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The left atrial assist device (LAAD) is a novel pump that was developed specifically for the treatment of heart failure with preserved ejection fraction. The device is surgically implanted in the mitral position. This study aimed to characterize the various device-fitting configurations in the mitral annular position.Rapidly prototyped LAAD models (n = 5) were fabricated with five different driveline configurations: (A) annulus level/intra-cuff running; (B) supra-cuff/below coronary sinus (CS); (C) infra-cuff; (D) supra-annulus/supra-CS; (E) left ventricular free wall level. The 3D-printed models were implanted in extracted fresh porcine hearts (80-100 kg, adult, healthy porcine) and the proximity of anatomical structures between the driveline and CS and coronary artery (CA) were measured.All five device configurations were evaluated for fitting. For the purpose of preventing blood clot formation around the driveline, the mitral annulus (MA) as a driveline pass-way (configuration A) has been considered advantageous with the current device, in that the driveline exposure to blood has been avoided. The CS does not exist at exactly the same level as the MA, and there is less risk of injuring it than using the left atrial free wall. However, there is an inevitable risk of damaging the CA, so careful visual inspection before inserting the driveline is needed.Several options of driveline exteriorization were demonstrated, and the safety of each configuration was evaluated. Using the MA as a pathway for the driveline exit is considered to be a reasonable and safe method.

We are developing a universal, advanced ventricular assist device (AVAD) with automatic pressure regulation suitable for both left and right ventricular support. The primary goal of this computational fluid dynamics (CFD) study was to analyze the biventricular performance of the AVAD across its wide range of operating conditions. An AVAD CFD model was created and validated using in vitro hydraulic performance measurements taken over conditions spanning both left ventricular assist device (LVAD) and right ventricular assist device (RVAD) operation. Static pressure taps, placed throughout the pump, were used to validate the CFD results. The CFD model was then used to assess the change in hydraulic performance with varying rotor axial positions and identify potential design improvements. The hydraulic performance was simulated and measured at rotor speeds from 2,300 to 3,600 revolutions/min and flow rates from 2.0 to 8.0 L/min. The CFD-predicted hydraulic pressure rise agreed well with the in vitro measured data, within 6.5% at 2300 rpm and within 3.5% for the higher rotor speeds. The CFD successfully predicted wall static pressures, matching experimental values within 7%. High degree of similarity and circumferential uniformity in the pump's flow fields were observed over the pump operation as an LVAD and an RVAD. A secondary impeller axial clearance reduction resulted in a 10% decrease in peak flow residence time and lower static pressures on the secondary impeller. These lower static pressures suggest a reduction in the upwards rotor forces from the secondary impeller and a desired increase in the pressure sensitivity of the pump. The CFD analyses supported the feasibility of the proposed AVAD's use as an LVAD or an RVAD, over a wide range of operating conditions. The CFD results demonstrated the operability of the pump in providing the desired circumferential flow similarity over the intended range of flow/speed conditions and the intended functionality of the AVAD's automated pressure regulation.

Cleveland Clinic is developing a continuous-flow total artificial heart (CFTAH). This novel design operates without valves and is suspended both axially and radially through the balancing of the magnetic and hydrodynamic forces. A series of long-term animal studies with no anticoagulation demonstrated good biocompatibility, without any thromboemboli or infarctions in the organs. However, we observed varying degrees of thrombus attached to the right impeller blades following device explant. No thrombus was found attached to the left impeller blades. The goals for this study were: (1) to use computational fluid dynamics (CFD) to gain insight into the differences in the flow fields surrounding both impellers, and (2) to leverage that knowledge in identifying an improved next-generation right impeller design that could reduce the potential for thrombus formation. Transient CFD simulations of the CFTAH at a blood flow rate and impeller rotational speed mimicking in vivo conditions revealed significant blade tip-induced flow separation and clustered regions of low wall shear stress near the right impeller that were not present for the left impeller. Numerous right impeller design variations were modeled, including changes to the impeller cone angle, number of blades, blade pattern, blade shape, and inlet housing design. The preferred, next-generation right impeller design incorporated a steeper cone angle, a primary/splitter blade design similar to the left impeller, and an increased blade curvature to better align the incoming flow with the impeller blade tips. The next-generation impeller design reduced both the extent of low shear regions near the right impeller surface and flow separation from the blade leading edges, while maintaining the desired hydraulic performance of the original CFTAH design.

Cleveland Clinic’s continuous-flow total artificial heart (CFTAH) is a double-ended centrifugal blood pump that has a single rotating assembly with an embedded magnet, which is axially and radially suspended by a balance of magnetic and hydrodynamic forces. The key to the radial suspension is a radial offset between the stator-bearing bore and the magnet’s steel laminations. This offset applies a radial magnetic force, which is balanced by a hydrodynamic force as the rotating assembly moves to a “force-balanced” radial position. The journal-bearing blood passage is a narrow flow path between the left and right impellers. The intent of this study was to determine the impact of the stator-bearing bore radius on the journal-bearing hydraulic performance, while satisfying the geometric design constraints imposed by the pump and motor configuration. Electromagnetic forces on the journal-bearing were calculated using the ANSYS EMAG program, Version 18 (ANSYS, Canonsburg, PA). ANSYS CFX Version 19.2 was then used to model the journal-bearing flow paths of the most recent design of the CFTAH. A transient, moving mesh approach was used to locate the steady state, force-balanced position of the rotating assembly. The blood was modeled as a non-Newtonian fluid. The computational fluid dynamics simulations showed that, by increasing stator bore radius, rotor power, stator wall average shear stress, and blood residence time in journal-bearing decrease, while blood net flow rate through the bearing increases. The results were used to select a new bearing design that provides an improved performance compared with the baseline design. The performance of the new CFTAH-bearing design will be confirmed through upcoming in vitro and in vivo testing.

BACKGROUND The VentriFlo® True Pulse Pump (VentriFlo, Inc, Pelham, NH, USA) is a new pulsatile blood pump intended for use during short-term circulatory support. The purpose of this study was to evaluate the feasibility of the VentriFlo and compare it to a conventional centrifugal pump (ROTAFLOW, Getinge, Gothenberg, Sweden) in acute pig experiments. METHODS Pigs (40-45 kg) were supported by cardiopulmonary bypass (CPB) with the VentriFlo (n = 9) or ROTAFLOW (n = 5) for 6 h. Both VentriFlo and ROTAFLOW circuits utilized standard CPB components. We evaluated hemodynamics, blood chemistry, gas analysis, plasma hemoglobin, and microcirculation at the groin skin with computer-assisted video microscopy (Optilia, Sollentuna, Sweden). RESULTS Pigs were successfully supported by CPB for 6 h without any pump-related complications in either group. The VentriFlo delivered an average stroke volume of 29.2 ± 4.8 ml. VentriFlo delivered significantly higher pulse pressure (29.1 ± 7.2 mm Hg vs. 4.4 ± 7.0 mm Hg, p

We are developing a left atrial assist device (LAAD) that is implanted at the mitral position to treat diastolic heart failure (DHF) represented by heart failure with preserved ejection fraction.The LAAD was tested at 3 pump speeds on a pulsatile mock loop with a pneumatic pump that simulated DHF conditions by adjusting the diastolic drive. The LAAD was implanted in 6 calves, and the hemodynamics were assessed. In 3 cases, DHF conditions were induced by using a balloon inserted into the left ventricle, and in 2 cases, mitral valve replacement was also performed after the second aortic cross-clamp.DHF conditions were successfully induced in the in vitro study. With LAAD support, cardiac output, aortic pressure and left atrial pressure recovered to normal values, whereas pulsatility was maintained for both in vivo and in vitro studies. Echocardiography showed no left ventricular outflow tract obstruction, and the LAAD was successfully replaced by a mechanical prosthetic valve.These initial in vitro and in vivo results support our hypothesis that use of the LAAD increases cardiac output and aortic pressure and decreases left atrial pressure, while maintaining arterial pulsatility.

Cardiopulmonary bypass (CPB) results in short-term (3–5 h) exposure to flow with diminished pulsatility often referred to as “continuous flow”. It is unclear if short-term exposure to continuous flow influences endothelial function, particularly, changes in levels of pro-inflammatory and pro-angiogenic cytokines. In this study, we used the endothelial cell culture model (ECCM) to evaluate if short-term (≤5 h) reduction in pulsatility alters levels of pro-inflammatory/pro-angiogenic cytokine levels. Human aortic endothelial cells (HAECs) cultured within the ECCM provide a simple model to evaluate endothelial cell function in the absence of confounding factors. HAECs were maintained under normal pulsatile flow for 24 h and then subjected to continuous flow (diminished pulsatile pressure and flow) as observed during CPB for 5 h. The ECCM replicated pulsatility and flow morphologies associated with normal hemodynamic status and CPB as seen with clinically used roller pumps. Levels of angiopoietin-2 (ANG-2), vascular endothelial growth factor-A (VEGF-A), and hepatocyte growth factor were lower in the continuous flow group in comparison to the pulsatile flow group whereas the levels of endothelin-1 (ET-1), granulocyte colony stimulating factor, interleukin-8 (IL-8) and placental growth factor were higher in the continuous flow group in comparison to the pulsatile flow group. Immunolabelling of HAECs subjected to continuous flow showed a decrease in expression of ANG-2 and VEGF-A surface receptors, tyrosine protein kinase-2 and Fms-related receptor tyrosine kinase-1, respectively. Given that the 5 h exposure to continuous flow is insufficient for transcriptional regulation, it is likely that pro-inflammatory/pro-angiogenic signaling observed was due to signaling molecules stored in Weible-Palade bodies (ET-1, IL-8, ANG-2) and via HAEC binding/uptake of soluble factors in media. These results suggest that even short-term exposure to continuous flow can potentially activate pro-inflammatory/pro-angiogenic signaling in cultured HAECs and pulsatile flow may be a successful strategy in reducing the undesirable sequalae following continuous flow CPB.

We are developing a new left atrial assist device (LAAD) for patients who have heart failure with preserved ejection fraction (HFpEF). This study aimed to assess the hemodynamic effects of the LAAD under both normal heart conditions and various diastolic heart failure (DHF) conditions using a mock circulatory loop. A continuous-flow pump that simulates LAAD, was placed between the left atrial (LA) reservoir and a pneumatic ventricle that simulated a native left ventricle on a pulsatile mock loop. Normal heart (NH) and mild, moderate, and severe DHF conditions were simulated by adjusting the diastolic drive pressures of the pneumatic ventricle. With the LAAD running at 3200 rpm, data were collected at 60, 80, and 120 bpm of the pneumatic ventricle. Cardiac output (CO), mean aortic pressure (AoP), and mean LA pressure (LAP) were compared to evaluate the LAAD performance. With LAAD support, the CO and AoP rose to a sufficient level at all heart rates and DHF conditions (CO; 3.4–3.8 L/min, AoP; 90–105 mm Hg). Each difference in the CO and the AoP among various heart rates was minuscule compared with non-pump support. The LAP decreased from 21–23 to 17–19 mm Hg in all DHF conditions (difference not significant). Furthermore, hemodynamic parameters improved for all DHF conditions, independent of heart rate. The LAAD can provide adequate flow to maintain the circulation status at various heart rates in an in vitro mock circulatory loop.

In this study, a mechanical circulatory support simulation tool was used to investigate the application of a unique device with two centrifugal pumps and one motor for the biventricular assist device (BVAD) support application. Several conditions—including a range of combined left and right systolic heart failure severities, aortic and pulmonary valve regurgitation, and combinations of high and low systemic and pulmonary vascular resistances—were considered in the simulation matrix. Relative advantages and limitations of using the device in BVAD applications are discussed. The simulated BVAD pump was based on the Cleveland Clinic pediatric continuous-flow total artificial heart (P-CFTAH), which is currently under development. Different combined disease states (n = 10) were evaluated to model the interaction with the BVAD, considering combinations of normal heart, moderate failure and severe systolic failure of the left and right ventricles, regurgitation of the aortic and pulmonary valves and combinations of vascular resistance. The virtual mock loop simulation tool (MATLAB; MathWorks®, Natick, MA) simulates the hemodynamics at the pump ports using a lumped-parameter model for systemic/pulmonary circulation characteristic inputs (values for impedance, systolic and diastolic ventricular compliance, beat rate, and blood volume), and characteristics of the cardiac chambers and valves. Simulation results showed that this single-pump BVAD can provide regulated support of up to 5 L/min over a range of combined heart failure states and is suitable for smaller adult and pediatric support. However, good self-regulation of the atrial pressure difference was not maintained with the introduction of aortic valve regurgitation or high systemic vascular resistance when combined with low pulmonary vascular resistance. This initial in silico study demonstrated that use of the P-CFTAH as a BVAD supports cardiac output and arterial pressure in biventricular heart failure conditions. A similar but larger device would be required for a large adult patient who needs more than 5 L/min of support.

Background The Advanced ventricular assist device (Advanced VAD) is designed as a universal pump intended to prevent backflow in the event of pump stoppage, to maintain physiological pulse pressure, and to be used as both a left and right VAD. The purpose of this study was to evaluate the performance of the Advanced VAD as both a left and right VAD in an acute in vivo study in calves. Methods The Advanced VAD was implanted through a median sternotomy in 5 healthy calves (weight, 71.4-91.2 kg) as a left VAD (n = 3) or a right VAD (n = 2). After implantation, hemodynamic parameters, including general performance and pump stoppage, were evaluated. Results The Advanced VAD was successfully implanted as a left and right VAD without cardiopulmonary bypass. The speed range of the Advanced VAD was 2500 to 3500 rpm as a left VAD and 2000 to 2500 rpm as a right VAD. Up to 4.3 L/min was achieved for both left and right VAD configurations. To demonstrate the automatic shut-off feature, the pump was stopped without clamping the outflow graft. The outflow graft was then clamped, which produced no significant changes in the arterial pressure waveform. The pulse pressures under the left VAD configuration were 38 mm Hg, 17 mm Hg, 14 mm Hg, and 16 mm Hg at baseline, 2500 rpm, 3000 rpm, and 3500 rpm, respectively. Conclusions This acute in vivo study demonstrated the pump performance, anatomical fitting as both left VAD and right VAD, and regurgitant flow shut-off feature of the Advanced VAD.

An advanced ventricular assist device (VAD), which is under development in our institution, has specific features that allow changes in the axial rotor position and pump performance by intrapump pressure difference. However, performance could be influenced by the pump orientation because of the effect of gravity on the rotor position. The purpose of this study was to evaluate the effects of pump orientation on the pump performance, including pulse pressure and regurgitant flow through the pump when the pump was stopped. Bench testing of the VAD was performed on a static or pulsatile mock loop with a pneumatic device to simulate the native ventricle. The pump performance, including pressure-flow curve, pulsatility, and regurgitant flow, was evaluated at several angles, ranging from -90° (inlet pointed upward) to +90° (inlet pointed downward) at pump speeds of 2000, 2500, 3000, and 3500 rpm. The pump performance was slightly lower at +90° at all rotational speeds, compared with -90°. The pulse pressure on the pulsatile mock loop (80 bpm) was 50 mm Hg without pump support, remained at 50 mm Hg during pump support, and was not changed by orientation (-90°, 0°, and +90°). When the pump was stopped, the regurgitant flow was near 0 L/min at all angles. Pump orientation had a minor effect on pump performance, with no effect on pulse pressure or regurgitant flow when the pump was stopped. This indicates that the effect of gravity on the rotor assembly is insignificant.

This study aimed to evaluate a newly designed circulatory mock loop intended to model cardiac and circulatory hemodynamics for mechanical circulatory support device testing. The mock loop was built with dedicated ports suitable for attaching assist devices in various configurations. This biventricular mock loop uses two pneumatic pumps (Abiomed AB5000™, Danvers, MA, USA) driven by a dual-output driver (Thoratec Model 2600, Pleasanton, CA, USA). The drive pressures can be individually modified to simulate a healthy heart and left and/or right heart failure conditions, and variable compliance and fluid volume allow for additional customization. The loop output for a healthy heart was tested at 4.2 L/min with left and right atrial pressures of 1 and 5 mm Hg, respectively; a mean aortic pressure of 93 mm Hg; and pulmonary artery pressure of 17 mm Hg. Under conditions of left heart failure, these values were reduced to 2.1 L/min output, left atrial pressure = 28 mm Hg, right atrial pressure = 3 mm Hg, aortic pressure = 58 mm Hg, and pulmonary artery pressure = 35 mm Hg. Right heart failure resulted in the reverse balance: left atrial pressure = 0 mm Hg, right atrial pressure = 30 mm Hg, aortic pressure = 100 mm Hg, and pulmonary artery pressure = 13 mm Hg with a flow of 3.9 L/min. For biventricular heart failure, flow was decreased to 1.6 L/min, left atrial pressure = 13 mm Hg, right atrial pressure = 13 mm Hg, aortic pressure = 52 mm Hg, and pulmonary artery pressure = 18 mm Hg. This mock loop could become a reliable bench tool to simulate a range of heart failure conditions.

We observed different temporal patterns of HeartMate II left ventricular assist device (LVAD) thrombosis regarding clinical manifestations and lactate dehydrogenase (LDH) trends. We propose nomenclature for classification of LVAD thrombosis and compare patient characteristics and outcomes in each pattern of LVAD thrombosis. We reviewed electronic medical records of 362 consecutive HeartMate II devices implanted at Cleveland Clinic from October 2008 to July 2014. We categorized clinical courses of confirmed device thrombosis based on clinical manifestations and LDH patterns. Patients' characteristics, clinical variables, and outcomes were collected for comparison. From a total of 19 confirmed device thromboses, we categorized the patterns of thrombosis into three distinctive types; abrupt thrombosis (Type 1), subacute thrombosis (Type 2), and asymptomatic hemolysis (Type 3). Abrupt thrombosis (Type 1) tended to be the most morbid clinical course with acute-onset thrombosis at 56.5 (interquartile range: 44-71) days, all New York Heart Association functional class III or IV at presentation. Death and need for surgical intervention were not different in each pattern. Asymptomatic hemolysis had unique comorbidities of preexisting cardiac thrombi and preoperative bacteremia. Confirmed LVAD thrombosis has different patterns of clinical presentation and each pattern of thrombosis has unique characteristics and clinical manifestations.

Biventricular assist device (BVAD) implantation is the treatment of choice in patients with severe biventricular heart failure and cardiogenic shock. Our team has developed a miniaturized continuous flow, double-ended centrifugal pump intended for total artificial heart implant (CFTAH). The purpose of this initial in vivo study was to demonstrate that the scaled-down CFTAH (P-CFTAH) can be appropriate for BVAD support. The P-CFTAH was implanted in 4 acute lambs (average weight, 41.5 ± 2.8 kg) through a median sternotomy. The cannulation was performed through the left and right atria, and cannulae length adjustment was performed for atrial and ventricular cannulation. The BVAD system was tested at 3 pump speeds (3000, 4500, and 6000 rpm). The BVAD performed very well for both atrial and ventricular cannulation within the 3000-6000 rpm range. Stable hemodynamics were maintained after implantation of the P-CFTAH. The self-regulating performance of the system in vivo was demonstrated by the left (LAP) and right (RAP) pressure difference (LAP-RAP) falling predominantly within the range of -5 to 10 mm Hg with variation, in addition to in vitro assessment of left and right heart failure conditions. Left and right pump flows and total flow increased as the BVAD speed was increased. This initial in vivo testing of the BVAD system demonstrated satisfactory device performance and self-regulation for biventricular heart failure support over a wide range of conditions. The BVAD system keeps the atrial pressure difference within bounds and maintains acceptable cardiac output over a wide range of hemodynamic conditions.

The evaluation of pulsatile flow created by the new Cleveland Clinic continuous-flow total artificial heart (CFTAH100), which has a re-designed right impeller and motor, had not been tested in vivo. The purpose of this study was to evaluate the feasibility of pulsatility with the CFTAH100 during the application of pump speed modulation protocols in a chronic animal model.A 30-day chronic animal experiment was conducted with a calf. Five pulsatile studies were performed on the alert animal. The mean pump speed was set at 2800 rpm, and modulated sinusoidally within a range of 0 to ± 35% of mean speed, in increments of 5% at 80 beats per minute (bpm). The pressures and pump flow were collected and a pulsatility index (PI) was calculated.The calf was supported with the CFTAH100 without any major complications. The maximum and minimum pump flows changed significantly from baseline in all conditions, while the mean pump flow did not change. All flow pulsatility (FP) readings in all conditions significantly increased from baseline, and the percent modulation (%S) and FP had a strong positive correlation (r = 0.99, p 0.01). The PI also increased significantly in all conditions (maximum at %S of 35%, 2.2 ± 0.05, p 0.01), and a positive correlation between %S and PI (r = 0.99, p 0.01) was observed.The CFTAH100 showed the feasibility of creating pulsatile circulation with sinusoidal pump speed modulation.

Despite the advances in the left ventricular assist device (LVAD), there are still situations that require a biventricular assist device (BVAD) system. The purpose of this study was to explore and compare the system performance interactions with the HeartMate3 (HM3) and HeartWare (HVAD) in a BVAD configuration using the virtual mock loop (VML) simulation tool.The VML simulation tool is an in silico implementation of a lumped parameter model of the cardiovascular system with mechanical circulatory support. Patients with ejection fractions of 60%, 20%, and 15% were simulated in VML, and the HVAD and HM3 in a BVAD with ventricular cannulation were applied to simulated conditions. Pump speeds that restored baseline normal hemodynamics were determined. To determine the optimal speeds for BVAD, the left and right arterial pressures (LAP, RAP) were plotted.In the HVAD, LAP and RAP are balanced at 11 mm Hg with LVAD 3500 rpm, right ventricular assist device (RVAD) 2200 rpm; at 13 mm Hg with LVAD 3000 rpm, RVAD 1700 rpm; and at 14 mm Hg with LVAD 2500 rpm, RVAD 1300 rpm. For the HM3, at 8 mm Hg with LVAD 7000 rpm, RVAD 5000 rpm; at 9 mm Hg with LVAD 6000 rpm, RVAD 4300 rpm; and at 9.5 mm Hg with LVAD 5000 rpm, RVAD 3500 rpm.The RVAD/LVAD speed ratios required for atrial balance were approximately 0.6 for the HVAD and 0.7 for the HM3. However, the HVAD required RVAD speeds below its range of operation.

Heart failure with preserved ejection fraction (HFpEF) is characterized by diastolic dysfunction and multiple comorbidities. The number of patients is continuously increasing, with no improvement in its unfavorable prognosis, and there is a strong need for novel treatments. New devices and drugs are difficult to assess at the translational preclinical step due to the lack of high-fidelity large animal models of HFpEF. In this review, we describe the summary of historical and evolving techniques for developing large animal models. The representative methods are pressure overload models, including (1) aortic banding, (2) aortic stent, (3) renal hypertension, and (4) mineralocorticoid-induced hypertension. Diet-induced metabolic syndromes are also used. A new technique with an inflatable balloon inside the left ventricle can be used during acute/chronic in vivo surgeries to simulate HFpEF-like hemodynamics for pump-based therapies. Canines and porcine are most widely used, but other non-rodent animals (sheep, non-human primates, felines, or calves) have been used. Feline models present the most well-simulated HFpEF pathology, but small size is a concern, and the information is still very limited. The rapid and reliable establishment of large animal models for HFpEF, and novel methodology based on the past experimental attempts with large animals, are needed.

The new Advanced ventricular assist device (Advanced VAD) has many features such as improving pulsatility and preventing regurgitant flow during pump stoppage. The purpose of this study was to evaluate the effects of design modifications of the Advanced VAD on these features in vitro. Bench testing of four versions of the Advanced VAD was performed on a static or pulsatile mock loop with a pneumatic device. After pump performance was evaluated, each pump was run at 3000 rpm to evaluate pulse augmentation, then was stopped to assess regurgitant flow through the pump. There was no significant difference in pump performance between the pump models. The average pulse pressure in the pulsatile mock loop was 23.0, 34.0, 39.3, 33.8, and 37.3 mm Hg without pump, with AV010, AV020 3S, AV020 6S, and AV020 RC, respectively. The pulse augmentation factor was 48%, 71%, 47%, and 62% with AV010, AV020 3S, AV020 6S, and AV020 RC, respectively. In the pump stop test, regurgitant flow was -0.60 ± 0.70, -0.13 ± 0.57, -0.14 ± 0.09, and -0.18 ± 0.06 L/min in AV010, AV020 3S, AV020 6S, and AV020 RC, respectively. In conclusion, by modifying the design of the Advanced VAD, we successfully showed the improved pulsatility augmentation and regurgitant flow shut-off features.

With heart disease increasing worldwide, demand for new minimally invasive techniques and transcatheter technologies to treat structural heart disease is rising. Cardioscopy has long been considered desirable, as it allows direct tissue visualization and intervention to deliver therapy via a closed chest, with real-time fiber-optic imaging of intracardiac structures. Herein, the feasibility of the advanced cardioscopic platform, allowing both transapical and fully percutaneous access is reported. The latter technique, in particular, is believed to represent a milestone in the development of the cardioscope. Cardioscope prototypes were used in 7 bovine models (77.2–101.1 kg) for transapical or percutaneous insertion. Miniature custom-built, water-sealed cameras (diameters: Storz, 7 Fr; Medigus, 1.2 mm) were used. For percutaneous cardiopulmonary bypass, the pulmonary artery was occluded by a balloon catheter (Intraclude, 10.5 Fr, 100 cm) and perfused with a crystalloid solution. Cameras were inserted transapically (n = 4) through the left ventricular apex or percutaneously (n = 5) via the carotid artery. Insertion of the optimized cardioscope devices was feasible via either approach. Intracardiac structures (left ventricle, mitral valve opening/closure, chordal apparatus, aortic valve leaflets, and regurgitation) were visualized clearly and without deformation. Catheter tips were successfully bent >180° inside the left ventricle; rotation and navigation to view various intracardiac structures were feasible in all cases. This study showed the technical feasibility of direct cardioscopic visualization using transapical and percutaneous approaches. This advanced cardioscopic instrumentarium represents a promising platform for future interventions and surgery under direct visualization of the beating heart.

A novel pump, the left atrial assist device (LAAD), is a device specifically for the treatment of heart failure with preserved ejection fraction (HFpEF). The LAAD is a mixed-flow pump that is implanted in the mitral position and delivers blood from the left atrium to the left ventricle. During the development process, we aimed to explore whether device activation in torque control (TC) mode would improve the function of the LAAD. The TC mode causes adjustment of the pump speed automatically during each cardiac cycle in order to maintain a specified torque. In this study, we tested four different TC settings (TC modes 0.9, 1.0, 1.25, and 1.5) using an in vitro mock circulatory loop. Mild, moderate, and severe diastolic heart failure (DHF) conditions, as well as normal heart condition, were simulated with the four TC modes. Also, we evaluated the LAAD in vivo with three calves. The LAAD was implanted at the mitral position with four TC settings (TC modes 0.9, 1.0, 1.1, 1.2). With LAAD support, the in vitro cardiac output and aortic pressure recovered to normal heart levels at TC 1.25 and 1.5 even under severe DHF conditions with little pump regurgitation. The TC mode tested in vivo with three calves, and it also showed favorable result without elevating the left ventricular end-diastolic pressure. These initial in vitro and in vivo results suggest that the TC mode could be potentially effective, and the LAAD could be a treatment option for HFpEF patients.