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Purpose The aim of this study was to assess a new pump's performance and function by using a virtual mock loop (VML) system for device characterization and mapping. Methods We are developing a novel miniaturized left ventricle assist device (LVAD) configured for transapical insertion (Perfusions Solutions Inc., South Euclid, OH). The results of pump testing in the laboratory, such as pressure-flow performance curves, were used for the analysis of its function as an LVAD. The VML system was programmed to mimic various types of heart failure and provide hemodynamic pressure values before and after activation of LVAD. The circulatory conditions of the VML system were systolic heart failure (SHF), diastolic HF (DHF), and both systolic and diastolic HF (BHF). Results Before and after pump activation with SHF condition and with a pump speed of 14000 RPM, aortic pressure (AoP) increased from 71/50 to 99/97 mm Hg, pulmonary artery pressure (PAP) changed from 44/36 to 44/33 mm Hg, mean left atrium pressure (mLAP) decreased from 25 to 18 mm Hg, mean right atrium pressure (mRAP) increased from 7 to 10 mm Hg; with DHF, AoP changed from 116/81 to 129/113 mm Hg, PAP was 45/34 to 45/31 mm Hg, mLAP was 18 to 15 mm Hg, mRAP was 10 to 12 mm Hg; with BHF, AoP was 65/46 to 98/96 mm Hg, PAP was 44/36 to 45/33 mm Hg, mLAP was 26 to 19 mm Hg, mRAP was 7 to 10 mm Hg. (Figure A; pressure-volume curve with BHF, B; pressure curve with BHF without LVAD, 14000 RPM and 16000 RPM of the pump speed) Conclusion Due to the test results from the VML system, the new LVAD for transapical insertion could have the ability enough to ease symptoms of the patients with various types of heart failure based on results from VML system. [ABSTRACT FROM AUTHOR]

End-stage heart failure is frequently encountered in complex congenital heart disease. Currently, we are developing a pediatric continuous flow total artificial heart (P-CFTAH). Due to the variations in congenital heart anomalies, the device should be suitable for multiple inflow and outflow structures. The purpose of this study is to evaluate the fitness of a replica of the prototype of P-CFTAH in different ages, weights and morphologies. The P-CFTAH pump was derived from the adult CFTAH configuration by downsizing it with a scale factor of 0.70 (1/3 of total volume, Fig. 1a). The 3D-printed models of the pump were evaluated for anatomical fit during open-heart surgery for a variety of congenital heart anatomies. A total of 23 patients were enrolled so far (3.2-30 kg) and divided into 2 groups after the fitting study: fit or non-fit group. The pre-op thoracic size (mm), heart size (mm), cardio thoracic ratio (CTR) were measured using their pre-op chest X-rays and the differences between the 2 groups were statistically analyzed. Among the 23 patients, 13 patients were assigned to the fit group, and 10 patients assigned to the non-fit group after the intraoperative visual assessment. There were significant differences (p < 0.0001) between fit/non-fit groups for body weight (BW), height (Ht), body surface area (BSA), thoracic and heart size (A, B, C, D in Fig. 1b). The cutoff values of each are, BW: 5.71 kg, Ht: 66.5 cm, BSA: 0.31 m2, A: 148.0 mm, B: 84.0 mm, C: 57.0 mm, D: 76.0 mm, and the area under curve of all of the parameters were >0.94. The CTR (B/A in Fig.1b) showed no significant differences among groups. This study revealed suitability of the P-CFTAH for wide range of pediatric patients, and the range of proper fit was evident. Further studies including the evaluation of the pump performance in vivo and the development of even smaller pumps for the patients below the cutoff line. [ABSTRACT FROM AUTHOR]

Prevention of air introduction during mechanical circulatory support device implant is critical for a successful outcome. A substantial amount of air may be introduced into the circulation during pump to outflow port connection, which may become detrimental for optimal pump function and long-term survival. In this study, we evaluated techniques of seamless, airless connection of double-ended centrifugal pump (continuous-flow total artificial heart [CFTAH]) in vivo. The airless CFTAH connection techniques were evaluated in acute in vivo (n=2) CFTAH implants (Jersey calves, weight: 77.8 and 80.8 kg). Techniques consisted of pump priming with normal saline (Fig. 1 A) and application of specifically designed connection sleeve (Fig 1B). The silicone sleeve (0.3-0.5 mm thick) was prototyped using multilayer dip-coating technique over a 3D-printed mandrel. A suture line was added along the long axis, to enable easy removal. Deairing sleeve was pre-placed on each outflow port (conduit) and proximal port (port) ends (Fig.1 C). The present air was evacuated upward from an open line. The conduit and pump ports were connected within the sleeve (Fig.1 D), with air being fully excluded from circuit. The CFTAH was started at the minimum speed (2,200 rpm) after connection. The CFTAH pump were successfully primed with saline prior to implant to remove entrapped air. The completely seamless pump connection and exclusion of air from pump and outflow grafts has been found feasible. There were no clinical signs of air embolism in the pulmonary or systemic circulation observed during the experiment. The seamless connection of CFTAH to outflow grafts using specifically designed connection sleeve and its easy removal was demonstrated to be feasible. Device development is ongoing and will aim to address optimal geometry, size and material selection. [ABSTRACT FROM AUTHOR]

In patients with severe biventricular heart failure (HF) and cardiogenic shock, use of biventricular assist device (BVAD) can be a treatment of choice. We are developing an advanced ventricular assist device (AVAD) intended to serve as universal pump for left and/or right heart failure (Fig.1 A,B). The purpose of this initial in silico simulation study was to demonstrate that AVAD design can be suitable for biventricular support. The virtual mock loop (VML) was developed (MATLAB; MathWorks®) to simulate hemodynamic parameters as they surge through the BVAD-supported systolic HF cardiovascular system. The AVAD used as in BVAD configuration was in 2 speeds (3400 rpm left, 2000 rpm right) to get comparable systemic flow and pressure outputs. LVAD support was adjusted to maintain 5.0 L/min total systemic flow. For BVAD, the added RVAD support was adjusted to maintain left and right atrial pressure (LAP-RAP) at 3-5 mm Hg. The BVAD performance was maintained very well for both left ventricular (L-AVAD) and right ventricular (R-AVAD) support within specified speed range (Fig1 C,D). L- AVAD speed of 3000 - 3500 rpm provided sufficient support for the case of severe left and right systolic heart failure, assuming there was no aortic valve regurgitation. At the simulated condition, with L-AVAD support, the aortic valve remains closed and the systemic pressure has reduced pulse. A stable hemodynamics were maintained. The atrial pressure difference (LAP-RAP) resulted to be sensitive to the right pump speed, though was balanced whenever there was any positive flow through the pulmonary valve. Introduction of R-AVAD support to the L-AVAD support caused the left atrial pressure to increase resulting in increased filling of the left ventricle and a corresponding increase in aortic pulsatility. These initial in silico study demonstrated that use of the universal AVAD as BVAD supports cardiac output and arterial pressure in biventricular HF condition. [ABSTRACT FROM AUTHOR]

The virtual mock loop (VML) is a computer program that simulates the hemodynamic interactions of one or more mechanical circulatory support (MCS) pumps and its circulatory environment. It has been used to study MCS devices being developed at the Cleveland Clinic. The scope of the VML has been expanded, over time, to include several different device and circulatory models. Recently, the advanced VML has been designed to address management and storage of various mathematical models and case-scenarios, and pre-recorded data from in vivo , and in vitro studies. The VML contains several different lumped parameter models can be selected and evaluated. The VML has been updated to store and organize data from different origins in way that makes comparison easier (Fig.1). The recent updates to the VML help the user study either: the effects of changing a mathematical model, validating existing models with recorded experimental data, or the composition of new models by combining existing device and circulatory models in different combinations and configurations. The system enables the user to adjust the parameters of a clinical case with a faster but more simple model, before switching to a more comprehensive one for fine tuning and rendering on the system interface. User-friendly comparison of data generated by the VML and from other sources makes it an effective tool for studying the mathematical models, the broad range of mechanical circulatory devices and circulatory hemodynamics and offers reproducibility of blood pump testing at low-cost. Fig.1 The VML showing a list of available models (A), and comparing in vivo and in silico data (B). [ABSTRACT FROM AUTHOR]

The latest version of the continuous flow total artificial heart (CFTAH), which incorporates a novel stacked motor to improve passive self-regulation of pressure difference between the left and right atria, and reduce pump rotor over-excursion, was tested in vivo in a calf model to assess operational performance. The CFTAH was implanted in a calf and run at various pump operating conditions including mean pump speeds from 2400 to 3600 RPM, sinusoidal speed modulations from 0 to 25%, and speed modulation rates from 80 to 120 B.M. It was also tested under various combinations of simulated high and low systemic vascular resistance and pulmonary vascular resistance via outlet graft clamping and administration of a Nitroprusside respectively. The CFTAH responded to all control inputs and ran as expected during the experiment. The head curves of the right and left pumps generated from measured pressures, measured right flow and calculated left flow, were consistent with in vitro data on this pump. The passive atrial pressure regulation performed well in the normal operating range, and there were no signs of excessive rotor axial displacement during extreme pressure excursions as had been seen in the previous versions of the pump. The left atrial pressure was unusually low throughout most of the experiment and we believe that this may have been due to partial blockage of the of the left inflow cuff proximal to the pressure line tap. This led to several left inlet suction conditions and extreme pressure conditions. The replacement of the standard, single stack stator motor with the new dual stator stack motor resulted in better passive regulation of the pressure difference between the left and right atria. Also, the extreme pressure conditions resulting from left inlet suction events did not cause the pump's rotor to rub against the volute housing as had been seen in previous versions of the pump. Even though the self-regulation was acceptable, shifting of the regulation characteristic to increase the nominal LAP-RAP value will improve the regulation further, and this modification will be implemented prior to the next in vivo experiment. [ABSTRACT FROM AUTHOR]

Purpose Biventricular assist device (BVAD) implantation is the treatment of choice in patients with severe biventricular heart failure (BHF) and cardiogenic shock. We previously developed a miniaturized continuous flow double-ended centrifugal pump intended for total artificial heart implant (CFTAH). The purpose of this initial in vitro study was to prove that scaled down CFTAH can be suitable for biventricular support. Methods The CFTAH was tested in BVAD configuration at 2 pump speeds (4500 and 6000 rpm) on a pulsatile mock loop with two pneumatic ventricles that simulated normal and heart failure conditions (moderate and severe) by adjusting the systolic and diastolic drive pressures to simulate hemodynamics of the failing biventricular function. Results The BVAD performance was maintained very well for both atrial and ventricular cannulation within the 4500 - 6000 rpm range. A stable hemodynamics were maintained, and the pump's self-regulating performance was confirmed with the most of atrial pressure difference (LAP-RAP) falling within ±5-15 mm Hg in (Mod.) and severe (Sev.) right (RHF) and left HF (LHF) conditions. Left and right pump flows (LPF and RPF) and total flow (TF) increased as the BVAD speed was increased (Figure). The TF was higher than LPF and RPF due to output from the native ventricles, and the LPF was higher than RPF with pump speed of 6,000 rpm, but the TF appeared balanced due to larger native right ventricular output vs. native left ventricle with given condition. Conclusion These initial in vitro study demonstrated that use of the CFTAH as BVAD supports cardiac output and arterial pressure in BHF conditions. In vivo evaluation of this technology is currently pending. [ABSTRACT FROM AUTHOR]

Purpose Heart transplantation in infants and children is an accepted therapy for congenital heart disease, but donor organ availability remains unstable. Mechanical circulatory support is another standard option, but there is a lack of implantable devices due to size and functional range. The purpose of this study was to evaluate in vivo performance of the initial prototype of an infant continuous-flow total artificial heart (I-CFTAH) with one motor and one rotating assembly supported by a hydrodynamic bearing. Methods The I-CFTAH was designed to cover a range of 3 kg infant to 9 kg child (flange diameter - 26.9 mm; length - 44 mm), with nominal design point was matched to a 6 kg child, requiring 1.0 L/min of flow. I-CFTAH was tested using in silico virtual simulation mock loop (VML; MATLAB; MathWorks®) and simulated the hemodynamics as they surge through the system implanted with blood pump (run at 0.5 L/min for 3 kg infant). Lumped-parameter model including systemic/pulmonary circulation, values for impedance, beat rate, and blood volume was used. Results The in silico experiments showed intended performance of scaled down pump (left and right pump flows - 0.5 L/min at 4380 RPM). The difference between the left and right atrial pressures was maintained within ± 5-15 mm Hg. Simulation of I-CFTAH was successfully performed and allowed creating arterial pulsation with this device. Conclusion The present simulation-based approach showed feasibility of I-CFTAH design. The I-CFTAH met the proposed requirements for self-regulation, performance and pulse modulation. Further in vitro validation and in vivo implantation will be necessary to explore this technology in more detail. [ABSTRACT FROM AUTHOR]