Mechanical effects of MitraClip on leaflet stress and myocardial strain in functional mitral regurgitation - A finite element modeling study

Simulated Effects of Acute Left Ventricular Myocardial Infarction on Mitral Regurgitation in an Ovine Model

Ischemic mitral regurgitation (IMR) occurs from incomplete coaptation of the mitral valve (MV) after myocardial infarction (MI), typically worsened by continued remodeling of the left ventricular (LV). The importance of LV remodeling is clear as IMR is induced by the post-MI dual mechanisms of mitral annular dilation and leaflet tethering from papillary muscle (PM) distension via the MV chordae tendineae (MVCT). However, the detailed etiology of IMR remains poorly understood, in large part due to the complex interactions of the MV and the post-MI LV remodeling processes. Given the patient-specific anatomical complexities of the IMR disease processes, simulation-based approaches represent an ideal approach to improve our understanding of this deadly disease. However, development of patient-specific models of left ventricle-mitral valve (LV-MV) interactions in IMR are complicated by the substantial variability and complexity of the MR etiology itself, making it difficult to extract underlying mechanisms from clinical data alone. To address these shortcomings, we developed a detailed ovine LV-MV finite element (FE) model based on extant comprehensive ovine experimental data. First, an extant ovine LV FE model (Sci. Rep. 2021 Jun 29;11(1):13466) was extended to incorporate the MV using a high fidelity ovine in vivo derived MV leaflet geometry. As it is not currently possible to image the MVCT in vivo, a functionally equivalent MVCT network was developed to create the final LV-MV model. Interestingly, in pilot studies, the MV leaflet strains did not agree well with known in vivo MV leaflet strain fields. We then incorporated previously reported MV leaflet prestrains (J. Biomech. Eng. 2023 Nov 1;145(11):111002) in the simulations. The resulting LV-MV model produced excellent agreement with the known in vivo ovine MV leaflet strains and deformed shapes in the normal state. We then simulated the effects of regional acute infarctions of varying sizes and anatomical locations by shutting down the local myocardial contractility. The remaining healthy (noninfarcted) myocardium mechanical behaviors were maintained, but allowed to adjust their active contractile patterns to maintain the prescribed pressure-volume loop behaviors in the acute post-MI state. For all cases studied, the LV-MV simulation demonstrated excellent agreement with known LV and MV in vivo strains and MV regurgitation orifice areas. Infarct location was shown to play a critical role in resultant MV leaflet strain fields. Specifically, extensional deformations of the posterior leaflets occurred in the posterobasal and laterobasal infarcts, while compressive deformations of the anterior leaflet were observed in the anterobasal infarct. Moreover, the simulated posterobasal infarct induced the largest MV regurgitation orifice area, consistent with experimental observations. The present study is the first detailed LV-MV simulation that reveals the important role of MV leaflet prestrain and functionally equivalent MVCT for accurate predictions of LV-MV interactions. Importantly, the current study further underscored simulation-based methods in understanding MV function as an integral part of the LV.

Looking towards the future: patient-specific computational modeling to optimize outcomes for transcatheter mitral valve repair

Severe mitral valve regurgitation (MR) is a heart valve disease that progresses to end-stage congestive heart failure and death if left untreated. Surgical repair or replacement of the mitral valve (MV) remains the gold standard for treatment of severe MR, with repair techniques aiming to restore the native geometry of the MV. However, patients with extensive co-morbidities may be ineligible for surgical intervention. With the emergence of transcatheter MV repair (TMVR) treatment paradigms for MR will evolve. The longer-term outcomes of TMVR and its effectiveness compared to surgical repair remain unknown given the differing patient eligibility for either treatment at this time. Advances in computational modeling will elucidate answers to these questions, employing techniques such as finite element method and fluid structure interactions. Use of clinical imaging will permit patient-specific MV models to be created with high accuracy and replicate MV pathophysiology. It is anticipated that TMVR technology will gradually expand to treat lower-risk patient groups, thus pre-procedural computational modeling will play a crucial role guiding clinicians towards the optimal intervention. Additionally, concerted efforts to create MV models will establish atlases of pathologies and biomechanics profiles which could delineate which patient populations would best benefit from specific surgical vs. TMVR options. In this review, we describe recent literature on MV computational modeling, its relevance to MV repair techniques, and future directions for translational application of computational modeling for treatment of MR.

Recurrent mitral regurgitation with haemolytic anaemia after MitraClip procedure: an autopsy case report

Background

Transcatheter edge-to-edge mitral valve repair (TMVr) has been developed as an alternative therapeutic approach to patients with severe mitral regurgitation (MR) at high-surgical risks. Single leaflet device attachment (SLDA) is a well-known complication after the TMVr procedure, while an autopsy case experiencing haemolytic anaemia has been scarcely reported.

Case summary

A 79-year-old woman presented with New York Heart Association Class 3 congestive heart failure due to severe MR. The Heart Team planned TMVr using the MitraClip considering a high-surgical risk due to the history of open-chest surgery. The procedure was successful with two clips and a significant reduction of MR was confirmed. On the 12th day after the procedure, congestive heart failure was worsened and a transthoracic echocardiogram revealed severe MR suggestive of SLDA. Blood test showed normocytic anaemia with serum lactate dehydrogenase level elevation and renal function deterioration. We diagnosed as mechanical haemolysis induced by recurrent MR because of a decrease in serum haptoglobin level and the presence of schizocyte in the blood smear. Despite our intensive medical treatment, she died on the 119th day after the procedure. The pathological autopsy demonstrated that the ruptured leaflet was thickened with layered structure and severe fibrosis, while there were no findings of calcification, vegetations, or abscesses.

Discussion

Single leaflet device attachment and subsequent mechanical haemolysis are rare but fatal complications after TMVr with the MitraClip. Not only degenerative MR but also functional MR may be associated with valve leaflet degeneration. A possibility of mechanical haemolysis should be considered when recurrent MR is observed after TMVr.

A Simulation Study of the Effects of Number and Location of MitraClips on Mitral Regurgitation

Background

MitraClip (MC) is a device that is implanted on the mitral valve (MV) percutaneously to treat severe mitral regurgitation (MR). It is common practice to place the MCs at the site of the most significant MR jets identified by echocardiography.

Objectives

We used computational modeling to examine changes in MR after MC placement.

Methods

Echocardiographic images from 29 patients with MR were analyzed to reconstruct geometries for finite element simulations and created fluid structure interaction models of the MV with deformable hyperelastic material, the left ventricle as the surrounding geometry, and blood flow. Blood flow was modelled with smoothed particle hydrodynamics. The number of blood particles on the atrial side of MV was used to estimate MR. MC placement was based on the MR jets (jet-based strategy using primary and secondary jets) and simulation models using various MCs locations.

Results

Computational modelling was able to quantitate reductions in MR after MC placement. Reduction in MR was related to the number of MCs used: 42% reduction with 1 MC, 62% with 2 MCs, and 88% with 3 MCs. Using 2 MCs did not always result in an MR reduction greater than with a single MC. In 31% (9 of 29) of patients, the jet-based strategy did not lead to maximum MR reduction. The majority of patients (89%) who did not have maximal MR reduction with the MC placement using the jet-based strategy, had wide jets, and/or had multiple jets.

Conclusions

Subject-specific simulation models may be helpful to identify optimal locations for MC placement in patients with MR.

Mitral Valve Atlas for Artificial Intelligence Predictions of MitraClip Intervention Outcomes

Severe mitral regurgitation (MR) is a cardiac disease that can lead to fatal consequences. MitraClip (MC) intervention is a percutaneous procedure whereby the mitral valve (MV) leaflets are connected along the edge using MCs. The outcomes of the MC intervention are not known in advance, i.e., the outcomes are quite variable. Artificial intelligence (AI) can be used to guide the cardiologist in selecting optimal MC scenarios. In this study, we describe an atlas of shapes as well as different scenarios for MC implantation for such an AI analysis. We generated the MV geometrical data from three different sources. First, the patients' 3-dimensional echo images were used. The pixel data from six key points were obtained from three views of the echo images. Using PyGem, an open-source morphing library in Python, these coordinates were used to create the geometry by morphing a template geometry. Second, the dimensions of the MV, from the literature were used to create data. Third, we used machine learning methods, principal component analysis, and generative adversarial networks to generate more shapes. We used the finite element (FE) software ABAQUS to simulate smoothed particle hydrodynamics in different scenarios for MC intervention. The MR and stresses in the leaflets were post-processed. Our physics-based FE models simulated the outcomes of MC intervention for different scenarios. The MR and stresses in the leaflets were computed by the FE models for a single clip at different locations as well as two and three clips. Results from FE simulations showed that the location and number of MCs affect subsequent residual MR, and that leaflet stresses do not follow a simple pattern. Furthermore, FE models need several hours to provide the results, and they are not applicable for clinical usage where the predicted outcomes of MC therapy are needed in real-time. In this study, we generated the required dataset for the AI models which can provide the results in a matter of seconds.

A finite element model of the cardiac ventricles with coupled circulation: Biventricular mesh generation with hexahedral elements, airbags and a functional mockup interface to the circulation

INTRODUCTION

Finite element (FE) mechanics models of the heart are becoming more sophisticated. However, there is lack of consensus about optimal element type and coupling of FE models to the circulation. We describe biventricular (left (LV) and right (RV) ventricles) FE mechanics model creation using hexahedral elements, airbags and a functional mockup interface (FMI) to lumped-parameter models of the circulation.

METHODS

Cardiac MRI (CMR) was performed in two healthy volunteers and a single patient with ischemic heart disease (IHD). CMR images were segmented and surfaced, meshing with hexahedral elements was performed with a "thin butterfly with septum" topology. LV and RV inflow and outflow airbags were coupled to lumped-parameter circulation models with an FMI interface. Pulmonary constriction (PAC) and vena cava occlusion (VCO) were simulated and end-systolic pressure-volume relations (ESPVR) were calculated.

RESULTS

Mesh construction was prompt with representative contouring and mesh adjustment requiring 32 and 26 min Respectively. The numbers of elements ranged from 4104 to 5184 with a representative Jacobian of 1.0026 ± 0.4531. Agreement between CMR-based surfaces and mesh was excellent with root-mean-squared error of 0.589 ± 0.321 mm. The LV ESPVR slope was 3.37 ± 0.09 in volunteers but 2.74 in the IHD patient. The effect of PAC and VCO on LV ESPVR was consistent with ventricular interaction (p = 0.0286).

CONCLUSION

Successful co-simulation using a biventricular FE mechanics model with hexahedral elements, airbags and an FMI interface to lumped-parameter model of the circulation was demonstrated. Future studies will include comparison of element type and study of cardiovascular pathologies and device therapies.

Transcatheter Mitral Valve Repair to Treat Postmyocardial Infarction Papillary Muscle Rupture

A 75-year-old man was admitted to the emergency department for a late-presenting myocardial infarction. The coronary angiography revealed a thrombotic occlusion of the circumflex artery. He presented a rapid hemodynamic and respiratory deterioration as a result of a severe mitral regurgitation with a flail anterior leaflet due to a partial tear of the medial papillary muscle (PM). Given the patient's comorbidities, a percutaneous mitral valve repair with two-dimensional (2D)/3D transesophageal echocardiography was performed, deploying two MitraClips. MitraClip implantation may be considered in an acute setting of PM tear as an alternative for surgical treatment in selected patients.

State-of-the-art intra-procedural imaging for the mitral and tricuspid PASCAL Repair System

Advanced intra-procedural imaging techniques have been integral to technical and procedural success transcatheter devices. A novel leaflet approximation therapy, the PASCAL Transcatheter Valve Repair System (Edwards Lifesciences, Irvine, CA, USA) has demonstrated high procedural success, acceptable safety, and significant clinical improvement in patients with severe mitral and tricuspid regurgitation and has CE mark approval in Europe with pivotal trials underway in the USA. This review outlines the pre-procedural imaging views and advanced transoesophageal imaging protocols both mitral and tricuspid valve device implantation.

Impact of preexisting coronary arterial disease in patients undergoing percutaneous mitral valve repair (MitraClip)

INTRODUCTION

Percutaneous mitral valve repair with Mitraclip device has been approved for the treatment of symptomatic mitral valve regurgitation in patients deemed high surgical risk. It's unclear whether the presence of preexisting coronary arterial disease (CAD) affects the postprocedural outcomes of Mitraclip.

METHODS

The study population was extracted from the 2016 Nationwide Readmissions Data (NRD) using the International Classification of Diseases, Tenth Revision, Clinical Modifications/Procedure Coding System (ICD-10-CM/PCS) for Mitraclip, preexisting CAD, and postprocedural complications. Study primary endpoints included in-hospital all-cause mortality, cardiogenic shock, acute myocardial infarction (AMI), acute kidney injury (AKI), stroke, acute respiratory failure, length of hospital stay (LOS), and 30-day readmission rate.

RESULTS

A total of 2,539 discharges that had Mitraclip during the index hospitalization, 62.3% had history of preexisting CAD. Mean age was 78.5 years and 46.6% were female. Overall, the presence of preexisting CAD was associated with higher AMI (1.6 vs. 0.4%, p < .01), however, there was no significant differences in terms of in-hospital all-cause mortality (2.2 vs. 2.6%, p = .52), cardiogenic shock (3.4 vs. 4.1%, p = .39), AKI (14.7 vs. 13.6%, p = .43), stroke (0.9 vs. 0.5%, p = .31), acute respiratory failure (9.7 vs. 8.8%, p = .43), LOS (5.3 vs. 5.3 days, p = .85) or 30-day readmission rate (14.6 vs. 14.4%, p = .92). These results persisted after adjustment for baseline characteristics. The subgroup of CAD patients who received percutaneous coronary intervention (PCI) was associated with higher in-hospital mortality (22.5 vs. 2.0%, p < .01), cardiogenic shock (25.0 vs. 3.3%, p < .01), AMI (22.5 vs. 0.8%, p < .01), AKI (55.0 vs. 13.7%, p < .01), stroke (10.0 vs. 0.6%, p < .01), acute respiratory failure (45.0 vs. 8.8%, p < .01), and longer LOS (21.5 vs. 5.1 days, p < .01), however there was no significant difference in 30-day readmission rate (15.0 vs. 14.5%, p = .95).

CONCLUSIONS

Preexisting CAD was associated with higher in-hospital AMI post-Mitraclip but with comparable mortality and other morbidities. Patients who received PCI during the same index hospitalization had higher in-hospital mortality and morbidity.

Precision medicine in human heart modeling : Perspectives, challenges, and opportunities

Precision medicine is a new frontier in healthcare that uses scientific methods to customize medical treatment to the individual genes, anatomy, physiology, and lifestyle of each person. In cardiovascular health, precision medicine has emerged as a promising paradigm to enable cost-effective solutions that improve quality of life and reduce mortality rates. However, the exact role in precision medicine for human heart modeling has not yet been fully explored. Here, we discuss the challenges and opportunities for personalized human heart simulations, from diagnosis to device design, treatment planning, and prognosis. With a view toward personalization, we map out the history of anatomic, physical, and constitutive human heart models throughout the past three decades. We illustrate recent human heart modeling in electrophysiology, cardiac mechanics, and fluid dynamics and highlight clinically relevant applications of these models for drug development, pacing lead failure, heart failure, ventricular assist devices, edge-to-edge repair, and annuloplasty. With a view toward translational medicine, we provide a clinical perspective on virtual imaging trials and a regulatory perspective on medical device innovation. We show that precision medicine in human heart modeling does not necessarily require a fully personalized, high-resolution whole heart model with an entire personalized medical history. Instead, we advocate for creating personalized models out of population-based libraries with geometric, biological, physical, and clinical information by morphing between clinical data and medical histories from cohorts of patients using machine learning. We anticipate that this perspective will shape the path toward introducing human heart simulations into precision medicine with the ultimate goals to facilitate clinical decision making, guide treatment planning, and accelerate device design.

A Comprehensive Engineering Analysis of Left Heart Dynamics After MitraClip in a Functional Mitral Regurgitation Patient

Percutaneous edge-to-edge mitral valve (MV) repair using MitraClip has been recently established as a treatment option for patients with heart failure and functional mitral regurgitation (MR), which significantly expands the number of patients that can be treated with this device. This study aimed to quantify the morphologic, hemodynamic and structural changes, and evaluate the biomechanical interaction between the MitraClip and the left heart (LH) complex of a heart failure patient with functional MR using a fluid-structure interaction (FSI) modeling framework. MitraClip implantation using lateral, central and double clip positions, as well as combined annuloplasty procedures were simulated in a patient-specific LH model that integrates detailed anatomic structures, incorporates age- and gender-matched non-linear elastic material properties, and accounts for mitral chordae tethering. Our results showed that antero-posterior distance, mitral annulus spherecity index, anatomic regurgitant orifice area, and anatomic opening orifice area decreased by up to 28, 39, 52, and 71%, respectively, when compared to the pre-clip model. MitraClip implantation immediately decreased the MR severity and improved the hemodynamic profile, but imposed a non-physiologic configuration and loading on the mitral apparatus, with anterior and posterior leaflet stress significantly increasing up to 210 and 145% during diastole, respectively. For this patient case, while implanting a combined central clip and ring resulted in the highest reduction in the regurgitant volume (46%), this configuration also led to mitral stenosis. Patient-specific computer simulations as used here can be a powerful tool to examine the complex device-host biomechanical interaction, and may be useful to guide device positioning for potential favorable clinical outcomes.

Transcatheter MitraClip repair alters mitral annular geometry - device induced annular remodeling on three-dimensional echocardiography predicts therapeutic response

Background

Echocardiography (echo) is widely used to guide therapeutic decision-making for patients being considered for MitraClip. Relative utility of two- (2D) and three-dimensional (3D) echo predictors of MitraClip response, and impact of MitraClip on mitral annular geometry, are uncertain.

Methods

The study population comprised patients with advanced (> moderate) MR undergoing MitraClip. Mitral annular geometry was quantified on pre-procedural 2D transthoracic echocardiography (TTE) and intra-procedural 3D transesophageal echocardiography (TEE); 3D TEE was used to measure MitraClip induced changes in annular geometry. Optimal MitraClip response was defined as ≤mild MR on follow-up (mean 2.7 ± 2.5 months) post-procedure TTE.

Results

Eighty patients with advanced MR underwent MitraClip; 41% had optimal response (≤mild MR). Responders had smaller pre-procedural global left ventricular (LV) end-diastolic size and mitral annular diameter on 2D TTE (both p ≤ 0.01), paralleling smaller annular area and circumference on 3D TEE (both p = 0.001). Mitral annular size yielded good diagnostic performance for optimal MitraClip response (AUC 0.72, p < 0.01). In multivariate analysis, sub-optimal MitraClip response was independently associated with larger pre-procedural mitral annular area on 3D TEE (OR 1.93 per cm²/m² [CI 1.19–3.13], p = 0.007) and global LV end-diastolic volume on 2D TTE (OR 1.29 per 10 ml/m² [CI 1.02–1.63], p = 0.03). Substitution of 2D TTE derived mitral annular diameter for 3D TEE data demonstrated a lesser association between pre-procedural annular size (OR 5.36 per cm/m² [CI 0.95–30.19], p = 0.06) and sub-optimal MitraClip response. Matched pre- and post-procedural TEE analyses demonstrated MitraClip to acutely decrease mitral annular area and circumference (all p < 0.001) as well as mitral tenting height, area, and volume (all p < 0.05): Magnitude of MitraClip induced reductions in mitral annular circumference on intra-procedural 3D TEE was greater among patients with, compared to those without, sub-optimal MitraClip response (>mild MR) on followup TTE (p = 0.017); greater magnitude of device-induced annular reduction remained associated with sub-optimal MitraClip response even when normalized for pre-procedure annular circumference (p = 0.028).

Conclusions

MitraClip alters mitral annular geometry as quantified by intra-procedural 3D TEE. Pre-procedural mitral annular dilation and magnitude of device-induced reduction in mitral annular size on 3D TEE are each associated with sub-optimal therapeutic response to MitraClip.