Computational Modeling of the Subject-Specific Effects of Annuloplasty Ring Sizing on the Mitral Valve to Repair Functional Mitral Regurgitation.

Surgical repair of functional mitral regurgitation (FMR) that occurs in nearly 60% of heart failure (HF) patients is currently performed with undersizing mitral annuloplasty (UMA), which lacks short- and long-term durability. Heterogeneity in valve geometry makes tailoring this repair to each patient challenging, and predictive models that can help with planning this surgery are lacking. In this study, we present a 3D echo-derived computational model, to enable subject-specific, pre-surgical planning of the repair. Three computational models of the mitral valve were created from 3D echo data obtained in three pigs with HF and FMR. An annuloplasty ring model in seven sizes was created, each ring was deployed, and post-repair valve closure was simulated. The results indicate that large annuloplasty rings (> 32 mm) were not effective in eliminating regurgitant gaps nor in restoring leaflet coaptation or reducing leaflet stresses and chordal tension. Smaller rings (≤ 32 mm) restored better systolic valve closure in all investigated cases,but excessive valve tethering and restricted motion of the leaflets were still present. This computational study demonstrates that for effective correction of FMR, the extent of annular reduction differs between subjects, and overly reducing the annulus has deleterious effects on the valve.

Patient-Specific Three-Dimensional Ultrasound Derived Computational Modeling of the Mitral Valve.

Several new techniques to repair the mitral valve affected by functional mitral regurgitation are in development. However, due to the heterogeneity of valve lesions between patients, predicting the outcomes of novel treatment approaches is challenging. We present a patient-specific, 3D ultrasound-derived computational model of the mitral valve for procedure planning, that faithfully mimics the pathological valve dynamics. 3D ultrasound images were obtained in three pigs induced with heart failure and which developed functional mitral regurgitation. For each case, images were segmented, and finite element model of mitral valve was constructed. Annular and papillary muscle dynamics were extracted and imposed as kinematic boundary conditions, and the chordae were pre-strained to induce valve tethering. Valve closure was simulated by applying physiologic transvalvular pressure on the leaflets. Agreement between simulation results and truth datasets was confirmed, with accurate location of regurgitation jets and coaptation defects. Inclusion of kinematic patient-specific boundary conditions was necessary to achieve these results, whereas use of idealized boundary conditions deviated from the truth dataset. Due to the impact of boundary conditions on the model, the effect of repair strategies on valve closure varied as well, indicating that our approach of using patient-specific boundary conditions for mitral valve modeling is valid.

Mitral Butterfly: Preclinical Experience of a Novel Chordal Repair Device Using an Artificial Papillary Muscle.

Transcatheter mitral repair is based on the principle of artificial monochordal repair. In this paper, the authors show an alternative, based on the realization of an artificial papillary muscle concept that avoids multiple chordal replacements and fixation in the myocardium. Unlike the interposition of artificial chordae between the free edge of the leaflet and the myocardium, the so-called Mitral Butterfly device collects a multitude of chordae in a matrix connected to a swing arm, stabilizing prolapsing forces with a broad atrial support. Device testing in chronic animal models and in silico substantiated the underlying device concept and performance after 90 days.

Numerical simulation of transapical off-pump mitral valve repair with neochordae implantation.

BACKGROUND: Transapical off-pump mitral valve (MV) repair is a novel minimally-invasive surgical technique, allowing to correct mitral regurgitation (MR) caused by chordae tendineae rupture. While numerical simulation of the MV structure has proven to be useful to evaluate the effects of the MV surgical repair techniques, no numerical simulation studies on the outcomes of transapical MV repair have been done up to now. OBJECTIVE: The purpose of this study is to evaluate the transapical MV repair using finite element modeling and to determine the effect of the neochordal length on the function of the prolapsing MV. METHODS: The reconstruction of the MV geometry based on the patient-specific data was performed. In order to simulate prolapse, chordae inserted into the middle segment of the posterior leaflet (P2) were ruptured. A total of four virtual transapical repairs using neochordae of different length were performed. The function of the MV before and after virtual repairs was simulated. RESULTS: The evaluation of the effect of the neochordal length on post-repair MV function showed that the length of the implanted neochordae has a significant impact on the correction of MR caused by chordae tendineae rupture. CONCLUSIONS: The presented results can improve the understanding of the effects of transapical MV repair.