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

The Impact of Biomedical Engineering on the Development of Minimally Invasive Cardio-Thoracic Surgery

(1) We describe the boundary conditions for minimally invasive cardiac surgery (MICS) with the aim to reduce procedure-related patient injury and discomfort. (2) The analysis of the MICS work process and its demand for improved tools and devices is followed by a description of the relevant sub-specialties of bio-medical engineering: electronics, biomechanics, and materials sciences. (3) Innovations can represent a desired adaptation of an existing work process or a radical redesign of procedure and devices such as in transcutaneous procedures. Focused interaction between engineers, industry, and surgeons is always mandatory (i.e., a therapeutic alliance for addressing 'unmet patient or professional needs'. (4) Novel techniques in MICS lean heavily on usability and safe and effective use in dedicated hands. Therefore, the use of training and simulation models should enable skills selection, a safe learning curve, and maintenance of proficiency. (5) The critical technical steps and cost-benefit trade-offs during the journey from invention to application will be explained. Business considerations such as time-to-market and returns on investment do shape the cost-benefit room for commercial use of technology. Proof of clinical safety and effectiveness by physicians remains important, but establishing the technical reliability of MICS tools and warranting appropriate surgical skills come first.

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.

Computer simulations of transapical mitral valve repair with neochordae implantation: Clinical implications

OBJECTIVES

Transapical beating heart neochordae implantation is an innovative mitral valve repair technique that has demonstrated promising clinical results in patients with primary mitral regurgitation. However, as clinical experience continues to increase, neochordae implantation criteria have not been fully standardized. The aim of this study was to investigate the biomechanical effects of selecting an antero-lateral apical access site compared with a postero-lateral site, and suboptimal neochordae length compared with optimal suture length, on restoring physiologic left heart dynamics.

METHODS

Transapical neochordae implantation using 3 and 4 sutures was computer simulated under 3 posterior mitral leaflet prolapse conditions: isolated P2, multiscallop P2/P3 and multiscallop P2/P1. Physiologic, pre- and postrepair left heart dynamics were evaluated using a fluid-structure interaction modeling framework.

RESULTS

Despite the absence of residual mitral regurgitation in all postrepair models with optimal neochordae length, selecting an antero-lateral apical entry site for the treatment of P2/P3 prolapse generated a significant increase (>80%) in neochordae tension and P2 peak stress, with respect to a postero-lateral entry site. During isolated P2 prolapse repair, although neochordae overtension by 5% led to minimal hemodynamic changes in the regurgitant volume compared with using an optimal suture length, a significant increase in systolic and diastolic neochordae tension (>300%) and posterior leaflet average stress (70%-460%) was quantified. On the other hand, neochordae undertension by 5% led to worsening of regurgitation severity.

CONCLUSIONS

This parametric computer study represents a further step toward an improved understanding of the biomechanical outcomes of transapical neochordae technologies.

Transapical mitral valve repair with neochordae implantation: FSI analysis of neochordae number and complexity of leaflet prolapse

Transapical mitral valve repair with neochordae implantation is a relatively new minimally invasive technique to treat primary mitral regurgitation. Quantifying the complex biomechanical interaction and interdependence between the left heart structures and the neochordae during this procedure is technically challenging. The aim of this parametric computational study is to investigate the immediate effects of neochordae number and complexity of leaflet prolapse on restoring physiologic left heart dynamics after optimal transapical neochordae repair procedures. Neochordae implantation using three and four sutures was modeled under three clinically relevant prolapse conditions: isolated P2, multi-scallop P2/P3, and multi-scallop P2/P1. A fluid-structure interaction (FSI) modeling framework was used to evaluate the left heart dynamics under baseline, prerepair, and postrepair states. Despite immediate restoration of leaflet coaptation and no residual mitral regurgitation in all postrepair models, the average and peak stresses in the repaired scallop(s) increased >40% and >100%, respectively, compared with the baseline state. Additionally, anterior mitral leaflet marginal chordae tension increased >30%, while posterior mitral leaflet chordae tension decreased at least 30%. No marked differences in hemodynamic performance, in native and neochordae forces, and in leaflet stress were found when implanting three or four sutures. We report, to our knowledge, the first set of time-dependent in silico FSI human neochordae tension measurements during transapical neochordae repair. This work represents a further step towards an improved understanding of the biomechanical outcomes of minimally invasive mitral valve repair procedures.