The total artificial heart

Control and Treatment of Hemostasis in Cardiovascular Surgery

The hemostasis protocol applied at the Cardiovascular Surgery Dept. of La Pitié Hospital has greatly reduced thromboembolic accidents and excessive bleeding, with consequent benefits for patients as well as cost reduction. Protocol also has been adopted for patients implanted with a circulatory assist device or a TAH. This paper presents our criteria on supervision and treatment of coagulation with such patients, who reflect all the acquired pathology in clinical hemostasis. From 04/86 to 07/94, 82 patients underwent TAH as a bridge to transplantation. Mean age: 38. Overall duration of mechanical support: 1930 days (mean: 23), of which 137 and 603 for 2 patients. Average duration of CPB: 150 min. Systematic approach to complex TAH-blood interaction and pre-operative multiple organ dysfunction used to control bleeding and/or thromboembolism after CPB. In addition to routine tests, specific regular testing was carried out at least once a day for platelet functions, for thrombin formation and its regulatory pathways, and for the fibrinolytic system. Patients were treated with small doses of Heparin, large doses of Dypyridamole, small doses of Aspirin, modulated doses of Aprotinin, Ticlopidine, Pentoxifylline, FFP, as well as Fibrinogen and AT III concentrates. Dosage was adapted to patient's clinical profile as well as to test interpretation criteria to provide personalized treatment. DIC, widely present in its different phases, was thus diagnosed and treated. All DIC bleeding was controlled, making it possible to detect other causes of post-operatory bleeding and use blood derivates rationally. There were no thromboembolic complications and no iatrogenic bleeding. TAH explantation shows no evidence of macroscopic clots in high risk sites, confirmed by microscopic analysis.

Polymeric trileaflet prosthetic heart valves: evolution and path to clinical reality

Present prosthetic heart valves, while hemodynamically effective, remain limited by progressive structural deterioration of tissue valves or the burden of chronic anticoagulation for mechanical valves. An idealized valve prosthesis would eliminate these limitations. Polymeric heart valves (PHVs), fabricated from advanced polymeric materials, offer the potential of durability and hemocompatibility. Unfortunately, the clinical realization of PHVs to date has been hampered by findings of in vivo calcification, degradation and thrombosis. Here, the authors review the evolution of PHVs, evaluate the state of the art of this technology and propose a pathway towards clinical reality. In particular, the authors discuss the development of a novel aortic PHV that may be deployed via transcatheter implantation, as well as its optimization via device thrombogenicity emulation.

Demonstration of the Bacterial-Biomaterial Interface in Implant Specimens

Bacterial infection can be a problem associated with biomaterial implants especially with the total artificial heart or other cardiovascular prostheses such as ventricular assist devices, intravenous catheters, ventriculo-atrial shunts, pacemaker electrodes and, rarely, prosthetic heart valves. Bacterial commensals such as Staphylococcus epidermidis, which is ordinarily non-infective in human skin and mucous membranes, is now recognized as an opportunistic pathogen of biomaterial implants, particularly cardiovascular prostheses. In these implantations the S. epidermidis undergoes transformation to produce mucoid or polysaccharide extracellular coating substances. The latter promote bacterial adherence to biomaterial surfaces and protect the bacteria to some extent against antibiotics and host defense mechanisms. The result is increased virulence of the slime-producing strains. A number of techniques have been developed in our laboratories which facilitate identification of such bacterial pathogens on biopsy or postmortem specimens. These light and analytical electron microscopic methodologies include special cytochemical staining and rapid drying and embedding methods. Their efficacy and accuracy have been verified by studies on cultured and subcultured pathogens which are more time consuming. It is of interest that the microscopic methods showed the presence of macrophages as well as neutrophils on the specimens.

Total artificial heart--concepts and clinical use

End-stage congestive heart failure remains the leading cause of death in the United States. Despite advances in medical treatment, it also remains the most common reason for admission to the hospital. The gold standard of treatment for the failing heart, orthotopic heart transplantation, is limited by a shortage of donor hearts. There are also a significant number of patients who are not transplant candidates due to comorbid conditions and/or inability to tolerate immunosuppressive therapy. To meet the need for this latter group, the medical field has embraced ventricular assist device (VAD) therapy to extend survival and improve quality-of-life for the end-stage cardiac patient. This therapy, however, has been currently limited to the failing left ventricle and is still fraught with complications that limit long-term and widespread use. The total artificial heart, as currently available with two devices, is rapidly becoming the treatment of choice for biventricular failure.

Current status of the total artificial heart

Although heart transplantation remains the gold standard for patients who remain in advanced heart failure despite optimal medical therapy, limited donor supplies allows for just >2000 transplant each year in the United States. Recent enthusiasm has developed for the role of mechanical circulatory support for this ever-growing population of sick patients. Although much attention has been directed toward ventricular assist devices, less information is available regarding the role of the total artificial heart. Indeed, efforts in this latter technology have allowed the relatively recent deployment of a variety of complete circulatory assist devices. The purpose of this article is to review the historical development, current use, and future role of total artificial hearts.

Costs and insurance coverage associated with permanent mechanical cardiac assist/replacement devices in the United States

Each year over 50,000 persons in the United States could potentially benefit from some form of permanent cardiac replacement or assistance. Approximately 7000 of these persons get on the waiting list for a transplant, and 2300 are transplanted. About 2000 patients are reportedly exposed to a mechanical cardiac assist device, most often as a bridge to transplant. The majority of persons who might benefit from cardiac replacement are never referred for treatment and, thus, the number of deaths on the waiting list is a misleading indicator of access to transplantation and overall patient mortality. The total economic burden associated with coronary artery disease and congestive heart failure now exceeds $140 billion each year, with approximately $700 million directly spent on heart transplant procedures alone. If a viable total artificial heart is devised to replace a failed heart, or a ventricular assist system to permanently assist a failing heart, direct aggregate expenditures alone are likely to be somewhere between $5.4 and $24.0 billion annually. Based on individual patient care costs, as well as aggregate national expenditures, insurers will be reluctant to pay for the permanent use of such devices, even though cost is reportedly not a consideration in coverage decisions. Today, medical benefits and added value are concepts that will shape the coverage determination process, as will increasingly liberal policies regarding payment for treatment costs in relationship to clinical trials. Nonetheless, resource allocation and rationing decisions loom large as strange "characters at play" on an international economic "stage," while being "directed" by worldwide health care needs.

Shaft/shaft-seal interface characteristics of a multiple disk centrifugal blood pump

A multiple disk centrifugal pump (MDCP) is under investigation as a potential left ventricular assist device. As is the case with most shaft driven pumps, leakage problems around the shaft/shaft seal interface are of major interest. If leakage were to occur during or after implantation, potential events such as blood loss, clotting, blood damage, and/or infections might result in adverse effects for the patient. Because these effects could be quite disastrous, potential shaft and shaft seal materials have been investigated to determine the most appropriate course to limit these effects. Teflon and nylon shaft seals were analyzed as potential candidates along with a stainless steel shaft and a Melonite coated shaft. The materials and shafts were evaluated under various time durations (15, 30, 45, and 60 min), motor speeds (800, 1,000, 1,200, and 1,400 rpm), and outer diameters (1/2 and 3/4 inches). The motor speed and geometrical configurations were typical for the MDCP under normal physiologic conditions. An air and water study was conducted to analyze the inner diameter wear, the inner temperature values, and the outer temperature values. Statistical comparisons were computed for the shaft seal materials, the shafts, and the outer diameters along with the inner and outer temperatures. The conclusions made from the results indicate that both the tested shaft seal materials and shaft materials are not ideal candidates to be used for the MDCP. Teflon experienced a significant amount of wear in air and water studies. Nylon did experience little wear, but heat generation was an evident problem. A water study on nylon was not conducted because of its molecular structure.

Electrohydraulic-clamshell heart with energy converter inside the compliance reservoir

Two new ideas on the electrohydraulic actuation of blood pumps have been combined. The first idea was to put the energy converters that propel the hydraulic fluid inside the compliance reservoir instead of having them separate. Compactness of the device and better cooling of the energy converter by the surrounding fluid are two major advantages of this approach. Secondly, we put the pumping membrane inside a clamshell that fits over a soft ventricle (1). The ventricle can be implanted first, after which the shell is slid over it. These two ideas have resulted in devices described in this paper. Preliminary in vitro and in vivo data are presented.

A moving-actuator type electromechanical total artificial heart--Part II: Circular type and animal experiment

A new type of electromechanical total artificial heart (TAH) based on circular rolling-cylinder mechanism was developed to overcome critical problems in motor-driven artificial hearts such as large size and difficulties in fitting the heart to atrial remnants and arterial vessels. Its performance and reliability were evaluated in mock circulation and in an animal implant experiment. The total weight and volume of the pump is 650 g and 600 mL, respectively. This new pump was implanted in a calf for total heart replacement and 96 h of survival was achieved. The whole system, including pump, controller, and control algorithm performed well enough to improve the prospect of eventual clinical application of our TAH system.

A moving-actuator type electromechanical total artificial heart--Part I: Linear type and mock circulation experiments

A new type of motor-driven total artificial heart system with a moving-actuator mechanism has been developed. The prototype system consists of a brushless dc motor inside of a rolling-cylinder, two arc-shaped pusher-plates and two polyurethane sacs. The moving-actuator type electromechanical pump has structural advantages of small size and light weight, as compared to other reported motor-driven pumps with fixed-actuator mechanisms. The results of the mock circulation tests are reported in this paper with a cardiac output of 9 L/min at an aortic pressure of 120 mmHg and a heart rate of 120 bpm. The fulfillment of the basic control requirements of the artificial heart was also confirmed, i.e., preload sensitive and afterload insensitive cardiac output response and balanced right and left ventricular outputs.

A multiple disk centrifugal pump as a blood flow device

A multiple disk, shear force, valveless centrifugal pump was studied to determine its suitability as a blood flow device. A pulsatile version of the Tesla viscous flow turbine was designed by modifying the original steady flow pump concept to produce physiological pressures and flows with the aid of controlling circuitry. Pressures and flows from this pump were compared to a Harvard Apparatus pulsatile piston pump. Both pumps were connected to an artificial circulatory system. Frequency and systolic duration were varied over a range of physiological conditions for both pumps. The results indicated that the Tesla pump, operating in a pulsatile mode, is capable of producing physiologic pressures and flows similar to the Harvard pump and other pulsatile blood pumps.

Effects of pneumatic artificial heart driver on the rate of isovolumic pressure rise

The aim of the research was to investigate the effects of three parameters of the artificial heart's performance on the (+) dP/dt max. Specifically, the effects of heart rate, left-sided drive pressure, and percent systole (the independent variables) on the (+) dP/dt max (the dependent variable) were examined. The study was conducted using a mock circulation which was connected to an artificial heart. Data were collected using the COMDU software developed for the computer which monitors the artificial heart. Stepwise regression analysis was used to test the three hypotheses. Hypothesis one stated the heart rate would significantly effect the (+) dP/dt max. The hypothesis was not supported. Hypothesis two stated the percent systole would significantly effect the (+) dP/dt max. Hypothesis two was also not supported. Hypothesis three stated the drive pressure would significantly effect the (+) dP/dt max. The hypothesis was supported as drive pressure accounted for 4% of the variance in (+) dP/dt max; however, the results were not clinically significant. Limitations in the study were multicollinearity among the independent variables, small sample size, and the inability of the mock circulation to represent human responses.

Multigated radionuclide study of the total artificial heart

A permanent total artificial heart, the Jarvik-7, was implanted into a 61-year-old male with a severe cardiomyopathy. Gated radionuclide studies were performed in the patient both prior to surgery and following implantation. Preoperative gated radionuclide cardiac studies revealed marked left ventricular enlargement, severe hypokinesis and a left ventricular ejection fraction of 10%. The right ventricle was moderately enlarged with a 27% ejection fraction. Following implantation of the Jarvik-7 artificial heart, gated cardiac studies were performed with a computer gated by a signal from the heart controller. The left ventricular ejection fraction was 69% and the right ventricular ejection fraction was 62%. This compared to a theoretical ejection fraction of 74% for each ventricle based on chamber anatomy. There was excellent ventricular emptying. Phase analysis showed uniform diaphragm motion. The use of gated cardiac studies in humans may prove helpful in evaluating mechanical problems with the artificial heart, such as malfunction of the diaphragm, before they become clinically apparent.

Restoring cardiac function: an emerging spectrum of therapeutic options

A spectrum of techniques for restoring cardiac function is emerging. Among patients with global congestive heart failure (CHF), cardiac transplantation may help a small minority for whom allografts are available; the total artificial heart may eventually benefit a larger number. For patients with left-sided CHF, parallel-assist techniques maximally augment cardiac output. In-series techniques can help others without major arrhythmias and some residual cardiac output. As compared with parallel assist, in-series methods offer lesser hemodynamic augmentation but greater intrinsic reliability and the possibility of deactivation of support for hours or days without increased risk. Additional advantages include simplicity of management and documented long-term clinical efficacy.

Comparison of an implanted abdominal aortic counterpulsation device with the intraaortic balloon pump in a heart failure model

The abdominal aortic counterpulsation device is a round pumping chamber with a valveless opening which is implanted retroperitoneally on the abdominal aorta. The Utah driver is connected to the device through an air conduit and is synchronized on the electrocardiographic signal to provide diastolic aortic augmentation. For comparison an intraaortic balloon was also driven by the Utah driver system. The abdominal aortic counterpulsation device (stroke volume = 30, 40 and 60 ml) and the intraaortic balloon pump (balloon volume = 20 ml) were tested in dogs with acute left ventricular failure. The abdominal aortic counterpulsation device was also tested in normal animals. In acute left ventricular failure the abdominal aortic counterpulsation device at a stroke volume of 30, 40 or 60 ml decreased left ventricular end-diastolic pressure by an average of 28.56 (p less than 0.001), 39.56 (p less than 0.001) and 44.14% (p less than 0.005), respectively; aortic end-diastolic pressure by 24.11 (p less than 0.001), 26.67 (p less than 0.001) and 19.57% (p less than 0.01); and aortic systolic pressure by 18.56 (p less than 0.002), 26.0 (p less than 0.001) and 22.43% (p less than 0.005). It increased cardiac index by 27.58 (p less than 0.02), 35.59 (p less than 0.005) and 43.42% (p less than 0.001) and it provided peak aortic diastolic augmentation of 64.5 (p less than 0.001), 69.78 (p less than 0.001) and 74.43% (p less than 0.001), respectively, above the control aortic end-diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative in vitro study of the closing characteristics of Björk-Shiley and Bicer-Val tilting disc mitral valve prostheses

The replacement of mitral valves has become a relatively common procedure in cardiac surgery. Information concerning losses due to backflow through the valve may be used to assess and compare the physical characteristics of commercially available prostheses. A simple apparatus based on an artificial ventricle was used to measure closing volume, leakage volume, total volume, leakage rate and closing time on a beat by beat basis for Björk-Shiley and Bicer Val prosthetic mitral valves. The Björk-Shiley valve opened to 60 degrees and displayed a smaller closing volume than the Bicer Val, which opened to 75 degrees; and the Björk-Shiley displayed higher leakage than the Bicer Val, thus reducing its advantage in terms of closing volume. Overall, the Bicer-Val showed about 1 ml greater reflux per beat than the Björk-Shiley. Study of a Bicer-Val, modified to have an opening angle of 80 degrees, confirmed that valve closing volume was a function of opening angle.

Ethical issues related to the artificial heart

This paper is a general survey of ethical issues related to the artificial heart. It begins by looking at the history of funding of the artificial heart program through the National Institute of Health in 1965. Attention is paid to the problem of the lack of planning related to social, ethical, economic, and legal implications. The paper then deals with three areas of ethical concerns. They are those issues relating to the experimental versus therapeutic benefits, the cost, and public involvement with a private interest.

Obstacles to developing and using technology. The case of the artificial heart

For some observers, the artificial heart represents the latest, and perhaps the most flagrant example of the health system's tendency to favor the rapid introduction of expensive but ineffective technologies over efforts to prevent disease and to improve access to care (5;6;19;44;45). Even if it can be perfected, they argue, its opportunity cost in terms of other foregone health benefits would be exorbitant. The ultimate failing of the health care system, it would seem, is its failure to establish mechanisms to select among alternative uses of resources. If such mechanisms had existed, some critics believe that the quest for an artificial heart never would have begun and certainly its premature clinical uses could have been prevented (6;45).

The artificial heart. Costs, risks, and benefits--an update

As discussed above, approximately 32,500 persons aged 55 to 70 years with end-stage heart disease may be potential candidates for the artificial heart each year. However, continued application of a protocol that requires informed consent by the patient effectively limits the pool to 12,000 annually. Estimates of the cost of the artificial heart include charges for the surgical procedure, device and console, and continuing medical surveillance. These estimates range from a low of $100,000 to a high of $300,000 per patient in the initial year. Assuming a five-year, 51% survival and an initial cost of $100,000, total program costs in the fifth year are projected to be $1.3 billion for a pool of 12,000 patients, and $3.8 billion for 32,500 patients. These projected costs are associated with anticipated increases in life expectancy. For those individuals destined to develop heart disease, the anticipated average increase is approximately half a year. In comparison, heart transplant patients who meet the surgical criteria but who do not receive a new heart do not survival beyond six months. In an era of limited resources, it is imperative that such a potentially expensive innovation as the artificial heart be compared carefully with other social and medical programs designed to extend life and improve its quality. Such a comparison will require a full understanding of the likely costs and benefits of the device. A viable artificial heart would greatly alter current treatment for end-stage cardiac disease. More patients would benefit from this therapy than currently benefit from heart transplants, and the costs of caring for these patients would increase substantially. The current state of development of the artificial heart provides an opportunity to collect data on investigational artificial heart performance, clinical results, patient status, and economic and social costs. This knowledge base would be invaluable for future technology assessments and policy decisions regarding third party reimbursement. Insofar as we may be faced with a multi-billion dollar annual investment in the future, detailed assessments of the artificial heart should be performed.

Assessing the artificial heart. The clinical moratorium revisited

Viewed in relation to the vast amount of clinical research in the United States, the number of total artificial heart (TAH) implants is so small as to be statistically invisible. And while the results of those implants to date may seem dubious in terms of the recipients' outcomes, theyare in fact very similar to those of many other innovative therapies when they are first tried ondesperately ill patients. Why, then, has the artificial heart been the object and subject of suchextraordinary interest and controversy? It has been the subject of special federal studies, reports, and hearings for 20 years; has been perceived and portrayed as a unique chapter in the annals of human experimentation and therapeutic innovation; has attracted medically unprecedented media attention; and, in the case of permanent implants, has received unusually exhaustive and restrictive regulatory supervision.

Evaluation of total artificial heart performance in man

This report describes the method whereby total artificial heart (TAH) performance was evaluated in the first human implantation, the operating characteristics of the TAH and the accompanying circulatory response. The patient survived for 112 days. Weekly averages (+/- standard deviation) for left-heart drive pressure ranged from 146 +/- 5 to 171 +/- 10 mm Hg, right-heart drive pressure from 46 +/- 4 to 79 +/- 17 mm Hg, heart rate from 77 +/- 8 to 98 +/- 3 beats/min, diastolic vacuum from 0 to 7 +/- 0.5 mm Hg and percent systole 40 +/- 1 to 44 +/- 0. Left-sided cardiac output ranged from 3.0 +/- 0.4 to 3.9 +/- 0.2 liters/min/m2, and was consistently greater than right-sided cardiac output, which ranged from 2.6 +/- 0.4 to 3.6 +/- 0.1 liters/min/m2. Drive line air pressure and flow signals and cineradiography of the TAH demonstrated complete filling and ejection for the left ventricle and complete filling but partial ejection for the right ventricle. There was no significant change in cardiac index during variation in right atrial pressure between 4 and 14 mm Hg. During 21 days of invasive hemodynamic monitoring, daily average of mean systemic arterial pressure ranged from 81 +/- 5 to 107 +/- 11 mm Hg, pulmonary artery pressure from 22 +/- 2 to 28 +/- 8 mm Hg and left atrial pressure from 8 +/- 2 to 22 +/- 4 mm Hg. Prominent V waves on the left atrial pressure tracing suggested mitral regurgitation as a cause of the difference between the outputs of the 2 ventricles.(ABSTRACT TRUNCATED AT 250 WORDS)

A theoretical right atrial pressure feedback heart rate control system to restore physiologic control to the rate-limited heart

Physiologic control of heart rate may be limited by sinus node injury or congenital conduction defects. Control theory may be applied to restore physiologic rate control. Mean right atrial pressure is a likely candidate for incorporation into an artificial control system because of its: (1) stability at rest; (2) tendency to increase during exertion in the rate-limited heart; (3) ability to decrease with increasing heart rate in the rate-limited heart; and (4) accessibility for measurement via the transvenous route. A theoretical right atrial pressure feedback heart rate control system is presented; applications to physiologic pacing of patients with sick sinus syndrome, rate control of the transplanted heart, and pump frequency control of the total artificial heart are discussed.

Clinical use of the total artificial heart

We report here our first experience with the use of a total artificial heart in a human being. The heart was developed at the University of Utah, and the patient was a 61-year-old man with chronic congestive heart failure due to primary cardiomyopathy, who also had chronic obstructive pulmonary disease. Except for dysfunction of the prosthetic mitral valve, which required replacement of the left-heart prosthesis on the 13th postoperative day, the artificial heart functioned well for the entire postoperative course of 112 days. The mean blood pressure was 84 +/- 8 mm Hg, and cardiac output was generally maintained at 6.7 +/- 0.8 liters per minute for the right heart and 7.5 +/- 0.8 for the left, resulting in postoperative diuresis and relief of congestive failure. The postoperative course was complicated by recurrent pulmonary insufficiency, several episodes of acute renal failure, episodes of fever of unidentified cause (necessitating multiple courses of antibiotics), hemorrhagic complications of anticoagulation, and one generalized seizure of uncertain cause. On the 92nd postoperative day, the patient had diarrhea and vomiting, leading to aspiration pneumonia and sepsis. Death occurred on the 112th day, preceded by progressive renal failure and refractory hypotension, despite maintenance of cardiac output. Autopsy revealed extensive pseudomembranous colitis, acute tubular necrosis, peritoneal and pleural effusion, centrilobular emphysema, and chronic bronchitis with fibrosis and bronchiectasis. The artificial heart system was intact and uninvolved by thrombosis or infectious processes. This experience should encourage further clinical trials with the artificial heart, but we emphasize that the procedure is still highly experimental. Further experience, development, and discussion will be required before more general application of the device can be recommended.