Left Atrial Circulatory Assistance in Simulated Diastolic Heart Failure Model: First in Vitro and in Vivo.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Evaluation of centrifugal blood pump performances for biventricular support in the virtual simulation model.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Anti-clogging mechanisms of a motion-activated chest tube patency maintenance system: Histology and high-speed camera assessment.

The motion-activated system (MAS) employs vibration to prevent intraluminal chest tube clogging. We evaluated the intraluminal clot formation inside chest tubes using high-speed camera imaging and postexplant histology analysis of thrombus. The chest tube clogging was tested (MAS vs. control) in acute hemothorax porcine models (n = 5). The whole tubes with blood clots were fixed with formalin-acetic acid solution and cut into cross-sections, proceeded for H&E-stained paraffin-embedded tissue sections (MAS sections, n = 11; control sections, n = 11), and analyzed. As a separate effort, a high-speed camera (FASTCAM Mini AX200, 100-mm Zeiss lens) was used to visualize the whole blood clogging pattern inside the chest tube cross-sectional view. Histology revealed a thin string-like fibrin deposition, which showed spiral eddy or aggregate within the blood clots in most sections of Group MAS, but not in those of the control group. Histology findings were compatible with high-speed camera views. The high-speed camera images showed a device-specific intraluminal blood "swirling" pattern. Our findings suggest that a continuous spiral flow in blood within the chest tube (MAS vs. static control) contributes to the formation of a spiral string-like fibrin network during consumption of coagulation factors. As a result, the spiral flow may prevent formation of thick band-like fibrin deposits sticking to the inner tube surface and causing tube clogging, and thus may positively affect chest tube patency and drainage.

Analysis of Cleveland Clinic continuous-flow total artificial heart performance using the Virtual Mock Loop: Comparison with an in vivo study.

The Virtual Mock Loop (VML) is a mathematical model designed to simulate mechanism of the human cardiovascular system interacting with mechanical circulatory support devices. Here, we aimed to mimic the hemodynamic performance of Cleveland Clinic's self-regulating continuous-flow total artificial heart (CFTAH) via VML and evaluate the accuracy of the VML compared with an in vivo acute animal study. The VML reproduced 124 hemodynamic conditions from three acute in vivo experiments in calves. Systemic/pulmonary vascular resistances, pump rotational speed, pulsatility, and pulse rate were set for the VML from in vivo data. We compared outputs (pump flow, left and right pump pressure rises, and atrial pressure difference) between the two systems. The pump performance curves all fell in the designed range. There was a strong correlation between the VML and the in vivo study in the left pump flow (r2 = 0.84) and pressure rise (r2 = 0.80), and a moderate correlation in right pressure rise (r2 = 0.52) and atrial pressure difference (r2 = 0.59). Although there is room for improvement in simulating right-sided pump performance of self-regulating CFTAH, the VML acceptably simulated the hemodynamics observed in an in vivo study. These results indicate that pump flow and pressure rise can be estimated from vascular resistances and pump settings.

Effects of blood pump orientation on performance: In vitro assessment of universal advanced ventricular assist device.

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.

A simulation tool for mechanical circulatory support device interaction with diseased states.

We have created a simulation model to investigate the interactions between a variety of mechanical circulatory support (MCS) devices and the circulatory system with various simulated patient conditions and disease states. The present simulation accommodates a family of continuous-flow MCS devices under various stages of consideration or development at our institution. This article describes the mathematical core of the in silico simulation system and shows examples of simulation output imitating various disease states and of selected in vitro and clinical data from the literature.

The design modification of advanced ventricular assist device to enhance pulse augmentation and regurgitant flow shut-off.

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.

Continuous-flow total artificial heart: hemodynamic and pump-related changes associated with posture in a chronic calf model.

This study aimed to evaluate the effects of posture (sitting [lying down]/standing) on hemodynamic and pump-related parameters in calves implanted with our institution's continuous-flow total artificial heart (CFTAH). These parameters were analyzed with posture information in four calves that had achieved the intended 14-, 30-, or 90-day durations of implantation. In each animal, postoperative hourly data gathered throughout the study were used to compare average values with the animal sitting vs. standing. Pump flow became significantly higher in the standing than sitting position at the same pump speed (standing 7.9 ± 0.8, sitting 7.4 ± 1.0 L/min, p = 0.028). Systemic vascular resistance (SVR) and aortic pressure (AoP) were significantly lower in the standing than sitting position (SVR standing 779 ± 145, sitting 929 ± 206 dyne s/cm5, p = 0.027; AoP standing 93 ± 7, sitting 103 ± 7 mm Hg, p < 0.001). No substantial change occurred in pulmonary vascular resistance (PVR) or pulmonary arterial pressure (PAP) with posture (PVR standing 161 ± 39, sitting 164 ± 48 dyne s/cm5, p = 0.639; PAP standing 32 ± 3, sitting 33 ± 4 mm Hg, p = 0.340). Posture affected some hemodynamic and pump-related parameters in calves with CFTAH, with implications for patients with implanted pumps.

Use of a Mechanical Circulatory Support Simulation to Study Pump Interactions With the Variable Hemodynamic Environment.

The Virtual Mock Loop, a versatile virtual mock circulation loop, was developed using a lumped-parameter model of the mechanically assisted human circulatory system. Inputs allow specification of a variety of continuous-flow pumps (left, right, or biventricular assist devices) and a total artificial heart that can self-regulate between left and right pump outputs. Hemodynamic inputs were simplified using a disease-based input panel, allowing selection of a combination of cardiovascular disease states, including systolic and diastolic heart failure, stenosis, and/or regurgitation in each of the four valves, and high to low systemic and pulmonary vascular resistance values. The menu-driven output includes a summary of hemodynamic parameters and graphical output of selected flows, pressures, and volumes in the heart's four chambers as well as in the pulmonary artery and aorta. New tools to augment experimental research on implantable heart-assist devices and to increase our understanding of patient-specific pump interactions are in high demand. The purpose of this ongoing study is to demonstrate the use of a system analysis computer simulation to explore and better comprehend the interactions of mechanical circulatory support pumps with a more extensive combination of patient-specific or simulation conditions than can be established by practical experimentation. Usability is an important factor in constructing computer models for research purposes, and among our primary objectives in creating this simulation model were to make it as portable and useful as possible outside the lab environment, by people not involved in the creation of its operational software.

Anatomical study of the Cleveland Clinic continuous-flow total artificial heart in adult and pediatric configurations.

The purpose of this study was to assess the smallest possible body sizes of patients in whom the Cleveland Clinic continuous-flow total artificial heart for adult (CFTAH) and pediatric configurations (P-CFTAH) can fit. One of the most critical dimensions is the vertebra-to-sternum distance at the junction of the right atrium to the inferior vena cava (V-S distance). Our previous CFTAH anatomical fitting study suggested that the CFTAH would fit patients of V-S distance ≥ 7.5 cm and the P-CFTAH of V-S distance ≥ 5.25 cm (70% of 7.5 cm). To confirm this, we assessed the relationship between body surface area (BSA) and V-S distance in 15 adult patients (BSA 1.86-2.62 m2) and 31 pediatric patients (BSA 0.17-1.80 m2) whose computed tomography scans were available. We found a highly significant correlation between BSA and V-S distance (p < 1.0 × 10-25). It appears that the CFTAH will fit in most patients with BSA ≥ 1.0 m2 (corresponding height of ≥ 130 cm and age of 9 years) and the P-CFTAH in patients with BSA ≥ 0.3 m2 (corresponding height of ≥ 55 cm and age of 1 month). Further anatomical fitting studies are needed to evaluate the two pump models inside human chests to determine the smallest patient size/critical dimensions and device port configurations.

Deairing Techniques for Double-Ended Centrifugal Total Artificial Heart Implantation.

The unique device architecture of the Cleveland Clinic continuous-flow total artificial heart (CFTAH) requires dedicated and specific air-removal techniques during device implantation in vivo. These procedures comprise special surgical techniques and intraoperative manipulations, as well as engineering design changes and optimizations to the device itself. The current study evaluated the optimal air-removal techniques during the Cleveland Clinic double-ended centrifugal CFTAH in vivo implants (n = 17). Techniques and pump design iterations consisted of developing a priming method for the device and the use of built-in deairing ports in the early cases (n = 5). In the remaining cases (n = 12), deairing ports were not used. Dedicated air-removal ports were not considered an essential design requirement, and such ports may represent an additional risk for pump thrombosis. Careful passive deairing was found to be an effective measure with a centrifugal pump of this design. In this report, the techniques and design changes that were made during this CFTAH development program to enable effective residual air removal and prevention of air embolism during in vivo device implantation are explained.

Thrombotic Depositions on Right Impeller of Double-Ended Centrifugal Total Artificial Heart In Vivo.

The development of total artificial heart devices is a complex undertaking that includes chronic biocompatibility assessment of the device. It is considered particularly important to assess whether device design and features can be compatible long term in a biological environment. As part of the development program for the Cleveland Clinic continuous-flow total artificial heart (CFTAH), we evaluated the device for signs of thrombosis and biological material deposition in four animals that had achieved the intended 14-, 30-, or 90-day durations in each respective experiment. Explanted CFTAHs were analyzed for possible clot buildup at "susceptible" areas inside the pump, particularly the right pump impeller. Depositions of various consistency and shapes were observed. We here report our findings, along with macroscopic and microscopic analysis post explant, and provide computational fluid dynamics data with its potential implications for thrombus formation.

Generating pulsatility by pump speed modulation with continuous-flow total artificial heart in awake calves.

The purpose of this study was to evaluate the effects of sinusoidal pump speed modulation of the Cleveland Clinic continuous-flow total artificial heart (CFTAH) on hemodynamics and pump flow in an awake chronic calf model. The sinusoidal pump speed modulations, performed on the day of elective sacrifice, were set at ±15 and ± 25% of mean pump speed at 80 bpm in four awake calves with a CFTAH. The systemic and pulmonary arterial pulse pressures increased to 12.0 and 12.3 mmHg (±15% modulation) and to 15.9 and 15.7 mmHg (±25% modulation), respectively. The pulsatility index and surplus hemodynamic energy significantly increased, respectively, to 1.05 and 1346 ergs/cm at ±15% speed modulation and to 1.51 and 3381 ergs/cm at ±25% speed modulation. This study showed that it is feasible to generate pressure pulsatility with pump speed modulation; the platform is suitable for evaluating the physiologic impact of pulsatility and allows determination of the best speed modulations in terms of magnitude, frequency, and profiles.

Median Sternotomy or Right Thoracotomy Techniques for Total Artificial Heart Implantation in Calves.

The choice of optimal operative access technique for mechanical circulatory support device implantation ensures successful postoperative outcomes. In this study, we retrospectively evaluated the median sternotomy and lateral thoracotomy incisions for placement of the Cleveland Clinic continuous-flow total artificial heart (CFTAH) in a bovine model. The CFTAH was implanted in 17 calves (Jersey calves; weight range, 77.0-93.9 kg) through a median sternotomy (n = 9) or right thoracotomy (n = 8) for elective chronic implantation periods of 14, 30, or 90 days. Similar preoperative preparation, surgical techniques, and postoperative care were employed. Implantation of the CFTAH was successfully performed in all cases. Both methods provided excellent surgical field visualization. After device connection, however, the median sternotomy approach provided better visualization of the anastomoses and surgical lines for hemostasis confirmation and repair due to easier device displacement, which is severely limited following right thoracotomy. All four animals sacrificed after completion of the planned durations (up to 90 days) were operated through full median sternotomy. Our data demonstrate that both approaches provide excellent initial field visualization. Full median sternotomy provides larger viewing angles at the anastomotic suture line after device connection to inflow and outflow ports.

Progress on the design and development of the continuous-flow total artificial heart.

Cleveland Clinic's continuous-flow total artificial heart has one motor and one rotating assembly supported by a hydrodynamic bearing. The right hydraulic output is self regulated by passive axial movement of the rotating assembly to balance itself with the left output. The purpose of this article is to present progress in four areas of development: the automatic speed control system, self-regulation to balance right/left inlet pressures and flows, hemolysis testing using calf blood, and coupled electromagnetics (EMAG) and computational fluid dynamics (CFD) analysis. The relationships between functions of motor power and speed, systemic flow, and systemic vascular resistance (SVR) were used for the sensorless speed control algorithm and demonstrated close correlations. Based on those empirical relationships, systemic flow and SVR were calculated in the system module and showed good correlation with measured pump flow and SVR. The automatic system adjusted the pump's speed to obtain the target flow in response to the calculated SVR. Atrial pressure difference (left minus right atrial pressure) was maintained within ±10 mm Hg for a wide range of SVR/pulmonary vascular resistance ratios, demonstrating a wide margin of self-regulation under fixed-speed mode and 25% sinusoidally modulated speed mode. Hemolysis test results indicated acceptable values (normalized index of hemolysis <0.01 mg/dL). The coupled EMAG/CFD model was validated for use in further device development.

Computational Fluid Dynamics Model of Continuous-Flow Total Artificial Heart: Right Pump Impeller Design Changes to Improve Biocompatibility.

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.

Total Artificial Heart Computational Fluid Dynamics: Modeling of Stator Bore Design Effects on Journal-Bearing Performance.

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.

Characterization and Development of Universal Ventricular Assist Device: Computational Fluid Dynamics Analysis of Advanced Design.

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.

Left atrial assist device to treat patients with heart failure with preserved ejection fraction: Initial in vitro study.

OBJECTIVES: Many patients with heart failure have preserved ejection fraction but also diastolic dysfunction, with no effective therapy. We are developing a new pump (left atrial assist device, LAAD) for implantation at the mitral position to pump blood from the left atrium to sufficiently fill the left ventricle. The purpose of the initial in vitro study was to demonstrate that the LAAD can reduce left atrial pressure (LAP) and increase cardiac output (CO) while maintaining arterial pulsatility and normal aortic valve function using a proof-of-concept device. METHODS: The LAAD concept was tested at 3 pump speeds on a pulsatile mock loop with a pneumatic pump that simulated the normal function of the native ventricle as well as 3 levels of diastolic heart failure (DHF 1, 2, and 3) by adjusting the diastolic drive pressure to limit diastolic filling of the ventricle. RESULTS: Without the LAAD, CO and aortic pressure (AoP) decreased dramatically from 3.8 L/min and 100 mm Hg at normal heart condition to 1.2 L/min and 35 mm Hg at DHF 3, respectively. With LAAD support, both CO and AoP recovered to normal heart values at 3200 rpm and surpassed normal heart values at 3800 rpm. Furthermore, with LAAD support, LAP recovered to almost that of the normal heart condition at 3800 rpm. CONCLUSIONS: These initial in vitro results support our hypothesis that use of the LAAD increases CO and AoP and decreases LAP under DHF conditions while maintaining arterial pulsatility and full function of the aortic valve.

The Effects of Preserving Mitral Valve Function on a Left Atrial Assist Device: An In Vitro Mock Circulation Loop Study.

We are developing a left atrial assist device (LAAD) to pump blood from the left atrium to the left ventricle for patients who have heart failure with preserved ejection fraction (HFpEF). This study aimed to assess the hemodynamics with the LAAD implanted at two different levels: the mitral valve (MV) level, after removing the MV; and the supravalvular level, preserving MV function conditions using an in vitro mock circulatory loop. Normal heart and mild, moderate, and severe diastolic heart failure conditions were simulated, and the LAAD was set at three different speeds. Without the LAAD support, cardiac output (CO) decreased from 3.7 to 1.1 L/min, aortic pressure (AoP) decreased from 100 to 33 mm Hg, and left atrial pressure (LAP) increased from 16 to 23 mm Hg as the diastolic function became impaired. With high pump support after removing the MV, CO and AoP readings were comparable with those for preserved MV function (CO reached 3.9-4.1 L/min, AoP reached more than 110 mm Hg, and LAP dropped to 16-17 mm Hg under both conditions at high pump speeds). In the mock circulatory loop, our LAAD appeared to have sufficient ability to maintain the hemodynamic status at both positions.