Measuring chordae tension during transapical neochordae implantation: Toward understanding objective consequences of mitral valve repair

A geometry-based finite element tool for evaluating mitral valve biomechanics

Mitral valve function depends on its complex geometry and tissue health, with alterations in shape and tissue response affecting the long-term restorarion of function. Previous computational frameworks for biomechanical assessment are mostly based on patient-specific geometries; however, these are not flexible enough to yield a variety of models and assess mitral closure for individually tuned morphological parameters or material property representations. This study details the finite element approach implemented in our previously developed toolbox to assess mitral valve biomechanics and showcases its flexibility through the generation and biomechanical evaluation of different models. A healthy valve geometry was generated and its computational predictions for biomechanics validated against data in the literature. Moreover, two mitral valve models including geometric alterations associated with disease were generated and analysed. The healthy mitral valve model yielded biomechanical predictions in terms of valve closure dynamics, leaflet stresses and papillary muscle and chordae forces comparable to previous computational and experimental studies. Mitral valve function was compromised in geometries representing disease, expressed by the presence of regurgitating areas, elevated stress on the leaflets and unbalanced subvalvular apparatus forces. This showcases the flexibility of the toolbox concerning the generation of a range of mitral valve models with varying geometric definitions and material properties and the evaluation of their biomechanics.

A review of the development of interventional devices for mitral valve repair with the implantation of artificial chords

Mitral regurgitation (MR) was the most common heart valve disease. Surgical repair with artificial chordal replacement had become one of the standard treatments for mitral regurgitation. Expanded polytetrafluoroethylene (ePTFE) was currently the most commonly used artificial chordae material due to its unique physicochemical and biocompatible properties. Interventional artificial chordal implantation techniques had emerged as an alternative treatment option for physicians and patients in treating mitral regurgitation. Using either a transapical or a transcatheter approach with interventional devices, a chordal replacement could be performed transcatheter in the beating heart without cardiopulmonary bypass, and the acute effect on the resolution of mitral regurgitation could be monitored in real-time by transesophageal echo imaging during the procedure. Despite the in vitro durability of the expanded polytetrafluoroethylene material, artificial chordal rupture occasionally occurred. In this article, we reviewed the development and therapeutic results of interventional devices for chordal implantation and discuss the possible clinical factors responsible for the rupture of the artificial chordal material.

Utilization of Engineering Advances for Detailed Biomechanical Characterization of the Mitral-Ventricular Relationship to Optimize Repair Strategies: A Comprehensive Review

The geometrical details and biomechanical relationships of the mitral valve-left ventricular apparatus are very complex and have posed as an area of research interest for decades. These characteristics play a major role in identifying and perfecting the optimal approaches to treat diseases of this system when the restoration of biomechanical and mechano-biological conditions becomes the main target. Over the years, engineering approaches have helped to revolutionize the field in this regard. Furthermore, advanced modelling modalities have contributed greatly to the development of novel devices and less invasive strategies. This article provides an overview and narrative of the evolution of mitral valve therapy with special focus on two diseases frequently encountered by cardiac surgeons and interventional cardiologists: ischemic and degenerative mitral regurgitation.

Optimization Strategies Used for Boosting Piezoelectric Response of Biosensor Based on Flexible Micro-ZnO Composites

Piezoelectric ZnO-based composites have been explored as a flexible and compact sensor for the implantable biomedical systems used in cardio surgery. In this work, a progressive development route was investigated to enhance the performance of piezoelectric composites incorporated with different shape, concentration and connectivity of ZnO fillers. ZnO microrods (MRs) have been successfully synthesized homogeneously in aqueous solution using a novel process-based on chemical bath deposition (CBD) method. The morphological analysis along with Raman scattering and cathodoluminescence spectroscopy of ZnO MRs confirm their high crystalline quality, their orientation along the polar c-axis and the presence of hydrogen-related defects acting as shallow donors in their center. The experimental characterizations highlight that ZnO MR-based composites, with a higher aspect ratio (AR), lead to a significant improvement in the mechanical, dielectric and piezoelectric properties as opposed to the ZnO microparticles (MP) counterparts. The dielectrophoretic (DEP) process is then subjected to both ZnO MP- and MR-based composites, whose performance is expected to be improved as compared to the randomly dispersed composites, thanks to the creation of chain-like structures along the electric field direction. Furthermore, a numerical simulation using COMSOL software is developed to evaluate the influence of the material structuration as well as the filler’s shape on the electric field distribution within different phases (filler, matrix and interface) of the composites. Finally, the aligned MR piezoelectric composites are revealed to be high potential in the development of innovative compact and biocompatible force-sensing devices. Such a technological breakthrough allows the achievement of a real-time precise characterization of mitral valve (MV) coaptation to assist surgeons during MV repair surgery.

Actual perspective on off-pump transapical artificial chord implantation

Mitral valve repair (MVR) is undisputedly associated with better clinical and functional outcomes than any other type of valve substitute. Conventional mitral valve surgery in dedicated high-volume centers can assure excellent results in terms of mortality and freedom from mitral regurgitation (MR) recurrence but requires cardiopulmonary bypass (CPB) and cardioplegic heart arrest. Trying to replicate the percentage of success of surgical MVR is the aim of all new transcatheter mitral dedicated devices. In particular, transapical beating-heart mitral valve repair by artificial chordae implantation with transesophageal echocardiography guidance is an expanding field. The safety and feasibility of the procedure have already been largely demonstrated with Neochord and more recently with Harpoon systems. Wang et al. present the outcomes of the first-in-human experience using a novel artificial chordae implantation device, the Mitralstitch system. Despite a quite small cohort of only 10 patients treated, 1-year results are satisfying and comparable with the early experience with former devices (4 patients with moderate or more MR recurrence). The comparison with surgical MVR is still unfavorable and requires further studies and significant procedure improvement. However, the device permits the treatment of anterior and posterior leaflets prolapse and performs quite easily edge-to-edge reparation. It will be interesting to evaluate longer follow-up in larger cohorts of patients as well as the possibility to shift to the transfemoral approach.

Mitral Valve Prolapse Induces Regionalized Myocardial Fibrosis

Background Mitral valve prolapse (MVP) is one of the most common forms of cardiac valve disease and affects 2% to 3% of the population. Previous imaging reports have indicated that myocardial fibrosis is common in MVP and described its association with sudden cardiac death. These data combined with evidence for postrepair ventricular dysfunction in surgical patients with MVP support a link between fibrosis and MVP. Methods and Results We performed histopathologic analysis of left ventricular (LV) biopsies from peripapillary regions, inferobasal LV wall and apex on surgical patients with MVP, as well as in a mouse model of human MVP (Dzip1S14R/+). Tension-dependent molecular pathways were subsequently assessed using both computational modeling and cyclical stretch of primary human cardiac fibroblasts in vitro. Histopathology of LV biopsies revealed regionalized fibrosis in the peripapillary myocardium that correlated with increased macrophages and myofibroblasts. The MVP mouse model exhibited similar regional increases in collagen deposition that progress over time. As observed in the patient biopsies, increased macrophages and myofibroblasts were observed in fibrotic areas within the murine heart. Computational modeling revealed tension-dependent profibrotic cellular and molecular responses consistent with fibrosis locations related to valve-induced stress. These simulations also identified mechanosensing primary cilia as involved in profibrotic pathways, which was validated in vitro and in human biopsies. Finally, in vitro stretching of primary human cardiac fibroblasts showed that stretch directly activates profibrotic pathways and increases extracellular matrix protein production. Conclusions The presence of prominent regional LV fibrosis in patients and mice with MVP supports a relationship between MVP and progressive damaging effects on LV structure before overt alterations in cardiac function. The regionalized molecular and cellular changes suggest a reactive response of the papillary and inferobasal myocardium to increased chordal tension from a prolapsing valve. These studies raise the question whether surgical intervention on patients with MVP should occur earlier than indicated by current guidelines to prevent advanced LV fibrosis and potentially reduce residual risk of LV dysfunction and sudden cardiac death.

Review of transapical off-pump mitral valve intervention with NeoChord implantation

PURPOSE OF REVIEW

Mitral valve repair surgery has recently shifted from resection-based techniques to leaflet sparing approaches using synthetic neochordae. This has facilitated the growth of a new strategy of transapical off-pump mitral valve intervention with neochord implantation.

RECENT FINDINGS

Minimally invasive approaches for mitral valve repair with robotic or video-assisted mini-right anterolateral thoracotomy have been developed to mitigate the morbidity associated with conventional median sternotomy. Recently, an alternative, less invasive surgical strategy has emerged. This transapical off-pump technique employs the NeoChord DS1000 (NeoChord, Inc., Minneapolis, MN, USA) system to achieve repair with neochordae via a left minithoracotomy incision. With appropriate patient selection, advanced cardiac imaging, and training in device deployment are important for procedural success.

SUMMARY

Early results suggest that transapical off-pump mitral valve intervention with NeoChord implantation is a safe procedure with favorable outcomes for select patients with degenerative mitral regurgitation. Continued experience and clinical trials will assess the potential of this minimally invasive strategy, but this technique is likely to become part of the surgical repertoire for managing chronic degenerative mitral valve disease.

Transapical off-pump mitral valve repair with NeoChord implantation: A systematic review

INTRODUCTION

Mitral valve repair (MVr) is the gold standard for the treatment of degenerative mitral valve regurgitation (MR). The recently introduced NeoChord DS1000 has gained increasing recognition as a feasible, potentially safe, and effective procedure with minor complications and promising outcomes. This study aims to conduct a systematic review of the published literature that discusses the technical feasibility and outcome of transapical off-pump MVr with NeoChord DS1000 device implantation in the treatment of degenerative MR.

METHODS

This review was performed according to the PRISMA statement. Databases searched in this review included Pubmed, Web of Science, Scopus, and Cochrane databases for systematic reviews. All English articles on humans reporting isolated MVr using NeoChord DS1000 device were included provided that basic preoperative data, operative specifications, and postoperative mortality and morbidity were reported.

RESULTS

This review included six studies comprised 249 patients who had NeoChord mitral procedure. Almost all patients included had severe MR (243/249, 97.6%). Operative success was achieved in 241 out of the 249 patients (96.8%). No intraoperative mortality was reported. Intraoperative arrhythmia was reported in six patients (2.4%) and significant bleeding was reported in eight patients (3.2%).

CONCLUSION

Awaiting more evidence, NeoChord mitral procedure appears to be a promising procedure that can be considered in selected cases.

Transseptal chordal replacement: early experience

Chordal replacement is a fundamental technique used in the surgical repair of primary mitral regurgitation, and can be an effective means of preserving the native valve without leaflet resection. Surgical chordal replacement can be challenging since it is performed on an open, non-beating heart, and choosing the correct chord length to restore the zone of coaptation requires both intuition and skill. Developing transcatheter, transfemoral, and transseptal approaches to mitral valve chordal replacement presents the opportunity for safer and potentially earlier treatment of patients with primary mitral regurgitation. In particular, transcatheter methods will allow adjustment of chordal length and position real-time on a beating heart under echocardiographic guidance. In this manuscript, we review the current transcatheter transseptal technologies in development and discuss the various issues related to device design, efficacy, durability, and clinical trial design.

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.

Mitral valve repair based on intraoperative objective measurement

In this paper, we propose a very innovative designed system that enables optimal length adjustment during transapical neochordae implantation for mitral valve repair, increasing accuracy and reproducibility of neochordae length adjustment. Also, such a new device allowed real-time measurement and recording of chordae tension, producing original physiological data. To the best of our knowledge, the tension of chordae had never been measured previously as precisely, especially in in vivo human clinical trials. Preliminary experimental data have been collected on 10 selected patients, giving us the opportunity to assess for the first time the tension applied on the chordae implanted in beating human hearts. The final goal of our measuring device is to provide reliable objective intraoperative data to improve the understanding of changes occurring after mitral valve repair (MVR). This novel measuring instrument may bring change in the paradigm of MVR by allowing repair with strong objective and quantitative, instead of qualitative anatomical analysis.