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P M Portner

Publications and source records attributed to P M Portner.

At least 19 recordsLinked to original sources
PubMed1991

Clinical experience with the Novacor ventricular assist system. Bridge to transplantation and the transition to permanent application.

At Stanford University, a Novacor left ventricular assist system (Baxter Healthcare Corporation, Novacor Division, Oakland, Calif.) was placed as a bridge to heart transplantation in 13 patients. During the hospitalization preceding device implantation, all patients were receiving inotropic support for biventricular failure, 11 had pulmonary edema, 6 had life-threatening ventricular arrhythmias, 5 had liver dysfunction with coagulopathy, and 2 had renal failure necessitating artificial support. The mean cardiac index before implantation of the Novacor system was 1.5. All survivors with the Novacor device had a dramatic increase in cardiac output (mean cardiac index = 3.1). One patient with cardiac allograft rejection died during implantation of the left ventricular assist system. Two patients died of pulmonary sepsis and multiorgan failure after the device was implanted. All patients who had the Novacor device implanted for more than 7 days were able to walk and ride stationary bicycles while awaiting transplantation. Ten patients (77%) underwent successful heart transplantation after a mean of 18 days' support with the Novacor device. One patient died of presumed sepsis 2 days after transplantation. Nine patients (90%) are alive 4 months to 6 years after transplantation. In the overall United States experience, 68 patients (as of May 1990) have had a Novacor left ventricular assist device implanted. Five were still being supported, 39 had received a transplant (62%), and 35 patients (90%) survived the transplant hospitalization (1 died later). No instances of device failure have occurred. Overall, the Novacor assist system provided effective bridging to transplantation, with posttransplant survival similar to results after routine transplantation. Modifications and improvements based on this clinical experience have been made in the areas of patient selection, techniques of operative placement, postoperative management, and design of the assist system. Isolated left heart support with a fully implantable left ventricular assist system will be offered as an alternative to heart transplantation for selected patients by 1992.

Adolescent↗
PubMed1989

Implantable electrical left ventricular assist system: bridge to transplantation and the future.

An implantable left ventricular assist system (LVAS) utilizing an electromechanically driven dual pusher-plate blood pump has been employed in a multiinstitutional trial as a bridge to cardiac transplantation. Under development for permanent circulatory support in patients with end-stage heart disease, the LVAS, in this application, derives power and control from an external console via a percutaneous lead. The LVAS was implanted in 20 patients (16 men, 4 women) who were hemodynamically unstable or in refractory cardiogenic shock. The mean age was 44.9 years (range, 25 to 63 years). Preoperative diagnosis was evenly divided between end-stage ischemic disease, cardiomyopathy, and acute myocardial infarction. Implanted in the left upper quadrant within the anterior abdominal wall, the blood pump was connected between the left ventricular apex and ascending aorta. Total support of the systemic circulation and substantial left ventricular unloading were achieved with synchronous counterpulsation for periods up to 90 days (mean, 22.7 days). All patients were stabilized hemodynamically. The mean preoperative cardiac index of 1.5 L/min/m2 increased by a factor of 2. Pulmonary arterial pressures decreased substantially. Serious complications occurred in 16 patients, precluding cardiac transplantation in 10. Most complications (greater than 70%) were in patients who did not receive transplants; the most common complication was bleeding. Twelve of 13 patients with LVAS implants for more than seven days were mobilized, and 4 were fully ambulatory and completely rehabilitated. Orthotopic cardiac transplantation was performed in 10 patients after implants ranging from two to 90 days (mean, 30.3 days).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Isolated left ventricular assist as bridge to cardiac transplantation.

The electrically driven Novacor implantable left ventricular assist device has been implanted in six patients (four men and two women) since Sept. 7, 1984. In four of the six patients (67%) the device was a successful bridge to cardiac transplantation. One patient died of multiple organ failure and Candida sepsis after 16 days of support with the device. One patient died in the operating room of uncontrollable hemorrhage and biventricular failure caused by severe cardiac rejection. Three patients are alive with cardiac transplants 38, 17, and 10 months after transplantation. One patient died after cardiac transplantation of presumed sepsis. The Novacor left ventricular assist device performed in all cases without mechanical or electrical failure. Excluding the intraoperative death, assist duration ranged from 2 to 16 days. The cardiac index (synonymous with device output) ranged from 2.4 to 3.4 L/min/m2. No embolic events (cerebrovascular or systemic) occurred during assistance with the device. Minimal red cell hemolysis was documented during the period of support. The Novacor left ventricular assist device is a safe and effective bridge to cardiac transplantation in patients with refractory cardiogenic shock.

Adult↗
PubMed1983

The blood interface at artificial surfaces within a left ventricular assist system.

A left ventricular assist system presents a very complex set of interfaces to the blood. The interactions of the various components, their junctions, and fluid dynamic effects have been discussed at a macroscopic, cellular and molecular level. Failure of any part of the system can seriously compromise LVAS function or host response whether due to gross thrombosis with occlusion, proliferative PNI formation, or thromboembolic events. It has been stated that: "When artificial hearts are designed properly, nearly any surface goes." Unfortunately, the blood interface within any circulatory support system, and indeed in much simpler systems, is a much more complex function than design, which includes the surface, materials and many other factors (Table 6).

Adsorption↗
PubMed1978

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.

Animals↗
PubMed1978

An implantable permanent left ventricular assist system for man.

A new implantable, electrically powered LV AS suitable for long-term use in man has been designed and is under development. The system is based on the well developed high-efficiency pulsed solenoid technology and a careful a priori systems approach to integration of the energy converter with a suitable blood pump. A novel dual pusher-plate sac-type blood pump with significant advantages in hemodynamics, antithrombogenicity and durability has been designed. The complementary energy converter, a pivoted-armature dual-gap solenoid, addresses weaknesses in previous designs while retaining all the good features of its forerunners and provides for the first time a truly integrated implantable circulatory assist system for man.

Heart Ventricles↗
PubMed1976

An intrathoracic solenoid drive system for chronic left ventricular bypass.

The performance of an implantable Left Ventricular Assist System (LVAS), utilizing an advanced solenoid energy converter, has been extensively studied in vivo. For optimum system efficiency, reliability and responsiveness, the energy converter and blood pump are integrated into a single compact unit, which is implanted intrathoracically in an 80 Kg calf. The MK19 LVAS is battery operated and controlled by a miniature analog computer and is completely self-regulating. The maximum hemodynamic power provided by this circulatory assist system is 4 watts with cardiac outputs up to 10 L/min and a total system efficiency of 30%. LVAS function has been studied in a series of 19 calf experiments progressing through acute, model and chronic evaluations. Development of the implantation protocols and hemodynamic characterization were achieved in a series of 8 acute experiments. Long-term studies were conducted for periods up to 43 days in a series, including 2 control experiments using non-functional models and 9 functional LVAS chronic experiments. Aortic, left ventricular and left atrial pressures, pulmonary artery flow and pump outflow were monitored with chronically implanted transducers. A dedicated minicomputer provided real-time hemodynamic analysis and continuous surveillance of physiologic and LVAS parameters. In acute studies and in the immediate post-operative period of chronic experiments, synchronous LVAS operation reduced peak LV pressures to 30 mm Hg with cardiac outputs of 5 to 7 L/min. In chronic studies, with recovery of normal LV function, long-term synchronous operation was maintained, without capture of the total cardiac output and with significantly reduced ventricular unloading.

Animals↗
PubMedDate not supplied

Chronic ovine evaluation of a totally implantable electrical left ventricular assist system.

The totally implantable Novacor left ventricular assist system (LVAS) comprises a pump/drive unit (VAD), electronic control and power subsystem (ECP), variable volume compensator (VVC), and belt skin transformer (BST). The system is now undergoing chronic in vivo evaluation. Cumulative animal testing of VAD, VVC, and BST subsystems are 12.1, 4.9, and 43 years, respectively. The longest implants were 279 days for the VAD, 767 days for the VVC, and 1,148 days for the BST. A chronic implant of the total system was electively terminated at 260 days. The LVAS was powered via the BST. Continuously monitored hemodynamic and pump parameters have demonstrated normal hemodynamics and LVAS operation. Periodic VVC determinations suggest a 0.8 ml/day diffusive gas loss. Tether-free operation has been demonstrated with an Ag-Zn battery backpack. The animal was healthy and free of infection as indicated by routine hematologic, biochemical and serum enzyme determinations. Hemolysis is minimal (plasma free hemoglobin less than 5 mg%). Pump output ranged from 7 to 8 L/min. Severe valve calcification was the reason for elective termination at 260 days. This preclinical in vivo experience, and in vitro reliability studies, demonstrate efficacy of the total system.

Animals↗
PubMedDate not supplied

Initial clinical experience with a wearable controller for the Novacor left ventricular assist system.

The Novacor left ventricular assist system (LVAS), an implanted electromechanically driven blood pump, has been used in an ongoing clinical trial as a bridge to cardiac transplantation since 1984. The initial configuration included a console based extracorporeal controller. Because patients supported by the device usually become rehabilitated and highly mobile, a wearable control system was developed for the ambulatory patient. Ergonomically designed for portability, comfort, and appearance, it offers the recipient greater mobility, improved self-image, and an enhanced quality of life. This wearable control system consists of a microprocessor based compact controller that drives the implanted pump/drive unit in synchronous counterpulsation to the native heart. Main and reserve rechargeable power packs, each incorporating a "smart" monitoring circuit with charge-level display and alarm, are capable of supporting the pump for as long as 7 hr. An LVAS monitor can be connected to the controller for device monitoring and adjustment or as a power supply in lieu of the main power pack. Clinical evaluation in patients with end-stage heart disease followed the same protocol as the console study. By April 4, 1994, 41 patients had been supported by the wearable system, including 9 patients currently being supported. Mean duration of use was 51 days (range, 1.5-143+ days), compared with 42 days for 170 console patients (range, 0-370 days). Survival to transplant was 66%, which was similar to the survival (60%) for the patients using the console. Post-transplant survival was 100%, compared with 90% for console patients (not significantly different). After recovering from implant surgery and pre-implant morbidity, device recipients had considerable freedom and mobility and were able to move freely within and outside the hospital. Recipients could readily switch between monitored and untethered operation and could manage power pack replacement and recharging.

Adult↗
PubMedDate not supplied

Protocol for releasing Novacor left ventricular assist system patients out-of-hospital.

Between September 1984 and April 1995, the Novacor left ventricular assist system (LVAS) has provided more than 13,000 days of mechanical circulatory support to cardiac transplant candidates in the United States and Europe. The duration of support of these 312 patients has ranged between 1 and 370 days, with an average support of 40 days, including use of the console based system and the wearable system. Of this group, 21% have been supported for more than 60 days, with an average support of 118 days. We have seen that patients who have been supported for more than 30 days have recovered from the effects of LVAS implant surgery and have shown a potential for rehabilitation from morbid congestive heart failure. Few changes to the pump settings or the medical orders have been needed after the third postoperative week. The reliability of the LVAS and the degree to which patients can be rehabilitated suggest that restricting patients to a hospital environment is unnecessary. In addition, the increasing wait for a donor heart, the quality of life that can be achieved, and the high cost of inpatient care make it desirable to discharge patients from the hospital and allow them to await a donor heart in a more home-like setting.

Ambulatory Care↗
PubMedDate not supplied

A sophisticated electromechanical ventricular simulator for ventricular assist system testing.

With the advent of chronically implanted left ventricular assist systems, new adaptive control algorithms are being developed to allow automatic device control under a variety of hemodynamic conditions. An electromechanical pump is described that accurately mimics ventricular function. A pusher-plate sac pump with tri-leaflet valves is coupled to a high-speed linear motor. Pump chamber volume and pressure are constrained to follow the time-varying elastance model of ventricular function by use of a microprocessor feedback loop.

Computer Simulation↗
PubMedDate not supplied

Bovine pericardial valves. Nine-year clinical experience with the Novacor left ventricular assist system.

The Novacor electrically powered left ventricular assist system (LVAS), currently used in a bridge-to-transplant (BTT) clinical trial, incorporates bovine pericardial (BP) valves (Edwards CVS Division, Baxter Healthcare Corporation). In preclinical evaluation in the adult sheep, BP valves exhibited severe calcific stenosis as early as 8 weeks postimplant (longest implant 158 days, elective termination for calcific deposit). The clinical experience, however, has been in sharp contrast. Eighty-one patients have been supported for a cumulative duration of 9.1 years (two currently on LVAS). Thirty-five (43%) patients were supported for longer than 30 days, and of these, 29 (85%) were transplanted. The longest implant duration was 370 days (alive, 8 months posttransplant). There was no evidence of calcific degeneration of these valves for durations to 370 days. These results are encouraging for ultimate chronic clinical application.

Animals↗