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Biomedical subjects

W S Pierce

Publications and source records attributed to W S Pierce.

At least 19 recordsLinked to original sources
PubMed1992

Platelet and fibrinogen survival in calves implanted with artificial heart and ventricular assist device--correlation with autopsy findings.

The two main ingredients of blood clots formed on artificial surface are platelets and fibrinogen. In this study, we measured platelet and fibrinogen survival in calves implanted with total artificial heart (TAH) and left ventricular assist device (LVAD), and correlate these data with autopsy findings. Platelet survival with autologous 111In-labeled platelets was performed on nine calves implanted with TAH and five with LVAD. Fibrinogen survival with 131I-labeled homologous fibrinogen was performed on six calves with TAH and three with LVAD. Platelet survival was significantly shortened in both groups of animals: 5.89 +/- 0.52 days, control 6.46 +/- 0.31 days, p = 0.0013; fibrinogen survival was normal: 8.79 +/- 1.20 days, control 8.64 +/- 1.16 days. At autopsy two calves with TAH had multiorgan thromboembolism. Two other animals with TAH and four with LVAD had focal renal infarcts. Most animals had minor clot formation within the prosthetic device. Major septic complications occurred in four calves with TAH and one with LVAD. Continuous platelet activation by artificial surface probably explains the shortened platelet survival and thromboembolic complications.

Animals↗
PubMed1992

Hematologic and hemostatic complications associated with long-term use of total artificial heart: clinical and experimental observations.

The two most serious complications associated with long-term use of a total artificial heart (TAH) are thromboembolism and infection. In this article, we review our experience in one patient implanted with a pneumatic TAH for 396 days, and in 24 calves implanted with the same type of device for 70 to 353 (median 150) days. During his survival with the TAH, our patient suffered several thromboembolic episodes despite adequate anti-coagulation with warfarin. Autopsy showed widespread thrombotic lesions, mostly in the brain. Throughout his survival, the patient had markedly elevated plasma beta-thromboglobulin and fibrinopeptide A levels, indicating sustained activation of platelets and the coagulation system secondary to blood contact with the artificial surface. Long-term use of TAH in calves causes significant mechanical hemolytic anemia and a small reduction in the total leukocyte and neutrophil counts. The platelet count normalized to preimplantation levels by 25 to 35 weeks. At autopsy, thrombotic lesions and organ infarction were noted in 13 calves, and major septic complications were documented in 10 animals. Although impressive gains in the clinical and experimental use of TAH were achieved during the last 15 years, thromboembolism and infection remain challenging problems.

Anemia, Hemolytic↗
PubMed1992

Ventricular assist devices for postcardiotomy cardiogenic shock. A combined registry experience.

Data submitted voluntarily to the combined registry since its inception in 1985 to December 31, 1990, on the use of ventricular assist devices for postcardiotomy cardiogenic shock in 965 patients were analyzed. Approximately 45% of patients were weaned from temporary circulatory assistance and 24.6% reached hospital discharge regardless of the original operation. In 90% of patients who were discharged from the hospital, circulatory support was able to be discontinued by 1 week. Rates of weaning and discharge were statistically different and favored those patients requiring univentricular support only. Results were equal whether nonpulsatile centrifugal or pulsatile pneumatic devices were used for support. Although complications were frequent and multiple during assist pumping, patient variables including age greater than 70 years rather than direct complications caused by circulatory support were likely to affect overall outcome. In patients achieving hospital discharge, 2-year actuarial survival was 82% with 86% of patients being in New York Heart Association functional class I or II. In rare instances of device dependency in 43 patients (4.5%) with no contraindications to transplantation, 32 (74.4%) underwent bridge to cardiac transplant and 20 (62.5%) were discharged. This multi-institutional experience would continue to support the use of ventricular assist devices in postcardiotomy cardiogenic shock.

Adolescent↗
PubMed1990

An electric artificial heart for clinical use.

Advances in microelectronics, high-strength magnets, and control system design now make replacement of the heart using an implantable, electrically powered pump feasible. The device described herein is a compact, dual pusher plate unit with valved polyurethane sac-type ventricles positioned at either end. The power unit consists of a small, brushless direct current motor and a motion translator. A microprocessor control system is used to regulate heart beat rate and provide left-right output balance. Bench studies lasting for as long as 1 year have been performed. Heart replacement with the electric heart has been performed in 18 calves since 1984. The longest survivor lived for more than 7 months. Among the causes of termination were component failure, thromboembolic complications, and bleeding. No major problem has been identified that precludes prolonged use of the electric heart. In the future the patient with end-stage heart disease will have an electric artificial heart as one therapeutic option.

Animals↗
PubMed1990

Vascular responses to dopamine and dobutamine in the awake calf during constant aortic flow or constant aortic pressure.

We investigated vascular effects of dopamine and dobutamine infusions in awake calves implanted with the Penn State total artificial heart (TAH). This preparation uniquely permits independent servo-control of cardiac output (CO) and arterial blood pressure (BP). Thirty-two studies (22 with dopamine and 10 with dobutamine) were performed in four juvenile calves from 1 to 4 months after TAH implantation. Studies were performed in one of two TAH operating conditions: (a) constant aortic flow, in which the CO is fixed and aortic BP varies with systemic vascular resistance (SVR), or (b) constant pressure, in which the CO varies to maintain a constant BP when SVR changes. During both constant flow and constant pressure studies, dopamine caused a dose-dependent increase and dobutamine caused a dose-dependent decrease in SVR. There was no difference in the SVR response between constant flow or constant pressure conditions at any dose of dopamine or dobutamine (p greater than 0.05). The infusion doses of dopamine required to raise the SVR 20 and 50% during constant flow studies were 7.2 and 12.4 micrograms.kg-1.min-1, respectively. In constant pressure studies, these doses were 7.7 and 13.5 micrograms.kg-1.min-1. The infusion dose of dobutamine resulting in a 20% reduction in SVR was 27.2 micrograms.kg-1.min-1 in constant flow studies 26.2 micrograms.kg-1.min-1 in constant pressure studies. These data suggest that baroreflex and other indirect mechanisms are less important than direct vascular drug effects in this system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Permanent circulatory support systems at the Pennsylvania State University.

Permanent circulatory support systems are required for patients in whom myocardial damage is irreversible and cardiac transplantation is not possible. Two systems are described which provide long term circulatory support: the left ventricular assist system and the total artificial heart. These systems are based on the design of a pusher plate actuated blood pump, driven by a small brushless dc electric motor and rollerscrew driver. An implantable motor controller maintains suitable physiologic flow rates for both systems and controls left-right balance in the total artificial heart. Other parts of the system include an intra-thoracic compliance chamber, transcutaneous energy and data transmission system, and internal and external batteries.

Animals↗
PubMed1989

Current status of permanent total artificial hearts.

Pneumatic total artificial heats, although demonstrating utility as temporary mechanical circulatory support devices, have not demonstrated a great deal of promise as permanent cardiac replacements. The increasing number of patients who would be candidates for total heart replacement suggests a large role for a permanent implantable total artificial heart. To that end, the Pennsylvania State University is developing an electric motor-driven total artificial heart; the results with implants in calves are encouraging. In this device, a roller-screw mechanism is used to translate the rotation of a brushless direct-current motor into rectilinear motion of a pusher-plate assembly, which in turn empties the blood sacs. The total artificial heart of the future will function under automatic control without percutaneous leads, and this should provide the patient with a nearly normal life-style. Although further experimental efforts are necessary to prepare the device for clinical trials, the technology to provide a safe and reliable electric blood-pump system is at hand.

Animals↗
PubMed1989

Mortality of coronary artery bypass grafting before and after the advent of angioplasty.

In an effort to determine whether the population of patients undergoing isolated coronary artery bypass grafting and the outcome of these operations have changed, we analyzed the records of two patient populations from our institution. Interventional cardiology techniques (angioplasty, thrombolysis) were not used at our institution before 1982. The records of 736 patients (group 1) who underwent isolated coronary artery bypass grafting from January 1975 to July 1981 were reviewed and compared with a group of 603 patients (group 2) who underwent operation from July 1985 to December 1987. The techniques of operation and myocardial preservation were virtually identical during the two periods. During the group 2 analysis period, 343 angioplasty procedures were performed. The patients in group 2 were significantly older, had increased preoperative New York Heart Association classification, had sustained more previous myocardial infarctions, and had more associated morbid medical conditions. There was a threefold increase in patients seen for reoperative revascularization procedures and a fourfold increase in emergency operations. Overall mortality, although not significantly different, did increase slightly from 2.69% in group 1 to 3.83% in group 2. Mortality after elective procedures remained essentially unchanged (2.05% for group 1 and 1.90% for group 2).

Aged↗
PubMed1989

Toward an implantable artificial heart. Experimental and clinical experience at The Pennsylvania State University.

The number of patients who would be candidates for replacement of their failing native heart with an artificial device increases every year. A multidisciplinary group at The Pennsylvania State University is working toward the development of a reliable, totally implantable artificial heart. Initial work resulted in a pneumatic total artificial heart that has performed well in animal implants and has been used clinically in three patients as a temporary bridge to cardiac transplantation. Although pneumatic total artificial hearts have demonstrated utility as temporary mechanical circulatory support devices, attempts at permanent implantation by other groups have been fraught with complications. Because of the suboptimal performance of the pneumatic devices used for permanent implantation, the authors' groups at Penn State is developing n electric motor-driven total artificial heart with encouraging results in calf implants. This artificial heart of the future will use a transcutaneous energy transmission system that will obviate the need for percutaneous lines. Thus, the patient will be provided with as near a normal life-style as possible. At present the technology is at hand to implant an electric blood pump system that should provide a reasonable life-style and function reliably with minimal care. Ongoing cooperative experimental efforts will help to provide the answers necessary to make this system ready for clinical use.

Animals↗
PubMed1989

Hemostatic abnormalities in two patients implanted with total artificial hearts.

Patients implanted with total artificial hearts (TAH) suffer frequent thromboembolic complications. The authors report results of continuous monitoring of multiple hemostatic parameters and autopsy findings in two patients implanted with TAH. Case 1 who used a TAH for 10 days and then underwent orthotopic transplantation died of fungal infection 7 days later. At autopsy, mycotic and nonmycotic thrombi were found in the brain, kidneys, spleen, and large bowel. Case 2, who survived 396 days with a TAH, suffered multiple thrombotic episodes despite adequate anticoagulation with warfarin. Autopsy revealed widespread thrombotic lesions mostly in the brain and lungs. Both patients had markedly elevated plasma beta-thromboglobulin and fibrinopeptide A levels throughout their survival, indicating sustained activation of platelets and coagulation secondary to blood contact with artificial surface. Other factors such as infection, liver damage, and acute pancreatitis might have also contributed to activation of hemostasis. As used in the authors two patients, antiplatelet drugs and warfarin seem to be ineffective in preventing artificial heart-related thromboembolic complications.

Adult↗
PubMed1988

Heterotopic prosthetic ventricles as a bridge to cardiac transplantation. A multicenter study in 29 patients.

Heterotopic prosthetic ventricles were used to support the circulation in 29 candidates for heart transplantation who were expected to die before procurement of a donor heart. Twenty-one of these patients (average age, 36 years) underwent successful transplantation after 8 hours to 31 days of circulatory support. The other eight patients died because their condition could not be stabilized for transplantation, despite restoration of blood flow. Fourteen patients received biventricular support; 15 received only left ventricular support, with pharmacologic assistance of right heart function. Before transplantation, blood flow from the left prosthetic ventricle averaged 2.8 +/- 0.4 liters per minute per square meter of body-surface area, and from the right prosthesis 2.4 +/- 0.4 liters, as compared with an average flow of 1.6 +/- 0.5 liters per minute per square meter before implantation. Of the 21 patients who received heart transplants, 20 were discharged from the hospital after a median of 31 days. Nineteen patients were alive at 7 to 39 months, and 11 of the first 12 were alive at one year. We conclude that heterotopic placement of prosthetic ventricles as a bridge to transplantation provides an effective method of temporarily supporting cardiac function in critically ill patients without removing the natural heart. The early survival rate after transplantation is similar to that with elective cardiac transplantation.

Adolescent↗