Are the Jarvik artificial ventricles limited by inflow resistance?

The pneumatic total artificial heart has been assumed to be inflow limited. Mock circulation studies on the Jarvik-5 and Jarvik-7 artificial ventricles seemed to support this assumption because a Starling's response comparable to the natural heart was not achieved. Unfortunately, mock circulation studies do not separate the effects of valvular regurgitation from inflow resistance. By using a simple filling tank, filling times were determined for the Jarvik ventricles that were a function of inflow resistance alone. Theoretical maximum cardiac outputs based on these inflow resistance-dependent filling times were then calculated. For filling pressures around 5 mmHg and under modest diastolic vacuum of 5 cm H2O, the Jarvik ventricles yield a theoretical cardiac output as good as the natural heart's. Thus, inflow resistance is not a limiting factor and valvular regurgitation is left as the most likely cause of a less than optimal Starling's response on mock circulation and in vivo.

[Automatic control of an artificial heart with an autonomous energy source]

Specific features and particularities in the design of the artificial heart control systems are considered, operated by various engines with a radioisotope energy source. The operation results showed the need in a complex approach to the problem solution. It should be based on optimized constructions, methods and principles of functioning for all ingradients of the artificial heart from the viewpoint of automatic control.

A new right ventricular cardiac assist device

At present no good method of assisting the right ventricle of the heart exists. This paper presents a new and effective approach to assisting the right ventricle of the heart which can be utilized independently or during cardiac surgery. Through implementation of this method, and timed inflation and deflation of several types of balloon catheters in the pulmonary artery, distal pulmonary arterial flow is augmented with subsequent unloading of the right side of the heart. This approach will be of great benefit in the treatment of atherosclerotic and congenital heart disease as well as in many cases of pulmonary hypertension.

Successful use of a left ventricular assist device in cardiogenic shock from massive postoperative myocardial infarction

A 41-year-old man underwent an uneventful aorta-coronary bypass for unstable angina pectoris. Four hours later, a massive anterior wall myocardial infarction resulted in cardiac arrest. Conventional resuscitative means were not effective. A left ventricular assist device (LVAD) was successfully employed for 94 hours. The patient is alive and well 8 months postoperatively.

[Blood heat exchangers for the artificial heart using a radioisotope power source]

A design of a vascular heat exchanger enabling it to establish in experiments with animals the degree of the possible specific-capacity thermal loads has been devised. The performance results may be taken account of in designing implantable appliances of assistive circulation and artificial heart.

[The research programme "Artificial Heart" at the 2nd Department of Surgery, University of Vienna: a ten year review (author's transl)]

The experimental and clinical results are presented of the research programme "Artificial Heart" carried out by the 2nd Department of Surgery, University of Vienna. In particular, an assessment of the clinical experience in 177 patients with the intra-aortic balloon pump is documented and it is concluded that only limited cardiac support is possible by this pump. In view of this fact more efficient methods of mechanical circulatory support, such as the interaortic auxilliary ventricle, the aortic "Windkessel" ventricle with guiding balloon, and two types of ventriculo-aortic bypass ventricle were tested with regard to their haemodynamic and long-time efficacy. The transatrio-aortic auxilliary ventricle (E-LVAD) was also clinically tested in 11 patients. In conclusion the problems of total mechanical heart replacement are discussed.

Evolution of the solenoid-actuated left ventricular assist system: integration with a pusher-plate pump for intra-abdominal implantation in the calf

The performance of an implantable left ventricular assist system (LVAS) utilizing a pulsed solenoid energy converter and a pusher-plate blood pump has been characterized in vitro and in vivo. A microprocessor-based electronic control system makes the LVAS completely self-regulating over the range of operating conditions and provides considerable flexibility in various assist modalities. Over forty thousand hours of in vitro and in vivo operating experience has been accumulated with current systems, and significant progress has been acheived in system durability and reliability. A new toggle latch has provided nearly a year of failure-free operation on the bench, without measurable wear. Energy converter efficiencies of 50% have been demonstrated. In vivo evaluation has been highlighted by an animal experiment still in progress after nearly four months of fault-free, continuous synchronous pumping.

[Artificial heart control system]

To develop a system for the artificial heart control the algorhythm of the latter, with the blood pressure in the aorta acting as a regulation parameter, was analyzed on its mathematical model. The results of the algorhythm operation in three model situation describing transitional processes under physical efforts, stress and resuscitation are reported. The technical implemetation of the described algorhythm is set forth and a comparison of the obtained experimental data versus the design curves is made.

The artificial heart. Progress and promise

A multidisciplinary group has designed, fabricated, and evaluated an artificial heart. The heart consists of two smooth-surfaced sac-type pumps, two pneumatic power units, and an electronic control system. The artificial heart has been employed in 22 calves. A variety of problems have been encountered and overcome and a significant improvement in pump design has been made. As a result, a gradual increase in survival times has occurred. The last two calves in which the heart was tested lived for 60 and 42 days respectively. These animals ate well and gained weight. The ability of the control system to balance the output of the two pumps over long periods of time and to automatically increase cardiac output with treadmill exercise has been confirmed. No insurmountable problems in the development of the artificial heart have been identified. The date that an artificial heart will be available for clinical use depends on the availability of funds and on the tenacity of the investigators.

An intracorporeal (abdominal) left ventricular assist device. Initial clinical trials

We have initiated clinical trials with an intracorporeal (abdominal) partial artificial heart and ten preterminal postcardiotomy patients have been studied. During profound left ventricular failure, the device captures the entire cardiac output from the apex of the left ventricle at low pressures (20 to 40 mm Hg) and ejects (at 80 to 150 mm Hg) into the infrarenal abdominal aorta; the biological aortic valve opens only intermittently and the entire systemic circulation is pump generated. The device is six to ten times more effective than intra-aortic balloon pumping in man and has maintained systemic perfusion during clinical asystole and ventricular fibrillation. We have documented that the profoundly depressed postcardiotomy left ventricle, initially incapable of ejection, can recover during total left ventricular unloading with the abdominal left ventricular assist device support over a seven-day period.

Exponential growth and future of artificial organs

One hundred thousand (100,000) people are living--thanks to Artificial Kidneys. We need more emphasis on Home Dialysis. The immediate future will bring us: WAK (Wearable Artificial Kidney) FAK (Filtrating Artificial Kidney) PAK (Peritoneal Artificial Kidney) HAK (Hemoperfusion Artificial Kidney). Intra-aortic balloon pumps and transapical left ventricular bypass may offer patients now dying from heart failure, a possibility to either recover or be maintained until an artificial heart is available. Our aim is to create an Artificial Heart to totally replace the irreparably sick human heart. We have obtained survival times up to more than six months after total replacement of the natural heart in calves. Dr. Steve Jacobsen's Artificial Arm is activated by electromyographic signals that are derived from the shoulder muscles. The Artificial Eye makes use of direct stimulation of the visual cortex of the brain by arrays of electrodes situated against the visual cortex. For the Artificial Ear, we stimulate the fibers of the eighth nerve by threading platinum wires up into the cochlea. Deaf volunteers can hear rhythm, loudness and some pitch.

[General problems in long-surviving experimental animals following complete heart replacement]

Total heart replacement was performed in 7 calves. All animals were alive at 3 weeks, and four survived more than 2 months up to 121 days. Failure of the pumping equipment was responsible for death in each case. At autopsy increase both in size of the right atrium and of liver weight and evidence of thromboembolism were regular findings.

Surface characteristics of the cardiac prostheses in vivo

The pseudoneointima (PNI) deposited onto a cardiac prosthesis surface reflects many factors of biocompatibility, surface morphology, flow distribution, design, animal's physiological condition, and duration. In the evaluation of any prosthesis, the PNI is one of the prime considerations from both material and functional standpoints. Historically, Dacron fabric has been used as an internal lining for cardiac prostheses. However, we have observed cracks on the Dacron fibers, fiber fracture, fiber protrusion, and poor attachment to the diaphragm, which can cause potentially disastrous complications. In addition, there are basic differences in the PNI formation on aldehyde-treated pericardium and natural aortic valves as compared to the Dacron fabric. 1) Minimal degeneration takes place on the chemically treated natural tissue compared with the fabtic surface. Intact cells on the tissue suggest a greater compatibility. In later specimens (13 and 24 days), there is active cell infiltration onto the pericardium structure with capillary formation. 2) The deposits on natural tissue are mostly fibrin, with minimum cellular involvement and a trend toward reduction in thickness. 3) Fibroblast cells are found on the natural tissue as early as 7 days but were not observed on the Dacron fabrics. Based on these findings, the Dacron fabric-covered diaphragm studied was not favorable for use in long-term implantation of cardiac prostheses.

[Components of an implanted artificial heart and the medico-technical requirements]

The task of designing and providing power supply for an implanted artificial heart (AH) is a many-sided complex problem that includes a number of medico-biological, technical, physical, power-supply and other factors. The analysis of the AH components and the mentioned basic medico-technical requirements permits it to outline the ways and means for a rational solution of this complicated problem. The greatest attention is paid to the analysis of and future prospects for the use of different power sources and methods of power conversion.

Use of artificial heart for basic cardiovascular research

Improved technology in artificial heart development and implantation studies in unanesthetized calves have stimulated a new model for cardiovascular research. Independent control of the left and right ventricles, replacement of the natural right atrium with an artificial atrium (with a compliant inner diaphragm) are illustrated as examples of new methods to study the cardiovascular system. Preliminary results in three calves suggest that synchronous ventricular pumping is not required for total circulatory maintenance. In four calves a passive artificial right atrium was shown to decrease outflow obstruction to the right ventricle. A compliant inner deiapragm demonstrated a reduction in the amplitude of the atrial C and V waves. The effects of volume and drug infusion on peripheral vascular response in the presence of controlled artificial heart pumping (which does not respond to direct neural or hormonal influences) further illustrate the efficacy of this preparation as a new model for cardiovascular research.

Survival for 18 days with a Jarvik-type artificial heart

This is a report of an experiment wherein a calf had its natural heart replaced with an artificial heart and survived for 18 days and 20 hours. All measured physiologic parameters remained normal until the fourteenth day. Thereafter a gradual persistent rise in venous pressure and signs of a decreased cardiac output occurred. However, the animal outwardly appeared normal until the eighteenth day. During the nineteenth day it became comatose and was killed. At autopsy large thrombi were found in both atria, impairing ventricular filling, resulting in venous congestion and diminished cardiac output. This extended survival time and our ability to understand and eliminate the problems associated with artificial heart implantation give support to our hope that artificial hearts for man will be possible in the not too distant future.

Comparative evaluation of artificial ventricles in the United States

A cooperative, comparative evaluation of nine artificial ventricles was performed on two standardized mock circulations. The ventricles included five air-driven diaphragm types, three sack types and a mechanically driven type. The slopes of the ventricular output curves varied from 0.04 to 0.88 at 0 to 5 Torr filling pressure and the maximum ventricular output varied from 3.8 to 11.9 liters/min at 100 Torr outflow pressure. All ventricles had decreased output with increased outflow pressures (70 to 130 Torr). Hemolysis index ratio (HI test/HI std) for HI std equals 0.024 plus or minus .005 (plus or minus 1 SD) g/100 liters (N equals 12), was +21.5 and +6.9 for a Dacron cloth and fibril heart, respectively, +2.0 to +2.86 for three sack ventricles, and +3.2 for a smooth diaphragm ventricle. The mechanical ventricle with a sinusoidal driving waveform and smooth surface had the lowest hemolysis, HI equals 0.008 plus or minus 0.003 (plus or minus 1 SD) (N equals 6). Sack ventricles caused marked hemolysis if the walls touched during systole. Ventricular dimensions varied: weight 116 to 700 g, length 9.2 to 18.7 cm, and volume 235 to 430 ml. Performance data was returned to each individual laboratory which resulted in modification of ventricular design in at least three instances. Comparative, standardized testing of artificial ventricles may shorten development time and provide performance criteria for application in man.

Nuclear power for the artificial heart

Studies showed that a totally implantable nuclear-powered artificial heart is practicable, and consequently a prototype system development program was initiated in July 1973. Basic testing of the prototype should be completed in 1977, with extensive studies to qualify the device for clinical use running at least into the early 1980s.

Long-term effects of the artificial heart

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