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At least 19 recordsLinked to original sources
PubMedDate not supplied

[Optimal mode of operation of an artificial heart].

Artificial heart operation was estimated from the view point of minimum energy consumption for the blood transport. The operation mode without breaks proved to be more economical in this respect, as compared to the mode with breaks during systole or diastole. A special control device has been designed just for the provision of uninterrupted artificial heart operation. This device improves the main functional characteristics of the artificial heart, increases the sensitivity to venous influx and provides invariance to the arterial pressure.

Heart, Artificial↗
PubMed1985

Management of a malfunctioning left ventricle in an artificial heart.

Artificial heart research is carried out in the United States, Europe, Japan, Argentina and the Soviet Union, and prolonged survival has been achieved in animals, which has increased the interest of the media and public in this field. Although recent advances are promising, device malfunction remains an obstacle to overcome in most laboratories. Relying on noninvasive monitoring techniques we were able to diagnose and correct artificial heart malfunction safely using surgical techniques employed during the heart implantation.

Animals↗
PubMed1999

Auxiliary total artificial heart: A compact electromechanical artificial heart working simultaneously with the natural heart.

Leading international institutions are designing and developing various types of ventricular assist devices (VAD) and total artificial hearts (TAH). Some of the commercially available pulsatile VADs are not readily implantable into the thoracic cavity of smaller size patients because of size limitation. The majority of the TAH dimensions requires the removal of the patients' native heart. A miniaturized artificial heart, the auxiliary total artificial heart (ATAH), is being developed in these authors' laboratories. This device is an electromechanically driven ATAH using a brushless direct current (DC) motor fixed in a center metallic piece. This pusher plate-type ATAH control is based on Frank-Starling's law. The beating frequency is regulated through the change of the left preload, assisting the native heart in obtaining adequate blood flow. With the miniaturization of this pump, the average sized patient can have the surgical implantation procedure in the right thoracic cavity without removing the native heart. The left and right stroke volumes are 35 and 32 ml, respectively. In vitro tests were conducted, and the performance curves demonstrate that the ATAH produces 5 L/min of cardiac output at 180 bpm (10 mmHg of left inlet mean pressure and 100 mm Hg of left outlet mean pressure). Taking into account that this ATAH is working along with the native heart, this output is more than satisfactory for such a device.

Blood Pressure↗
PubMed1990

Central nervous complications in subjects with artificial heart.

The artificial heart is a device for urgent solution of final heart failure. The systems used currently for this task are particularly pneumatic systems that allow only a limited life comfort for the patient. Therefore they have been used for short-term application as so-called bridge systems designed for periods preceding heart transplantation. Artificial hearts should be available for such situations. They are antithrombogenic owing to their construction and material properties and thus the patient's central nervous system is not threatened by thromboembolic complications. The Czechoslovak artificial heart TNS-Brno-VII is optimal in this respect. In experiments lasting for months, however, microembolism into the CNS from a calcified diaphragm often threatens the experimental animal. This danger can be limited both by optimal construction of the pump and by affecting the calcifying mechanism biologically, or by suitable processing of the diaphragm material that prevents calcifying nucleation. Perfect technology in the production of artificial hearts warrants complete elimination of potential air embolism into the central nervous system. Therefore the aim of further research is to design an absolutely defect-free system of the artificial heart which would eliminate any damage to the central nervous system during permanent long-lasting application, either on the basis of cerebral embolism of any origin, or on the basis of CNS hypoperfusion caused by limited pumping function of the artificial heart.

Animals↗
PubMedDate not supplied

Three-dimensional interface geometry of the human heart with the artificial heart.

The interface geometry of human and artificial hearts was defined. It included: 1) the approximate mitral orifice and mitral orifice planes; 2) the approximate tricuspid orifice and tricuspid orifice planes; 3) the long and short diameters of the aorta; 4) the long and short diameters of the pulmonary artery; and 5) the angles between the mitral orifice and tricuspid orifice planes, as well as the axes of the aorta and pulmonary artery. The orifice plane was defined as a plane such that the sum of the squared distances between the plane and points on the orifice contour was minimized. A standard coordinate system was also defined, whose origin was the centroid of the approximate mitral orifice. Its X-Y plane was the approximate mitral orifice plane. One set of interface parameters was determined using magnetic resonance images of a volunteer's heart. The angle between the approximate mitral orifice plane and tricuspid plane was found to be 19.9 degrees. The areas of the approximate mitral and tricuspid orifices were 1020 and 1655 mm2, respectively. The approximate mitral orifice was covered by a 44 x 40 mm rectangle and the approximate tricuspid orifice was covered by a 59 x 41 mm rectangle. This interface geometry is important, not only in the manufacture of artificial hearts of precise dimensions, but also in avoiding complications due to their long-term use.

Computer Graphics↗
PubMed1976

A three-month survival of a calf with an artificial heart.

An artificial heart constructed from Biomer, a polyurethane, kept a calf alive for more than three months after its natural heart was removed. During this time all of the calf's vital organs apparently functioned well. We had been able to keep similar animals alive with Jarvik III hearts made from Silastic for one month. The principal problem encountered was the infection centering along the compressed air drive lines to the artificial heart. Another problem is thrombus formation in the artificial heart. Redesigning of the artificial ventricles to improve flow patterns and reduce material discontinuities should be attempted to eliminate localized thrombus formation within the ventricles. The rapid growth of the calf has led us to examine the possibility of alternative animal models for future long-term experiments. The most encouraging aspects of this experiment were the long survival time of the calf and the very low level of blood damage caused by the artificial heart.

Alkaline Phosphatase↗
PubMed1986

Disseminated Trichosporon beigelii (cutaneum) infection in an artificial heart recipient.

A 44-year-old man with end-stage ischemic cardiomyopathy was supported with an intra-aortic balloon and The Penn State Heart (artificial) prior to orthotopic cardiac transplantation on the 14th hospital day. At the time of transplantation, intraoperative cultures of pericardial and mediastinal fluid showed growth of Trichosporon beigelii (cutaneum). Shortly thereafter the patient developed visceral dissemination of T beigelii with no associated skin lesions. He was treated with amphotericin B and rifampin, but postmortem examination showed persistent, disseminated infection.

Adult↗
PubMedDate not supplied

Control of the artificial heart.

The artificial heart (AH) is devoid of physiologic connections to the recipient's native feedback control loops. Control of an AH can be either passive or dynamic. Passive intrinsic control provides limited AH response to physiologic demands. Dynamic control requires the sensing of metabolic and hemodynamic signals and their incorporation into self-adjusting AH function. A single metabolic or hemodynamic parameter cannot provide sufficient data accurately to adjust AH pumping in response to varying blood flow demands. A combination of input control signals is required for reliable and flexible AH function. The selection of appropriate input control parameters and their incorporation into AH controller designs remains a critical step in the achievement of a permanent, totally implantable AH.

Heart Failure↗
PubMed1981

[Definitive assumption of heart function by the artificial heart].

Reproducing the function of the natural heart with an artificial heart requires a multi-disciplinary approach. Problems to be solved are anatomical, physiological, biological and technical ones. Moreover, clinical use of the artificial heart on a large scale in the near future may involve economical, ethical and legal issues. These several aspects are reviewed, and the State of the Art in 1981 is established.

Animals↗
PubMedDate not supplied

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. In vitro testing was conducted on a Penn State mock circulatory loop with glycerol/water solution at body temperature. Tests were performed to characterize the preload and afterload response, left atrial pressure control, and power consumption. A sensitive preload response was demonstrated with left atrial pressure safely maintained at less than 15 mm Hg for flow rates up to 7.5 L/min. Variations in aortic pressure and pulmonary vascular resistance were found to have minimal effects on the preload sensitivity and left atrial pressure control. In vivo testing of the completely implanted system in its final configuration was carried out in two acute studies using implanted temperature sensors mounted on the electronics, motor, and energy transmission coil in contact with adjacent tissue. The mean temperature at the device-tissue interface was less than 4 degrees C above core temperature.

Animals↗
PubMed1990

[Limiting factors in the use of the artificial heart].

The artificial heart (TAH) has become a clinical reality as a bridging device to staged transplantation. In order to manage one of the limiting factors of transplantation surgery, namely the lack of donor hearts, the use of TAH as a bridging device will be important for the next years. Nevertheless the development of TAH as a permanent prosthesis should be increasingly intensified. Biocompatibility must be the main goal of production. For the present there is no material in sight which fulfills all requirements. It might be possible though, that progresses in the development of synthetic materials will result in non-thrombotic TAH, herewith eliminating the vulnerable spot of TAH.

Biocompatible Materials↗
PubMedDate not supplied

Mean velocity and Reynolds stress measurements in the regurgitant jets of tilting disk heart valves in an artificial heart environment.

Laser Doppler velocimetry, with a high temporal resolution (1 ms time windows), was used to measure the flow field in two regions (major and minor orifices) near the aortic and mitral valves (Bjork Shiley monostrut Nos. 25 and 27, respectively) of the Penn State artificial heart. The motion of each valve was also investigated using a 1000 frame/s video camera in order to estimate the valve's closing velocity. Fluid velocities in excess of and opposite to valve closing velocity were detected near the valve, providing evidence of "squeeze flow." Maximum Reynolds shear stresses of approximately 20,000 dyn/cm2 and time-averaged Reynolds shear stresses of approximately 2000 dyn/cm2 were observed during the regurgitant flow phase. These elevated Reynolds shear stresses suggest that regurgitant jets play a role in the hemolysis and thrombosis associated with tilting disk heart valves in an artificial heart environment.

Aortic Valve↗