Optimizing Epicardial Restraint and Reinforcement Following Myocardial Infarction: Moving Towards Localized, Biomimetic, and Multitherapeutic Options

Customizable patterned membranes for cardiac tissue engineering: A model-assisted design method

Myocardial infarction can cause irreversible damage to the heart muscle, which can lead to heart failure. The difficulty of the treatment mainly arises from the anisotropic behavior of the myocardium fibrous structure. Patches or cardiac restraint devices appear to be a promising approach to post-infarction treatment. In this study, we propose a new model-assisted method to design patterned membranes. The proposed approach combines computer experiments and statistical models to optimize the design parameters and to meet the requirement for the post-infarction treatment. Finite element model, global sensitivity analysis, random forest model and response surface model are the key components of the strategy implemented in this study, which is applied to design a real membrane. The metamodel-based design method is able to estimate the equivalent Young's modulus of the membrane in a few seconds and optimization results have been validated a posteriori by laboratory measurements. This solution opens up new prospects for the design of customized membranes with technical specifications tailored to each patient.

Sequential delivery of cardioactive drugs via microcapped microneedle patches for improved heart function in post myocardial infarction rats

After myocardial infarction, the heart undergoes adverse remodeling characterized by a series of pathological changes, including inflammation, apoptosis, fibrosis, and hypertrophy. In addition to cardiac catheter-based re-establishment of blood flow, patients typically receive multiple medications that aim to address these different mechanisms underlying left ventricular remodeling. The current study aims to establish a versatile multi-drug delivery platform for the controlled and sequential delivery of multiple therapeutic agents in a single treatment. Toward this goal, we generated a microcapped microneedle patch carrying methylprednisolone, interleukin-10, and vascular endothelial growth factor. In vitro characterization demonstrated a time-sequenced release pattern of these drug: methylprednisolone for the first 3 days, interleukin-10 from day 1 to 15, and vascular endothelial growth factor from day 3 to 25. The therapeutic effects of the microneedle patch were evaluated in a rat model of acute myocardial infarction induced by permanent ligation of left anterior descending coronary artery. Heart function was measured using trans-thoracic echocardiography. Heart inflammation, apoptosis, hypertrophy and angiogenesis were evaluated using histology. Our data indicated that, at 28 days after patch transplantation, animals receiving the microneedle patch with sequential release of these three agents showed reduced inflammation, apoptosis and cardiac hypertrophy compared to the animals receiving control patch without sequential release of these agents, which is associated with the improved angiogenesis and heart function. In conclusion, the microneedle patch can be utilized to deliver multiple therapeutic agents in a controlled and sequential manner that aligns with the pathological phases following myocardial infarction. STATEMENT OF SIGNIFICANCE: The post-myocardial infarction heart remodeling is characterized by a series of pathological events including acute inflammation, apoptosis, fibrosis, cardiac hypertrophy, and depressed heart function. In current clinical practice, multiple procedures and drugs given at different time points are necessary to combat these series of pathological events. In this study, we developed a novel microcapped microneedle patch for the controlled sequential delivery of triple cardioprotective drugs aiming to combat acute inflammation and cardiac hypertrophy, and promote angiogenesis. This study presents a comprehensive therapeutic approach, with the microneedle patch addressing multifaceted pathological processes during post-myocardial infarction left ventricular remodeling. This cardiac drug delivery system has the potential to improve patient treatment by delivering drugs in alignment with the series of time-dependent pathological phases following myocardial infarction, ultimately improving clinical outcomes.

A Heart Rate Matched Patch for Mechano-Chemical Treatment of Myocardial Infarction: Optimal Design and Transspecies Application

After myocardial infarction (MI), ventricular dilation and the microscopic passive stretching of the infarcted border zone is the meaning contributor to the continuous expansion of myocardial fibrosis. Epicardial hydrogel patches have been demonstrated to alleviate this sequela of MI in small-animal models. However, these have not been successfully translated to humans or even large animals, in part because of challenges in attaining both the greater stiffness and slower viscoelastic relaxation that mathematical models predict to be optimal for application to larger, slower-beating hearts. Here, using borate-based dynamic covalent chemistry, we develop an injectable "heart rate matched" viscoelastic gelatin (VGtn) hydrogel with a gel point tunable across the stiffnesses and frequencies that are predicted to transspecies and cross-scale cardiac repair after MI. Small-animal experiments demonstrated that, compared to heart rate mismatched patches, the heart rate matched VGtn patches inhibited ventricular bulging and attenuated stress concentrations in the myocardium after MI. In particular, the viscoelastic patch can coordinate the microscopic strain at the infarction boundary. VGtn loaded with anti-fibrotic agents further reduced myocardial damage and promoted angiogenesis in the myocardium. The tuned heart rate matched patches demonstrated similar benefits in a larger-scale and lower heart rate porcine MI model. Results suggest that heart rate matched VGtn patches may hold potential for clinical translation.

Next-Generation Cardiac Interfacing Technologies Using Nanomaterial-Based Soft Bioelectronics

Cardiac interfacing devices are essential components for the management of cardiovascular diseases, particularly in terms of electrophysiological monitoring and implementation of therapies. However, conventional cardiac devices are typically composed of rigid and bulky materials and thus pose significant challenges for effective long-term interfacing with the curvilinear surface of a dynamically beating heart. In this regard, the recent development of intrinsically soft bioelectronic devices using nanocomposites, which are fabricated by blending conductive nanofillers in polymeric and elastomeric matrices, has shown great promise. The intrinsically soft bioelectronics not only endure the dynamic beating motion of the heart and maintain stable performance but also enable conformal, reliable, and large-area interfacing with the target cardiac tissue, allowing for high-quality electrophysiological mapping, feedback electrical stimulations, and even mechanical assistance. Here, we explore next-generation cardiac interfacing strategies based on soft bioelectronic devices that utilize elastic conductive nanocomposites. We first discuss the conventional cardiac devices used to manage cardiovascular diseases and explain their undesired limitations. Then, we introduce intrinsically soft polymeric materials and mechanical restraint devices utilizing soft polymeric materials. After the discussion of the fabrication and functionalization of conductive nanomaterials, the introduction of intrinsically soft bioelectronics using nanocomposites and their application to cardiac monitoring and feedback therapy follow. Finally, comments on the future prospects of soft bioelectronics for cardiac interfacing technologies are discussed.

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.

Mechanical Characterization of 3D-Printed Patterned Membranes for Cardiac Tissue Engineering: An Experimental and Numerical Study

A myocardial infarction can cause irreversible damage to the heart muscle. A promising approach for the treatment of myocardial infarction and prevention of severe complications is the application of cardiac patches or epicardial restraint devices. The challenge for the fabrication of cardiac patches is the replication of the fibrillar structure of the myocardium, in particular its anisotropy and local elasticity. In this study, we developed a chitosan-gelatin-guar gum-based biomaterial ink that was fabricated using 3D printing to create patterned anisotropic membranes. The experimental results were then used to develop a numerical model able to predict the elastic properties of additional geometries with tunable elasticity that could easily match the mechanical properties of the heart tissue (particularly the myocardium).

Advancements in left ventricular assist devices to prevent pump thrombosis and blood coagulopathy

Mechanical circulatory support (MCS) devices, such as left ventricular assist devices (LVADs) are very useful in improving outcomes in patients with advanced-stage heart failure. Despite recent advances in LVAD development, pump thrombosis is one of the most severe adverse events caused by LVADs. The contact of blood with artificial materials of LVAD pumps and cannulas triggers the coagulation cascade. Heat spots, for example, produced by mechanical bearings are often subjected to thrombus build-up when low-flow situations impair washout and thus the necessary cooling does not happen. The formation of thrombus in an LVAD may compromise its function, causing a drop in flow and pumping power leading to failure of the LVAD, if left unattended. If a clot becomes dislodged and circulates in the bloodstream, it may disturb the flow or occlude the blood vessels in vital organs and cause internal damage that could be fatal, for example, ischemic stroke. That is why patients with LVADs are on anti-coagulant medication. However, the anti-coagulants can cause a set of issues for the patient-an example of gastrointestinal (GI) bleeding is given in illustration. On account of this, these devices are only used as a last resort in clinical practice. It is, therefore, necessary to develop devices with better mechanics of blood flow, performance and hemocompatibility. This paper discusses the development of LVADs through landmark clinical trials in detail and describes the evolution of device design to reduce the risk of pump thrombosis and achieve better hemocompatibility. Whilst driveline infection, right heart failure and arrhythmias have been recognised as LVAD-related complications, this paper focuses on complications related to pump thrombosis, especially blood coagulopathy in detail and potential strategies to mitigate this complication. Furthermore, it also discusses the LVAD implantation techniques and their anatomical challenges.

Mitral valve replacement and implantation of an extracardial mesh frame in patients with severe heart failure: results of a clinical study and a description of a clinical case 18 years after surgery

Aim    Dilated cardiomyopathy (DCMP) is a major cause for severe heart failure. Development of a combination (drug and surgery) treatment of this disease is relevant. This prospective observational study was aimed at evaluating short- and long-term results of extracardiac mesh implantation in DCMP patients with heart failure resistant to the optimum drug therapy.Material and methods    The extracardiac mesh ACOR-1 was implanted in 15 patients with DCMP. All meshes were produced individually for each patient and made of Gelweave (great Britain) vascular graft strips. The mesh size corresponded to the heart diastolic size, which was measured after achieving a maximum possible clinical improvement for the patient. Long-term results were followed for up to 4 years. Mean age of patients was 43.1±10.8 years (from 28 to 62 years). One patient was followed up for 18 years. Data of that patient were presented as a clinical case report.Results    From October, 2003 through October, 2007, 15 DCMP patients received mesh implants. Cases of in-hospital death were absent. In 3 mos. after the surgery, left ventricular volumes decreased (end-diastolic volume decreased from 251.7±80.7 to 229.0±61.3 ml; end-systolic volume decreased from 182.3±73.6 to 167.7±46.2 ml), and the left ventricular pump function improved (ejection fraction increased from 25.2±6.0 to 27.1±5.1 %; cardiac index increased from 2.0±0.5 to 2.4±0.7 ml /min /m2). The functional state of patients improved by one NYHA class, from 3.7±0.3 to 2.8±0.6. In some cases, the left ventricular size and the systolic function completely normalized. There were no episodes of circulatory decompensation in the long term after surgery. Actuarial survival for the observation period was 100%.Conclusion    Implantation of extracardiac mesh prevented progression of heart dilatation and, in combination with drug therapy, it may represent an effective method for treatment of DCMP.

Elastomeric cardiopatch scaffold for myocardial repair and ventricular support

OBJECTIVES

Prevention of postischaemic ventricular dilatation progressing towards pathological remodelling is necessary to decrease ventricular wall deterioration. Myocardial tissue engineering may play a therapeutic role due to its capacity to replace the extracellular matrix, thereby creating niches for cell homing. In this experimental animal study, a biomimetic cardiopatch was created with elastomeric scaffolds and nanotechnologies.

METHODS

In an experimental animal study in 18 sheep, a cardiopatch was created with adipose tissue-derived progenitor cells seeded into an engineered bioimplant consisting of 3-dimensional bioabsorbable polycaprolactone scaffolds filled with a peptide hydrogel (PuraMatrix™). This patch was then transplanted to cover infarcted myocardium. Non-absorbable poly(ethyl) acrylate polymer scaffolds were used as controls.

RESULTS

Fifteen sheep were followed with ultrasound scans at 6 months, including echocardiography scans, tissue Doppler and spectral flow analysis and speckle-tracking imaging, which showed a reduction in longitudinal left ventricular deformation in the cardiopatch-treated group. Magnetic resonance imaging (late gadolinium enhancement) showed reduction of infarct size relative to left ventricular mass in the cardiopatch group versus the controls. Histopathological analysis at 6 months showed that the cardiopatch was fully anchored and integrated to the infarct area with minimal fibrosis interface, thereby promoting angiogenesis and migration of adipose tissue-derived progenitor cells to surrounding tissues.

CONCLUSIONS

This study shows the feasibility and effectiveness of a cardiopatch grafted onto myocardial infarction scars in an experimental animal model. This treatment decreased fibrosis, limited infarct scar expansion and reduced postischaemic ventricular deformity. A capillary network developed between our scaffold and the heart. The elastomeric cardiopatch seems to have a positive impact on ventricular remodelling and performance in patients with heart failure.

Soft Robotics

In Nature, the adaptability of many organisms and their capability to survive in challenging and dynamically changing environments are closely linked to their characteristics and the morphology of their body parts [...].