Long-term survival with a pneumatic artificial heart.
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Adult↗
Biomedical subjects
W S Pierce
Publications and source records attributed to W S Pierce.
Minimum power consumption of the electric ventricular assist device through the design of an optimal output controller.
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Assisted Circulation↗
Roller screw electric motor ventricular assist device.
The roller screw electric VAD is easier to manufacture and 25% lighter than the previously described drum cam model. This device requires 12 to 15 W to pump 6 to 8 l/min with minimal hemolysis. The motor drive has functioned for periods up to 93 days in vivo with no measurable wear. The compliance chamber volume varies by 100 cc during VAD function but does so while maintaining pressure variations below 15 mmHg. Compliance chamber volume loss of 2 to 5 cc/day is explained by gas transport through SPU. The subcutaneous sampling port provides ready access to the sealed system.
Animals↗
Clinical spectrum of mechanical circulatory assistance.
Mechanical blood pumps can provide effective circulatory support in a variety of clinical settings. Ventricular assist devices are single ventricle blood pumps designed to work in parallel with the natural heart. These devices can be powered by air pulses or an electric motor to provide temporary or permanent circulatory assistance, respectively. Unlike ventricular assist devices, artificial hearts replace the natural heart. In doing so, they provide complete support of both the systemic and pulmonary circulation. Air-driven artificial hearts will primarily support patients with profound biventricular failure prior to heart transplantation. Electrically assisted artificial hearts with their implantable energy converters are in the earliest stages of development. These devices will ultimately serve as permanent heart replacements in patients who do not qualify for heart transplantation.
Animals↗
Improving results in combined aortic and mitral valve replacement using cold potassium cardioplegia.
Our entire experience (33 patients) of combined aortic and mitral valve replacement was reviewed. In 20 patients, coronary perfusion with moderate hypothermia (28-32 degrees C) was used with 7 operative deaths (35% mortality). Catecholamines were used in 14 patients (70%). Potassium cardioplegia was used in 13 patients with no mortality (P less than 0.02) and use of catecholamines in only 4 (P less than 0.05). These data suggest that potassium cardioplegia is the method of preference for myocardial preservation for combined aortic and mitral valve replacement.
Aortic Valve↗
Right ventricular failure following implantation of a left ventricular assist device.
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Assisted Circulation↗
Aprotinin therapy for insertion of ventricular assist devices for staged heart transplantation.
Bleeding after insertion of ventricular assist devices is a common problem which carries a major risk of immediate and late complications. We evaluated the safety and efficacy of aprotinin in six patients undergoing staged heart transplantation and compared the results with those of six patients who received no aprotinin. The groups did not differ significantly with respect to age, gender, preoperative cause of cardiomyopathy, or cardiopulmonary bypass time. Patients treated with aprotinin had a significant reduction in postoperative chest tube drainage (743 +/- 457 versus 2036 +/- 1184 cc, respectively, for aprotinin therapy versus no therapy; p = 0.047). Blood transfusion requirements were reduced in patients treated with aprotinin (2.2 +/- 2.2 versus 10.7 +/- 7.1 U respectively, for aprotinin therapy versus no therapy; p = 0.038). No demonstrable serious side effects were attributed to the aprotinin treatment. We conclude that aprotinin is effective in reducing bleeding and transfusion requirements without increasing the incidence of clinically significant renal dysfunction or thromboembolic events.
Adult↗
Combined Registry for the Clinical Use of Mechanical Ventricular Assist Pumps and the Total Artificial Heart in conjunction with heart transplantation: sixth official report--1994.
BACKGROUND: The Combined Registry has existed since 1985 with a design toward the voluntary submission of data from centers undertaking mechanical circulatory assistance. METHODS: The compiled results of the Combined Registry for the Clinical Use of Mechanical Ventricular Assist Pumps and the Total Artificial Heart was reviewed and subjected to strict statistical evaluation. RESULTS: More than 2000 implanted devices have been reported through January 1994, and 584 of these have been placed with the intention of bridge to heart transplantation. Nearly 70% of these patients have subsequently undergone heart transplantation, and 69% of those patients have survived to discharge from the hospital. Outcome statistics continue to favor isolated left ventricular support, although only discharge rates are significantly improved over right (p = 0.01) or biventricular assistance (p < 0.001) and the total artificial heart (p < 0.001). Within the group of left ventricular devices no individual mode of support proved advantageous over the others for transplantation or discharge rates. The 30-day mortality for all devices is approximately 36%, which remains much higher than that for orthotopic heart transplants. Isolated left ventricular support, however, had a 30-day mortality of only 9% with similar improvement in 12- and 24-month survival. CONCLUSIONS: These data show the continued success with these devices for bridging critically ill patients to transplantation. Additionally, it supports the ongoing development of devices implanted for long-term use, which might replace orthotopic transplantation for those patients currently deemed marginal candidates.
Adolescent↗
Evaluation of the fibrinolytic system in calves implanted with an artificial heart and ventricular assist device.
Thromboembolism is a serious complication of prolonged use of intracirculatory devices such as total artificial hearts (TAH) and ventricular assist devices. The authors have evaluated alteration in the hemostatic system associated with long-term use of TAH and ventricular assist devices. This article reports results of a prospective evaluation of the fibrinolytic system in four calves implanted with TAHs and four with ventricular assist devices. Blood fibrinolytic activity measured with a solid phase radiometric assay was elevated in two of four TAH calves; plasma plasminogen activity was increased in three. Plasma plasminogen activator activity was undetectable (normal) in all animals. Slight to moderate hypofibrinogenemia was noted in all TAH calves. Calves implanted with a left ventricular assist device had mostly normal blood fibrinolytic activity, fibrinogen, and plasminogen levels. Fibrinogen survival was measured in two calves with ventricular assist devices and three with TAH and was in the normal range in all of these animals. No significant thrombotic lesions were noted at autopsy in five calves that died or were electively killed. These observations suggest enhanced activation of the fibrinolytic system in some calves implanted with a TAH. This may offer a measure of protection against thrombosis in some animals.
Animals↗
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. The chamber is made of Dacron velour covered segmented polyether polyurethane urea. The annular compliance chamber was evaluated in vitro by comparing pump balance control performance against that obtained with an open vent. In the CVP range of 5-12 mmHg, LAP was maintained within 1 mmHg of the values obtained with a vent. Studies continue to determine the range of volumes over which the chamber is effective, differences in rates of diffusion, and performance during changes in barometric pressure.
Atmospheric Pressure↗
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. The dynamic stroke volume is 60 ml, and the maximum output is 9 L/min. Pump output is automatically controlled to maintain full stroke volume as preload varies. Hall effect sensors for detecting rotary position of the motor are the only sensors used. Six bovine implants were performed, with durations of 84, 208, 244, 130, 70 (ongoing), and 15 (ongoing) days. Four animals used two-way telemetry, whereas the remaining two used one-way (outgoing) telemetry. These first chronic in vivo tests with the Penn State completely implanted LVAD system have demonstrated that it is a feasible solution to long-term ventricular support.
Animals↗
Results of mechanical ventricular assistance for the treatment of post cardiotomy cardiogenic shock.
The voluntary submission of data on patients who receive mechanical circulatory assistance for post cardiotomy cardiogenic shock and acute myocardial infarction has resulted in an established data base for the ongoing evaluation of these devices. Since its inception in 1985, there have been 1,279 cases reported of implanted ventricular assist devices for post cardiotomy cardiogenic shock. The average duration of support for these devices is approximately 4 days. Those patients who underwent implantation of a centrifugal pump had significantly shorter periods of support when compared with the pneumatically supported group. Patients had similar periods of support when comparing clinical outcome. Approximately 70% of the reported cases underwent centrifugal assistance. The majority of reported cases were supported with isolated left ventricular assistance. There was no significant difference in overall outcome statistics when comparing type or mode of support. Approximately 45% of reported patients were weaned from circulatory assistance, and 25% of all patients survived to discharge. These numbers remain consistent with previously reported statistics. The results with acute myocardial infarction remain limited. Of the 96 reported patients, 26% were weaned from support and only 11.5% survived to discharge. This report continues to support the use and research for advancement of these devices toward the treatment of post cardiotomy cardiogenic shock.
Adolescent↗
Bridging to transplant. Equal extended survival for patients undergoing LVAD support when compared with long-term medical management.
Implantation of ventricular assist devices (VADs) to support patients awaiting cardiac transplant has become an effective means of assuring that these critically ill patients survive to transplant. The authors undertook a retrospective analysis of 115 consecutive patients listed for cardiac transplant from January 1992 through June 1995. A VAD was implanted in 19 of these patients. Survival was calculated by intent to treat from the time of transplant listing through heart transplant, if it occurred. The analysis demonstrates that the patients who underwent implantation of a VAD as bridge to transplant had survival times similar to those of patients with medical management. These survival statistics demonstrate the utility of VADs as an effective means to bridge critically ill patients until a suitable donor organ becomes available. In addition, as previous studies have suggested for acute results, earlier implementation and better patient selection may lead to improved long-term survival.
Adult↗