The SynCardia total artificial heart (TAH) is the only FDA approved device for replacing hearts in patients with congestive heart failure. It pumps blood via pneumatically driven diaphragms and controls the flow with mechanical valves. While it has been successfully implanted in more than 1,300 patients, its size precludes implantation in smaller patients. This study’s aim was to evaluate the viability of scaled-down TAHs by quantifying thrombogenic potentials from flow patterns. Simulations of systole were first conducted with stationary valves, followed by an advanced full-cardiac-cycle model with moving valves. All the models included deforming diaphragms and platelet suspension in the blood flow. Flow stress-accumulations were computed for the platelet trajectories and thrombogenic potentials were assessed. The simulations successfully captured complex flow patterns during various phases of the cardiac-cycle. Increased stress-accumulations, but within the safety margin of acceptable thrombogenicity, were found in smaller TAHs, indicating that they are clinically viable.

The SynCardia total artificial heart (TAH) has emerged as an effective, life-saving bi-ventricular replacement system for a wide variety of patients with end-stage heart failure. While the clinical performance of the TAH is established, modern physiologic characterization, in terms of elastance behavior and pressure-volume characterization has not been defined. Herein we examine the TAH in terms of elastance using a non-ejecting left-ventricle, and then characterize the pressure-volume relationship of the TAH by varying preload and afterload parameters using a Donovan Mock Circulatory System. We demonstrate that the TAH does not operate with time-varying elastance, differing from the human heart. Further, we show that the TAH has a pressure-volume relationship behavior that also differs from that of the human heart. The TAH does exhibit Starling-like behavior, with output increasing via preload dependent mechanisms, without reliance on an alteration of inotropic state within the operating window of the TAH. Within our testing range, the TAH is insensitive to variations in afterload, however this insensitivity has a limit, the limit being the maximum driving pressure of the pneumatic driver. Understanding the physiology of the TAH affords insight into the functional parameters that govern artificial heart behavior providing perspective on differences compared to the human heart.

Antibody immobilization and function retention are important to a variety of applications, including proteomics, drug discovery, diagnostics, and biosensors. The present study investigates antibody immobilization mediated by cholesteryl succinyl silane (CSS) fibers, in comparison to hydrophobic polycaprolactone (PCL) fibers and hydrophilic plasma-treated PCL fibers. When incubated with a model protein, the formation of protein aggregates is observed on hydrophobic PCL fibers but not on the more hydrophobic CSS fibers, indicating that CSS fibers immobilize proteins through mechanisms other than hydrophobic interaction. When exposed to a limited amount of antibody, CSS fibers immobilize more antibodies than plasma-treated PCL fibers and no fewer antibodies than PCL fibers. The function retention of antibodies immobilized on the fibers is analyzed using a cell-capture assay, which shows that the antibody-functionalized CSS fibrous matrices capture 6- or 7-fold more cells than the antibody-functionalized PCL or plasma-treated PCL fibrous matrices, respectively. Data collected from the study show that the lipid fiber-mediated immobilization of antibody not only maintains the advantages of physical immobilization such as easiness and rapidness of operation but also improves function retention.

With the growth and diversity of mechanical circulatory support (MCS) systems entering clinical use, a need exists for a robust mock circulation system capable of reliably emulating and reproducing physiologic as well as pathophysiologic states for use in MCS training and inter-device comparison. We report on the development of such a platform utilizing the SynCardia Total Artificial Heart (TAH) and a modified Donovan Mock Circulation System (DMCS), capable of being driven at normal and reduced output. With this platform, clinically relevant heart failure hemodynamics could be reliably reproduced as evidenced by elevated left atrial pressure (+112%), reduced aortic flow (−12.6%), blunted Starling-like behavior and increased afterload sensitivity when compared to normal function. Similarly, pressure-volume relationships demonstrated enhanced sensitivity to afterload and decreased Starling-like behavior in the heart failure model. Lastly, the platform was configured to allow the easy addition of a left ventricular assist device (HeartMate II® at 9600 RPM), which upon insertion resulted in improvement of hemodynamics. The present configuration has the potential to serve as a viable system for training and research, aimed at fostering safe and effective MCS device use.

Abstract. In this study, electrospun polycaprolactone (PCL) fibers are plasma-treated and chemically conjugated with cholesteryl succinyl silane (CSS). In addition to Raman spectroscopy, an immobilization study of DiO as a fluorescent probe of lipid membranes provides evidence supporting the CSS coating of plasma-treated PCL fibers. Further, anti-CD20 antibodies are used as a model protein to evaluate the potential of lipid-mediated protein immobilization as a mechanism to functionalize the CSS-PCL fiber scaffolds. Upon anti-CD20 functionalization, the CSS-PCL fiber scaffolds capture Granta-22 cells 2.4 times more than the PCL control does, although the two fiber scaffolds immobilize a comparable amount of anti-CD20. Taken together, results from the present study demonstrate that the CSS coating and CSS-mediated antibody immobilization offers an appealing strategy to functionalize electrospun synthetic polymer fibers and confer cell-specific functions on the fiber scaffolds, which can be mechanically robust but often lack biological functions.

There is a need for a consistent, reproducible, and cost-effective method of determining cardiac recovery in patients who receive emerging novel therapeutics for advanced and end-stage heart failure (HF). With the increasing use of ventricular assist devices (VADs) in end-stage HF, objective device diagnostics are available for analysis. Pulsatility, one of the accessible diagnostic measures, is a variable gage of the differential between peak systolic and minimum diastolic flow during a single cardiac cycle. Following implantation of the VAD, HeartWare's HVAD records pulsatility regularly. Thus, we hypothesize that this measurement relates to the contractility of the heart and could be utilized as a metric for determining patient response to various therapeutics. In this study, therefore, we develop a translatable and effective predictive model characterizing pulsatility to determine HF status and potential HF recovery using the SynCardia Total Artificial Heart (TAH) in conjunction with a Donovan Mock Circulation System to create a simulation platform for the collection of pulsatility data. We set the simulation platform to patient conditions ranging from critical heart failure to a normal operating condition through the variation preload, afterload, and left ventricular (LV) pumping force or TAH "contractility." By manipulating these variables, pulsatility was found to accurately indicate significant (p < 0.05) improvements in LV contractility at every recorded afterload and preload, suggesting that it is a valuable parameter for the assessment of cardiac recovery in patients.

New technologies follow a predictable pattern of democratization over time. Specifically, a product that begins as merely useful over time often evolves into one that is usable, providing easy access to all functionality. If the technology survives the usability transition, it must become desirable. In this stage, the product evokes positive emotions from its users. This has been the case for the automotive industry as it moved from black colored cars driven by professional drivers and provided with its own toolbox to computers which initially required mathematicians and physicists to operate but which can now be operated by a four-year-old. This transition is now occurring before our eyes in healthcare, as medical diagnostic and treatment devices are taken out of the hands of specialized healthcare providers and placed into the hands, and homes, of patients. These useful devices now need to become usable and desirable. A successful transition will require the contributions of many disciplines, from environmental psychology, to user experience, from biomedical engineering to furniture design. It is exactly the kind of situation in which user experience thrives. This panel discusses the human capabilities, limitations, emotions and motivations which will determine whether this transition is a success. SynCardia’s Total Artificial Heart (TAH) Freedom Driver is an example of a life-sustaining medical device that is used by patients and caregivers at-home. To design the next generation Freedom Driver, SynCardia has implemented a user centered design approach. A research team performed contextual interviews and participatory design sessions with current patients, former patients, caregivers, and experienced clinicians. The research uncovered the following design considerations to be addressed in the design of the new Freedom Driver.

No abstract