Direct Cardiac Compression Devices to Augment Heart Biomechanics and Function

The Future of Durable Mechanical Circulatory Support: Emerging Technological Innovations and Considerations to Enable Evolution of the Field

The field of durable mechanical circulatory support (MCS) has undergone an incredible evolution over the past few decades, resulting in significant improvements in longevity and quality of life for patients with advanced heart failure. Despite these successes, substantial opportunities for further improvements remain, including in pump design and ancillary technology, perioperative and postoperative management, and the overall patient experience. Ideally, durable MCS devices would be fully implantable, automatically controlled, and minimize the need for anticoagulation. Reliable and long-term total artificial hearts for biventricular support would be available; and surgical, perioperative, and postoperative management would be informed by the individual patient phenotype along with computational simulations. In this review, we summarize emerging technological innovations in these areas, focusing primarily on innovations in late preclinical or early clinical phases of study. We highlight important considerations that the MCS community of clinicians, engineers, industry partners, and venture capital investors should consider to sustain the evolution of the field.

Preclinical Proof-of-Concept of a Minimally Invasive Direct Cardiac Compression Device for Pediatric Heart Support

PURPOSE

For pediatric patients, extracorporeal membrane oxygenation (ECMO) remains the predominant mechanical circulatory support (MCS) modality for heart failure (HF) although survival to discharge rates remain between 50 and 60% for these patients. The device-blood interface and disruption of physiologic hemodynamics are significant contributors to poor outcomes.

METHODS

In this study, we evaluate the preclinical feasibility of a minimally invasive, non-blood-contacting pediatric DCC prototype for temporary MCS. Proof-of-concept is demonstrated in vivo in an animal model of HF. Hemodynamic pressures and flows were examined.

RESULTS

Minimally invasive deployment on the beating heart was successful without cardiopulmonary bypass or anticoagulation. During HF, device operation resulted in an immediate 43% increase in cardiac output while maintaining pulsatile hemodynamics. Compared to the pre-HF baseline, the device recovered up to 95% of ventricular stroke volume. At the conclusion of the study, the device was easily removed from the beating heart.

CONCLUSIONS

This preclinical proof-of-concept study demonstrated the feasibility of a DCC device on a pediatric scale that is minimally invasive and non-blood contacting, with promising hemodynamic support and durability for the initial intended duration of use. The ability of DCC to maintain pulsatile MCS without blood contact represents an opportunity to mitigate the mortality and morbidity observed in non-pulsatile, blood-contacting MCS.

An image-driven micromechanical approach to characterize multiscale remodeling in infarcted myocardium

Myocardial infarction (MI) is accompanied by the formation of a fibrotic scar in the left ventricle (LV) and initiates significant alterations in the architecture and constituents of the LV free wall (LVFW). Previous studies have shown that LV adaptation is highly individual, indicating that the identification of remodeling mechanisms post-MI demands a fully subject-specific approach that can integrate a host of structural alterations at the fiber-level to changes in bulk biomechanical adaptation at the tissue-level. We present an image-driven micromechanical approach to characterize remodeling, assimilating new biaxial mechanical data, histological studies, and digital image correlation data within an in-silico framework to elucidate the fiber-level remodeling mechanisms that drive tissue-level adaptation for each subject. We found that a progressively diffused collagen fiber structure combined with similarly disorganized myofiber architecture in the healthy region leads to the loss of LVFW anisotropy post-MI, offering an important tissue-level hallmark for LV maladaptation. In contrast, our results suggest that reductions in collagen undulation are an adaptive mechanism competing against LVFW thinning. Additionally, we show that the inclusion of subject-specific geometry when modeling myocardial tissue is essential for accurate prediction of tissue kinematics. Our approach serves as an essential step toward identifying fiber-level remodeling indices that govern the transition of MI to systolic heart failure. These indices complement the traditional, organ-level measures of LV anatomy and function that often fall short of early prognostication of heart failure in MI. In addition, our approach offers an integrated methodology to advance the design of personalized interventions, such as hydrogel injection, to reinforce and suppress native adaptive and maladaptive mechanisms, respectively, to prevent the transition of MI to heart failure. STATEMENT OF SIGNIFICANCE: Biomechanical and architectural adaptation of the LVFW remains a central, yet overlooked, remodeling process post-MI. Our study indicates the biomechanical adaptation of the LVFW post-MI is highly individual and driven by altered fiber network architecture and collective changes in collagen fiber content, undulation, and stiffness. Our findings demonstrate the possibility of using cardiac strains to infer such fiber-level remodeling events through in-silico modeling, paving the way for in-vivo characterization of multiscale biomechanical indices in humans. Such indices will complement the traditional, organ-level measures of LV anatomy and function that often fall short of early prognostication of heart failure in MI.

Artificial Muscles and Soft Robotic Devices for Treatment of End-Stage Heart Failure

Medical soft robotics constitutes a rapidly developing field in the treatment of cardiovascular diseases, with a promising future for millions of patients suffering from heart failure worldwide. Herein, the present state and future direction of artificial muscle-based soft robotic biomedical devices in supporting the inotropic function of the heart are reviewed, focusing on the emerging electrothermally artificial heart muscles (AHMs). Artificial muscle powered soft robotic devices can mimic the action of complex biological systems such as heart compression and twisting. These artificial muscles possess the ability to undergo complex deformations, aiding cardiac function while maintaining a limited weight and use of space. Two very promising candidates for artificial muscles are electrothermally actuated AHMs and biohybrid actuators using living cells or tissue embedded with artificial structures. Electrothermally actuated AHMs have demonstrated superior force generation while creating the prospect for fully soft robotic actuated ventricular assist devices. This review will critically analyze the limitations of currently available devices and discuss opportunities and directions for future research. Last, the properties of the cardiac muscle are reviewed and compared with those of different materials suitable for mechanical cardiac compression.

Advances in novel devices for the treatment of heart failure

Heart failure (HF) is one of the leading causes of global health impairment. Current drugs are still limited in their effectiveness in the treatment and reversal of HF: for example, drugs for acute HF (AHF) help to reduce congestion and relieve symptoms, but they do little to improve survival; most conventional drugs for HF with preserved ejection fraction (HFpEF) do not improve the prognosis; and drugs have extremely limited effects on advanced HF. In recent years, progress in device therapies has bridged this gap to a certain extent. For example, the availability of the left ventricular assist device has brought new options to numerous advanced HF patients. In addition to this recognizable device, a range of promising novel devices with preclinical or clinical trial results are emerging that seek to treat or reverse HF by providing circulatory support, repairing structural abnormalities in the heart, or providing electrical stimulation. These devices may be useful for the treatment of HF. In this review, we summarized recent advances in novel devices for AHF, HFpEF, and HF with reduced ejection fraction (HFrEF) with the aim of providing a reference for clinical treatment and inspiration for novel device development.

Soft robotic patient-specific hydrodynamic model of aortic stenosis and ventricular remodeling

Aortic stenosis (AS) affects about 1.5 million people in the United States and is associated with a 5-year survival rate of 20% if untreated. In these patients, aortic valve replacement is performed to restore adequate hemodynamics and alleviate symptoms. The development of next-generation prosthetic aortic valves seeks to provide enhanced hemodynamic performance, durability, and long-term safety, emphasizing the need for high-fidelity testing platforms for these devices. We propose a soft robotic model that recapitulates patient-specific hemodynamics of AS and secondary ventricular remodeling which we validated against clinical data. The model leverages 3D-printed replicas of each patient's cardiac anatomy and patient-specific soft robotic sleeves to recreate the patients' hemodynamics. An aortic sleeve allows mimicry of AS lesions due to degenerative or congenital disease, whereas a left ventricular sleeve recapitulates loss of ventricular compliance and diastolic dysfunction (DD) associated with AS. Through a combination of echocardiographic and catheterization techniques, this system is shown to recreate clinical metrics of AS with greater controllability compared with methods based on image-guided aortic root reconstruction and parameters of cardiac function that rigid systems fail to mimic physiologically. Last, we leverage this model to evaluate the hemodynamic benefit of transcatheter aortic valves in a subset of patients with diverse anatomies, etiologies, and disease states. Through the development of a high-fidelity model of AS and DD, this work demonstrates the use of soft robotics to recreate cardiovascular disease, with potential applications in device development, procedural planning, and outcome prediction in industrial and clinical settings.