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Biomedical subjects

W S Pierce

Publications and source records attributed to W S Pierce.

At least 199 records · Page 11Linked to original sources
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Testing of a 50 cc stroke volume completely implantable artificial heart: expanding chronic mechanical circulatory support to women, adolescents, and small stature men.

The development of a completely implanted total artificial heart at our institution has progressed to successful in vivo and in vitro testing of a device that is nearing clinical testing. This system consists of a 70 cc stroke volume pump originally designed to be used in men of average stature. Implantation of this system remains limited by patient size; hence, many women and adolescent patients will likely be precluded from support because of their smaller stature. A system similar in design, but with a 50 cc stroke volume pump has been developed. The first in vivo study of this device has been undertaken. A calf was supported for 33 days. The animal was extubated and ambulatory within the first 6 hours of implantation, and remained healthy until the thirty-third postoperative day when it suffered an embolic neurologic event. The pump and operating system worked flawlessly throughout the period of support. Further in vivo and in vitro testing will be undertaken. Development of a scaled down total artificial heart system expands this type of circulatory support to those critically ill patients previously deemed poor candidates because of their smaller body habitus.

Adolescent↗
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In vitro and in vivo evaluation of a right ventricular assist device.

A simple right ventricular assist device (RVAD) has been developed. This device will be useful in situations where biventricular failure has been partially treated by placement of a left ventricular assist device, or when right ventricular failure occurs in isolation. This pneumatically actuated, R-wave synchronized, sac type pump contains no valves, and is connected by a graft to the pulmonary artery. The RVAD was tested in a circulation simulator to verify its hemodynamic efficacy and then implanted in six calves for 2-4 weeks to evaluate its biocompatibility. In vitro testing of the RVAD demonstrated that it restored normal hemodynamics in the presence of severe simulated RVF. In six animal implantations, a small amount of thrombus was found in one pump. No anticoagulants were employed. Thrombus was present in the connecting graft in three animals; in two this was clearly related to technical implant errors. No evidence of significant hemolysis was found. This simple RVAD has been found to be hemodynamically effective, is simple to use, and is well tolerated. Refinements in the interconnection graft between the pulmonary artery and the device are necessary.

Animals↗
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Results of mechanical circulatory assistance before heart transplantation.

Between February 1984 and December 1987, 63 patients were accepted as candidates for heart transplantation. Eighteen patients (29%) required some form of mechanical circulatory support before transplantation; eight patients received an intraaortic balloon pump, five patients had left ventricular assist devices, two patients received biventricular assist devices, and in three patients the total artificial heart was implanted. Fourteen of the 18 patients underwent transplantation with seven longterm survivors.

Assisted Circulation↗
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Determinants of survival in patients with ventricular assist devices.

Mechanical ventricular assist devices (VADs) have led to survival in patients who develop postcardiotomy cardiogenic shock (PCCS) refractory to conventional therapies. To elicit determinants of survival, the authors reviewed records of 26 patients at our institution who required Pierce-Donachy VADs for PCCS. Thirteen patients were weaned from ventricular assistance (50%), nine (34.6%) achieved long-term survival, and 17 died. Survivors and those that died were equivalent in terms of age, sex, NYHA class, type of operation, and preoperative hemodynamics. Ventricular assist pumping was established earlier in survivors (P = 0.006) although aortic cross-clamp and total cardiopulmonary bypass times were equivalent between the groups. The development of biventricular failure was significantly associated with the inability to wean from mechanical circulatory assistance. Despite an equal incidence of biventricular failure, survivors had milder forms of this entity and all patients with severe biventricular failure requiring a biventricular assist device failed to wean and ultimately died (N = 5). Of all complications, inadequate cardiac output was a significant determinant of weaning. Perioperative myocardial infarction and renal failure were found to be univariate determinants of survival. Inadequate cardiac output and biventricular failure preclude weaning from mechanical circulatory assistance. Survival is associated with the expeditious establishment of assist pumping, and with the avoidance of irreversible perioperative myocardial injury and renal failure.

Acute Kidney Injury↗
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A permanent arterial access system.

Now that long-term survival can be achieved in animals with mechanical circulatory devices, reliable permanent arterial access for physiologic and pharmacologic studies has become important. A novel approach has been developed eliminating the need for repeated arterial cannulation. The arterial access system (AAS) consists of a 7 Fr Silastic catheter, which is threaded into the internal mammary artery, and an attached access well, which is placed in the subcutaneous tissue over the sixth rib. The AAS is implanted during the initial operation. The access well is punctured percutaneously with a 23 gauge needle to obtain arterial blood or to measure arterial pressure, and patency is maintained by flushing the access well with 2,000 U of heparin each week. The AAS was implanted in six calves (three with a total artificial heart, three with a ventricular assist device) for a mean duration of 124 days (range, 20-323 days). There were no infections related to the AAS, and none of them thrombosed. All of the AAS had excellent arterial wave forms when punctured. The AAS is simple to implant, provides reliable long-term arterial access, and does not appear to increase the risk of infection.

Animals↗
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Aortic rupture caused by fungal aortitis: successful management after heart transplantation.

A 26-year-old man with end-stage idiopathic cardiomyopathy was supported with a Pierce-Donachy left ventricular assist device for 31 days before orthotopic heart transplantation. Fungal endocarditis was discovered at the time of recipient cardiectomy, and antifungal therapy was begun. Fungal mediastinitis developed 4 days after transplantation and was treated with mediastinal irrigation. Massive mediastinal hemorrhage caused by fungal aortitis occurred on two occasions and was successfully treated with a bovine pericardial patch. The patient is well 9 months after transplantation.

Adult↗
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Bridge to heart transplantation: the Penn State experience.

At The Pennsylvania State University, we have performed four bridge-to-heart transplantation procedures in the past year. Two patients were supported with an LVAD, and two patients were supported with a TAH. One patient had a successful transplantation and remains well 10 months after operation; two patients died of sepsis after transplantation. A fourth patient has had a TAH in place for greater than 110 days and is currently awaiting transplantation. The problems that remain to be solved are developing strategies to minimize the risk of infection, defining the indications for use of an LVAD vs a BVAD vs a TAH, developing an effective regimen to prevent thromboembolism, and determining the proper interval for transplantation after the insertion of a mechanical pump as a bridge.

Adult↗
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Summary of the world experience with clinical use of total artificial hearts as heart support devices.

A review of the world experience with the implantation of total artificial hearts has been carried out. Thirteen centers throughout the world have implanted 27 total artificial hearts in 26 patients. Eight different types of total artificial hearts have been employed. As of June 1, 1986, five of these individuals have had implants for permanent support. Of the other twenty-one patients, three patients died while on a total artificial heart, seven patients died following transplantation, two patients are waiting for transplant, and nine patients have successfully been transplanted and are presently alive. Various clinical preoperative and postoperative parameters are analyzed in this investigation.

Adult↗
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The artificial heart--1986: partial fulfillment of a promise.

While certain critically ill patients who are awaiting cardiac transplantation can be stabilized with either drugs, the intraaortic balloon pump, or a left ventricular assist device, other patients do not respond to these therapies and the use of a safe and effective artificial heart can be lifesaving. For this latter group, the pneumatic heart appears to be suitable, although minor improvements will be welcomed. The percutaneous tubes and bulky drive unit are not great disadvantages to the patient who uses an interim heart and remains in a constant care area. The patient with end-stage heart disease who cannot have a heart transplant has little hope at present. Interestingly, the pneumatic heart that is available now might be an acceptable alternative to death if the incidence of stroke could be overcome. In the future, these patients will be better served by either an electrically powered left ventricular assist pump or a totally artificial heart.

Adult↗