing these models are (1) sensitivity of model performance to the accuracy of the input geometry, and, (2) acquisition of comprehensive data sets against which the simulation can be validated across clinically relevant geometries. Addressing the first concern, ex vivo micro-computed tomography (microCT) was used to image MVs at high resolution (~40 micron voxel size). Because MVs distorted substantially during static imaging, glutaraldehyde fixation was used prior to microCT. After fixation, MV leaflet distortions were significantly smaller (p<0.005), and detail of the chordal tree was appreciably greater. Addressing the second concern, a left heart simulator was designed to reproduce MV geometric perturbations seen in vivo in functional mitral regurgitation and after subsequent repair, and maintain compatibility with microCT. By permuting individual excised ovine MVs (n=5) through each state (healthy, diseased and repaired), and imaging with microCT in each state, a comprehensive data set was produced. Using this data set, work is ongoing to construct and validate high-fidelity MV biomechanical models. These models will seek to link MV function across clinically relevant states.

A comprehensive pipeline for multi‐resolution modeling of the mitral valve: Validation, computational efficiency, and predictive capability

“…The annular dimensions in the normal and dilated states were taken from the previously published in vivo data . The dimensions of the normal annulus were set to 30 × 24 mm, and the dilated dimensions were 33 × 30 mm . The repaired annulus dimensions were set to be the same as for the normal annulus; PMs were attached to the adjustable rods, and the whole MV complex was mounted into the Georgia Tech Cylindrical Left Heart Simulator (CLHS) …”

“…The positions of PMs were adjusted to achieve normal coaptation behavior defined as follows: (1) anterior leaflet occupying 2/3 of A2‐P2 diameter, (2) coaptation length of 5 mm, and (3) no noticeable leakage measured in pressure and flow rate. The details of experimental setup and related experimental procedures can be found in previous studies . The MV was then imaged in 3 configurations that simulated (1) normal (physiological), (2) dilated (mimicking the effects of myocardial infarction), and (3) repaired (flat‐ring annuloplasty repair) states.…”

Computational Pre-surgical Planning of Arterial Patch Reconstruction: Parametric Limits and In Vitro Validation

“…Following the success in patient-specific computational fluid dynamics (CFD) simulations,1,27,35 the pre-surgical planning concept, based on soft-tissue finite element models (FEM) has also been demonstrated 3,36,37,41,42. Particularly, the implementation of FEM in the pre-surgical planning of complex heart valve repair procedures is well-established 4,23,30 – 32,44. Likewise, computational soft-tissue models are essential in the evaluation of stenting procedures of aorta, pulmonary and carotid arteries 8,25,33.…”

Impact of simulated MitraClip on forward flow obstruction in the setting of mitral leaflet tethering: An in vitro investigation

“…The baseline MAA was adjusted and set to achieve leaflet coaptation length of >7 mm prior to data collection for each experiment. Additional information on GTLHS setup and operation can be found in our previous publications .…”