Evaluation of polyurethane sac type blood pump after 232 and 288 days total artificial heart (TAH) pumping without anticoagulant.
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Animals↗
Biomedical subjects
A Kouno
Publications and source records attributed to A Kouno.
Three goats survived for 288 days, 243 days and 232 days with hybrid total artificial heart (HTAH).
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Animals↗
In vitro and in vivo evaluation of a jellyfish valve for practical use.
A practical model (Model-1) of a jellyfish valve was developed, which was composed of a valve seat and a flexible membrane. The valve seat has 12 spokes to hold the membrane, and is made of solution-cast polyurethane coated with segmented polyurethane or Cardiothane. The flexible membrane is 200 microns thick, and made of segmented polyurethane or Cardiothane by a casting method. The valves were built into a sac type blood pump. In mock circulation tests, this jellyfish valve revealed performance superior to Bjork-Shiley (B-S) valves. No stagnation point was observed in the flow visualization study, and durability testing is ongoing beyond 7.5 months. The valves were used in animal artificial heart experiments for up to 112 days with good performance. No thrombi were formed on the valve membrane or around the spokes. Although a ring thrombus was observed behind the valve, it would be prevented by perfect adhesion of the valve seat to the blood pump. The plasma free hemoglobin level was less than 2 mg/dl during these experiments. These results suggest that a jellyfish valve (Model-1) is useful in ventricular assist devices, and in short-term bridge use of a total artificial heart.
Animals↗
Use of a total right heart bypass model for analyses of abnormal hemodynamics in total artificial heart animals, and the function and regulatory mechanisms of a natural heart.
By fixing the function of one ventricle, a total right heart bypass model can clarify the function and regulatory mechanism of the natural heart, and the etiology of abnormal hemodynamics in TAH animals such as increased CVP blood pressure and hepatic congestion. The pulmonary artery of a right heart bypass in a goat was clamped proximally; the pulmonary circulation was thus supplied entirely by the artificial heart and the systemic circulation by the natural heart. This model enabled studies of long-term effects of an artificial right heart on systemic circulation at a right heart output of 80-100 ml/kg/min; the response of the natural left heart to changes in output of the right heart; and the response of the natural left heart and artificial right heart to treadmill exercise. It was found that only slight increase in CVP or no increase in blood pressure was observed during the experiment (112 days); a rapid increase in output of the RAH resulted in an increase in left atrial pressure, stroke volume and output of the left ventricle, and a decrease in its heart rate at rest; and significant increase in both artificial right heart and natural left heart output and heart rates were observed during treadmill exercise, despite the marked decrease in left atrial pressure. The above results suggest that the increase in CVP and blood pressure in total artificial heart animals are not due to factors involving the artificial right heart, and that although left ventricular function acts in accordance with Starling's law at rest, this is no longer true during treadmill exercise.
Animals↗
Fabrication of a jellyfish valve for use in an artificial heart.
For a valve to be fabricated seamlessly into an artificial heart (AH) blood pump, a jellyfish valve has been developed, in which a thin membrane is fixed at the center of a valve seat having several spokes to protect against prolapse of the membrane. The valve is superior in performances to a Björk-Shiley valve, and reveals good blood compatibility. The valve would be very useful not only for AH animal study, but for future clinical use in infants to adults. Several institutions are already trying the valve. In this paper, the fabrication of the jellyfish valve is introduced, and in vitro and in vivo results summarized. A computer aided design (CAD) system was developed to cut a male wax mold of the valve seat. The input parameters to the CAD are diameter, height, thickness of rim, number of spokes, width and thickness of spokes, etc. Jellyfish valves with diameters of 4 to 27 mm have already been fabricated for many types of AHs and assist pumps.
Animals↗
The second and third model of the flow transformed pulsatile total artificial heart.
For the purpose of future total implantation, a new pulsatile total artificial heart, a flow transformed pulsatile total artificial heart (FTPTAH), in which the continuous flow from a single centrifugal pump (CFP) was converted to pulsatile flow by switching two three-way valves that could alternately perfuse the systemic and pulmonary circulation, was proposed, and the data from the prototype model were reported. As the next step, the second model, in which a CFP and a spool valve (SV) driven with a solenoid were fabricated in one piece, was made and tested in a mock circulatory system. The system could send 4.7 L/min of pulsatile output alternately to the pulmonary artery and aorta, with 30 and 100 mmHg afterload, respectively, at 3000 rpm CFP. However, three problems were encountered: the output was not enough, mixture or inversion of venous and arterial blood in the CFP would occur, and heat generation at the solenoid was very severe. To solve these problems, a third model was designed in the current study. To increase pump output, hydrodynamic analysis was performed. The SV was divided into inlet and outlet to control the blood mixture or inversion. To suppress heat generation, each SV was driven back and forth by two solenoids, one on each side of the SV. The model revealed satisfactory results in a mock circulatory system.
Biomedical Engineering↗
A new apparatus for chronic observation of the microcirculation in situ to evaluate artificial organ performance.
Chronic study of the peripheral circulation and metabolism is very important in evaluation of artificial organ performance. However, there has been no way to observe the microcirculation in situ, chronically and continuously, without restriction. In this study, the authors developed a new apparatus that could be implanted and connected to an artificial organ that would allow continuous observation of the microcirculation while the subject is awake. The apparatus uses a charge coupled device (CCD) under a new principle: thin living tissue, such as mesentery, is put directly on a highly integrated CCD and transilluminated with a light emitting diode (LED). The vascular nets in the tissue are projected onto the CCD like a contact photograph, which is sent to a television screen and can be analyzed for motion and function. A 0.5 inch CCD with 25K pixels was used in this study. The cover glass of the CCD was removed so the tissue would be able to directly contact the CCD surface. The CCD, as well as LED, were molded with hard polyurethane as electrical insulation. The apparatus is 35 mm in diameter and 10 mm high with a micro stand for lighting with the LED, which is easy to implant in a goat or calf. The resolution of this apparatus was tested by putting a micro scale on the CCD surface. Several tenths of micrometers could be seen. In an animal experiment with a rabbit, configurations of arterioles and venules and their motions could be observed continuously for a night until the electrical insulation was broken. This method might be a strong weapon in artificial organs research.
Animals↗
Results of animal experiments using an undulation pump total artificial heart: analysis of 10 day and 19 day survival.
An undulation pump is a special rotary blood pump in which rotation of a brushless DC motor is transformed to an undulating motion by a disc in the pump housing attached by means of a special link mechanism. In the blood pump, a closed line between the disc and housing moves from the inlet to the outlet by this undulating disc motion, which sucks and pushes the blood from the inlet to the outlet. Because the same phenomena occurs at both sides of the disc, a continuous flow is obtained when the motor rotational speed is constant. The pump flow pattern can be easily changed from continuous flow to pulsatile flow by controlling the motor drive current pattern. A seal membrane made of segmented polyurethane protects the blood from invading the link mechanism as well as the motor. UPTAH is fabricated with two undulation pumps and two brushless DC motors. Its size is 75 mm in diameter and 80 mm long, and it has one of the great advantage of no compliance chamber required in the system. UPTAHs were implanted under cardiopulmonary bypass (CPB) into the chest cavities of 16 goats, each weighing between 41 and 72 kg. No anticoagulant and antiplatelet agent was used after the surgery. The left atrial pressure was automatically controlled to prevent its elevation and sucking of the atrial wall into the atrial cuff. The following results were obtained: (1) UPTAHs fit well into all the goats; (2) the longest survival was 19.8 days, the cause of death was bleeding from the aortic anastomosis; (3) No thrombus was observed in the blood pump despite no anticoagulant use. Hemolysis depended upon the length of CPB during surgery. When CPB time was within 2 hours, hemolysis level returned to baseline within a few days of the surgery. UPTAH is a promising implantable TAH, because of its small size and easy controllability.
Animals↗
Blood compatibility of the jellyfish valve without anticoagulant.
The blood compatibility of the jellyfish valve was studied. Artificial heart (AH) blood pumps incorporating jellyfish valves were connected to 18 goats as total artificial hearts (TAHs) and pumped for 1 to 125 days without anticoagulant or antiplatelet drugs. No thrombus was formed on the valve membrane or around the valve seat. Scanning electron microscopy showed almost no platelet deposition or microfibrin clot formation on the valve membrane, including its central region; the spokes of the valve seat were also free from platelet and microfibrin clots. No calcification was observed during these tests, and plasma free hemoglobin was between 2 and 7 mg/dl. The jellyfish valve revealed good blood compatibility, even without anticoagulant use.
Animals↗
A new pulsatile total artificial heart using a single centrifugal pump.
A new pulsatile total artificial heart (TAH) system, combining a single centrifugal pump (CFP) with two three-way valves, was developed. One port of each three-way valve was connected to the inlet and outlet of a CFP, respectively. The other two ports of each valve ware connected to the right and left atrium, pulmonary artery, and aorta. The CFP can perfuse the pulmonary and systemic circulation alternately with pulsatile flow. A prototype system composed of a Sarns' CFP and solenoid valves was connected to a mock circulatory system resulting in 1) a pulsatile TAH that could be produced with a single CFP, 2) 5 L/min of pulsatile output with a normal flow wave form that can be obtained alternately on the right and left side by switching the solenoid valves, and 3) flow balance between the left and the right that could be controlled easily by the length of switching duration. This new system could be miniaturized and is feasible for a totally implantable TAH.
Blood Flow Velocity↗
Long-term preservation of a beating heart in an artificial environment.
The natural heart could be preserved in the beating state, with appropriate afterload, for more than 24 hrs if supported by blood compatible artificial organs and biomedical engineering techniques. An artificial environment was developed using this philosophy. The system was constructed from four subsystems: circulatory, respiratory, metabolic, and environmental. In the circulatory subsystem, diastolic pressure was held at 70 to 100 mmHg by computer aided peripheral resistance, and a left ventricular assist device (LVAD) could be added when cardiac function was weakened. The respiratory subsystem was composed of an artificial lung and computer aided gas mixer for O2, CO2, and air, which kept blood PO2 and PCO2 within physiologic levels. In the metabolic subsystem, glucose and insulin were injected by infusion pump so as to maintain blood sugar within 100 to 200 mg/dl, whereas the environmental system preserved the isolated heart at 37 degrees C in a sterile water bath. Goats' hearts were connected to this system, and continued to beat for a maximum of 24 hours.
Animals↗
A newly designed jellyfish valve for an artificial heart blood pump.
Bjork-Shiley and Hall valves used in most artificial heart blood pumps have often induced problems, which include 1) An expensive valve must be used even when the AH is used for only a few days, 2) Ring thrombus was often formed at the interface between the valve ring and blood pump, seamless fabrication was not possible, and 3) Mechanical failure often occurred. To improve these circumstances, a new jellyfish valve was designed and manufactured. The valve has a simple structure: The center of a thin circular polyurethane membrane is fixed on a polyurethane base plate, which has many holes or slits to reduce flow resistance and help hold the membrane during the diastolic phase. In a mock circulation study, the valve displayed performance similar to the Bjork-Shiley valve. A small amount of regurgitant flow was observed at valve closure, in comparison with the Bjork-Shiley valve. It was recognized in the flow visualization study that the central region of the membrane was washed out well by the flapping of the membrane. This jellyfish valve is promising for use in a AH blood pump.
Equipment Design↗
Can total artificial heart animals control their TAH by themselves? One year survival of a TAH goat using a new automatic control method (1/R control).
A total artificial heart (TAH) goat survived for 360 days on the new automatic control method (1/R control), in which the cardiac output of the TAH can be controlled through the cardiovascular center by making it function by reflecting the beta-adrenergic reaction in peripheral vascular resistance. This is thought to be the only long-term, real-time, measurable parameter by which information on the activity of the cardiovascular center can be received directly by the TAH system. In this goat, the hemodynamic parameters (RAP, AoP, and so forth) were kept within physiologic limits when control was stable, and the cardiac output was automatically increased in response to exercise, not unlike that in the natural heart. There were no abnormal blood chemical or hormone data except at end stage. Based on these results 1/R can be considered a physiologic control method for a TAH.
Animals↗