In Vivo Evaluation of a Physiologic Control System for Rotary Blood Pumps Based on the Left Ventricular Pressure-Volume Loop.

Current generation continuous flow assist devices to operate at a fixed speed, which limits preload response and exercise capacity in left ventricular assist device (LVAD) patients. A feedback control system was developed to automatically adjust pump speed based on direct measurements of ventricular loading using a custom cannula tip with an integrated pressure sensor and volume-sensing conductance electrodes. The input to the control system is the integral of the left ventricular (LV) pressure versus conductance loop (PGA) over each cardiac cycle.

Miniaturized Fontan Circulation Assist Device: Chronic In Vivo Evaluation.

We have miniaturized and optimized our implantable rotary blood pump developed to provide long-term mechanical right heart support for patients who have failing Fontan circulation. The objective of this study was to evaluate the miniaturized Fontan circulation assist device (mini-FCAD) during 30-day sheep studies (n = 5). A complete right heart bypass was performed and all return flow was supported by the pump.

Chronic Ovine Studies Demonstrate Low Thromboembolic Risk in the Penn State Infant Ventricular Assist Device.

Mechanical circulatory support for children under 6 years of age remains a challenge. This article describes the preclinical status and the results of recent animal testing with the Penn State Infant Left Ventricular Assist Device (VAD). The objectives have been to 1) demonstrate acceptably low thromboembolic risk to support Food and Drug Administration approval, 2) challenge the device by using minimal to no anticoagulation in order to identify any design or manufacturing weaknesses, and 3) improve our understanding of device thrombogenicity in the ovine animal model, using multicomponent measurements of the coagulation system and renal ischemia quantification, in order to better correlate animal results with human results.

Stress and Exposure Time on von Willebrand Factor Degradation.

Despite the prevailing use of the continuous flow left ventricular assist devices (cf-LVAD), acquired von Willebrand syndrome (AvWS) associated with cf-LVAD still remains a major complication. As AvWS is known to be dependent on shear stress (τ) and exposure time (t ), this study examined the degradation of high molecular weight multimers (HMWM) of von Willebrand factor (vWF) in terms of τ and t . Two custom apparatus, i.

Chronic In Vivo Test of a Right Heart Replacement Blood Pump for Failed Fontan Circulation.

An implantable rotary blood pump was developed to provide long-term mechanical right heart support for patients who have failing Fontan circulation. The objective of this study was to evaluate the pump in vivo in a 30 day sheep study. Pump speed was set at 3,900 rpm for the duration of the study, and pump power was between 4.

Determination of Reynolds Shear Stress Level for Hemolysis.

Reynolds shear stress (RSS) has served as a metric for the effect of turbulence on hemolysis. Forstrom (1969) and Sallam and Hwang (1984) determined the RSS threshold for hemolysis to be 50,000 and 4,000 dyne/cm, respectively, using a turbulent jet. Despite the order of magnitude discrepancy, the threshold by Sallam and Hwang has been frequently cited for hemolytic potential in blood pumps.

Antibiotic-associated eosinophilic and occlusive arteritis in calves complicating preclinical studies of left ventricular assist devices.

Repeated bolus intravenous (IV) administration of large doses of beta-lactams and aminoglycosides has previously been associated with the development of eosinophilic and occlusive arterial lesions limited to the lungs in calves. Reviewing 13 years worth of records from left ventricular assist device implantation studies, morphologically identical segmental arterial lesions were present in 32 of the 56 calves receiving IV antibiotics, affecting lungs (6/50), kidneys (12/56), or lungs and kidneys (14/50). In 16 of these calves, renal arterial lesions spatially colocalized with renal cortical infarctions.

Chronic in vivo testing of the Penn State infant ventricular assist device.

The Penn State Infant Ventricular Assist Device (VAD) is a 12-14 ml stroke volume pneumatically actuated pump, with custom Björk-Shiley monostrut valves, developed under the National Heart, Lung, and Blood Institute Pediatric Circulatory Support program. In this report, we describe the seven most recent chronic animal studies of the Infant VAD in the juvenile ovine model, with a mean body weight of 23.5 ± 4.

Effective ventricular unloading by left ventricular assist device varies with stage of heart failure: cardiac simulator study.

Although the use of left ventricular assist devices (LVADs) as a bridge-to-recovery (BTR) has shown promise, clinical success has been limited due to the lack of understanding the timing of implantation, acute/chronic device setting, and explantation. This study investigated the effective ventricular unloading at different heart conditions by using a mock circulatory system (MCS) to provide a tool for pump parameter adjustments. We tested the hypothesis that effective unloading by LVAD at a given speed varies with the stage of heart failure.

Comparison of hollow-fiber membrane oxygenators with different perfusion modes during normothermic and hypothermic CPB in a simulated neonatal model.

Purpose: The objectives of this investigation were (1) to compare two hollow-fiber membrane oxygenators (Capiox Baby RX versus Lilliput 1-D901) in terms of pressure drops and surplus hemodynamic energy (SHE) during normothermic and hypothermic cardiopulmonary bypass (CPB) in a simulated neonatal model; and (2) to evaluate pulsatile and non-pulsatile perfusion modes for each oxygenator in terms of SHE levels.

Methods: In a simulated patient, CPB was initiated at a constant pump flow rate of 500 mL/min. The circuit was primed with fresh bovine blood.

Quantification of perfusion modes in terms of surplus hemodynamic energy levels in a simulated pediatric CPB model.

The objective of this investigation was to compare pulsatile versus nonpulsatile perfusion modes in terms of surplus hemodynamic energy (SHE) levels during cardiopulmonary bypass (CPB) in a simulated neonatal model. The extracorporeal circuit consisted of a Jostra HL-20 heart-lung machine (for both pulsatile and nonpulsatile modes of perfusion), a Capiox Baby RX hollow-fiber membrane oxygenator, a Capiox pediatric arterial filter, 5 feet of arterial tubing and 6 feet of venous tubing with a quarter-inch diameter. The circuit was primed with a lactated Ringers solution.

Durability testing of a completely implantable electric total artificial heart.

In vitro durability testing was conducted on the Penn State/3M electric total artificial heart (ETAH) to determine device durability and to evaluate device failures. A specialized mock circulatory loop was developed for this testing. Customized software continuously acquired data during the test period, and failures were analyzed using FMEA (failure modes and effects analysis) and FMECA (failure modes, effects, and criticality analysis) principles.

Precise quantification of pressure flow waveforms of a pulsatile ventricular assist device.

Unreliable quantification of flow pulsatility has hampered many efforts to assess the importance of pulsatile perfusion. Generation of pulsatile flow depends upon an energy gradient. It is necessary to quantify pressure flow waveforms in terms of hemodynamic energy levels to make a valid comparison between perfusion modes during chronic support.

Steady state hemodynamic and energetic characterization of the Penn State/3M Health Care Total Artificial Heart.

Total Artificial Heart (TAH) development at Penn State University and 3M Health Care has progressed from design improvements and manufacturing documentation to in vitro and in vivo testing to characterize the system's hemodynamic response and energetic performance. The TAH system is completely implantable and intended for use as an alternative to transplantation. It includes a dual pusher plate pump and rollerscrew actuator, welded electronics and battery assembly, transcutaneous energy transmission system, telemetry, and a compliance chamber.

Dynamic in vitro and in vivo performance of a permanent total artificial heart.

In vivo characterization studies were performed to compare the dynamic in vivo performance of the Penn State/3M Health Care electric total artificial heart to existing in vitro data. Fully implanted systems were utilized including the artificial heart, controller, backup batteries, compliance chamber, and transcutaneous energy transmission. Catheters were implanted to measure central venous pressure (CVP), left atrial pressure (LAP), right atrial pressure (RAP), pulmonary artery pressure (PAP), and aortic pressure (AoP).

A completely implanted left ventricular assist device. Chronic in vivo testing.

A completely implantable left ventricular assist device (LVAD) designed for permanent circulatory support has recently been tested in animals without the use of percutaneous leads, using transcutaneous energy transmission and wireless telemetry. The LVAD consists of a brushless DC motor and rollerscrew energy converter, a pusher plate actuated blood pump with a seamless segmented polyurethane blood sac, Bjork-Shiley Delrin disk monostrut valves, an implanted compliance chamber, an implanted electronic controller and battery, and a transcutaneous energy transmission system. The blood pump/energy converter assembly weighs 565 g and displaces 295 cc.

An annular compliance chamber for the Pennsylvania State University electric total artificial heart.

To eliminate the need for a separate parapleural compliance chamber, we are currently investigating the feasibility of an annular compliance chamber. This chamber wraps around the energy converter and fits between the blood pumps of the Pennsylvania State University electric total artificial heart. For the 100 cc total artificial heart, the compliance chamber volume is 76 ml and the tissue contacting surface area is approximately 85 cm2.

An electrically powered total artificial heart. Over 1 year survival in the calf.

An electric motor driven orthotopic artificial heart was implanted in a 110 kg female Holstein calf as part of a series of 12 such implants intended to demonstrate the in vivo durability and compatibility of the device. The device uses pusher plates set into motion by a reversing brushless DC motor and roller screw to alternately eject two cylindrical sac type blood pumps. The pumps use Bjork-Shiley Delrindisc convexo-concave or monostrut valves.