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Biomedical subjects

V L Poirier

Publications and source records attributed to V L Poirier.

33 records · Page 2Linked to original sources
PubMedDate not supplied

An ambulatory, intermediate term left ventricular assist device.

A portable, percutaneous, battery-operated left ventricular assist device intended for intermediate and long-term use is described. The system performed satisfactorily in vitro for periods of up to 9 months and in vivo for periods in excess of 3 months. Long-standing hypertension was observed in a 98 day implant with accompanying renal and visceral vascular changes. No evidence of peripheral thromboembolism was seen. Examination of the textured blood pump surface revealed an established biologic lining, characteristic of that previously seen in calves with some evidence of peripheral calcification.

Ambulatory Care↗
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Extended clinical support with an implantable left ventricular assist device.

Clinical evaluations are under way of an intracorporeal (abdominally positioned) pulsatile left ventricular assist device (LVAD) that is capable of providing support for extended periods (greater than 30 days) in patients awaiting heart transplantation. The LVAD, developed by Thermo Cardiosystems Inc. (Woburn, MA), has uniquely textured blood contacting surfaces and requires only minimal antithrombotic therapy. It has been used at the Texas Heart Institute as a bridge to transplantation in 11 patients, including 2 who are currently receiving support. Four patients required extended LVAD support (35-132 days); of those, three are doing well at 1.5, 8.5, and 13 months, respectively, after transplantation, and one died of liver failure 49 days after transplantation. The LVAD was operated in a fixed-rate mode to maintain pump flows at 4-8 L/min, resulting in stabilization of hemodynamic and secondary organ function in all patients. Blood chemistry and hematologic values returned to normal during LVAD support in three of four patients. Postoperative anticoagulation was gradually reduced over the course of the trials. The two most recent patients (35 and 132 days) received only oral dipyridamole (75 mg X 3/day) and aspirin (80 mg/day) after the early recovery period (four-six days), resulting in normal prothrombin and partial thromboplastin times. Plasma hemoglobin levels remained within acceptable limits, and there was no evidence of thromboembolism. Blood contacting surfaces were coated with a thin, adherent, biologically derived lining. The initial results indicate that the intracorporeal LVAD, with textured blood contacting surfaces, can effectively support the failing heart for extended periods (greater than 30 days) with minimal antithrombotic therapy.

Adult↗
PubMedDate not supplied

Clinical responses to ventricular assistance versus transplantation in a series of bridge to transplant patients.

Hemodynamic and peripheral organ responses to ventricular assistance were compared with transplantation in a cohort of patients bridged with the HeartMate 1000 IP left ventricular assist device (LVAD) (Thermo Cardiosystems Inc., Woburn, MA). The study population included 27 patients that were supported an average of 102 days (range, 15-324 days). Two hepatic (total bilirubin and serum glutamic oxaloacetic transaminase [SGOT]) and two renal (creatinine and blood urea nitrogen [BUN]) parameters were measured: 1) before LVAD insertion, 2) 30 and 60 days during ventricular assistance, 3) before transplantation while still on the VAD, and 4) 30 and 60 days after transplantation. Total bilirubin values were significantly greater just before LVAD implant (2.3 mg/dl) than before transplantation (0.7 mg/dl). Although there was no difference after 30 days of either treatment, the total bilirubin values were greater at 60 days after transplantation (1.1 mg/dl) than at an equivalent time on the LVAD (0.6 mg/dl). The SGOT values were also significantly reduced before transplantation. No differences at 30 and 60 days after either procedure were noticed. Creatinine and BUN values were greater before LVAD implant (1.7 and 37 mg/dl) than before transplantation (1.2 and 19 mg/dl). The creatinine values were also greater after transplantation at 30 and 60 days (2.0 and 1.6 mg/dl) than at comparable intervals after LVAD implantation (1.0 and 1.2 mg/dl), presumably as a result of the use of immunosuppressive drugs. End organ function was markedly improved while on the device, enhancing the physiologic status of the patients before transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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The quest for a solution. We must continue. We must push forward. The 16th Hastings Lecture.

The development of an artificial heart and heart assist devices has been ongoing for several decades. Great progress has been achieved leading to the safe and effective support of patients with end stage cardiac disease. Although patients can now live at home with a high quality of life, much work is left to be done. With the majority of technical problems behind us, we must now overcome the economic, regulatory, and acceptance barriers. We must continue, we must push forward to make these systems available for our fellow human beings.

Heart, Artificial↗
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Use of a left ventricular assist device in an outpatient setting.

The vented electric Heartmate LVAD (VE-LVAD) (Thermo Cardiosystems, Inc., Woburn, MA) is a reliable, fully portable system that allows selected patients with end-stage cardiomyopathy to undergo outpatient treatment while waiting for heart transplantation. This implantable, pusher-plate LVAD is actuated by an electric motor located within the pump housing. The patient wears external batteries and a system controller, which power and control the LVAD motor through a percutaneous lead. Since May 1991, four men have been supported with the VE-LVAD. They ranged in age from 33 to 50 years (mean, 44.3 years); two had idiopathic cardiomyopathy, and two had ischemic cardiomyopathy. Of the four patients, three underwent support of 196, 219, and 504 days; support in the fourth patient is ongoing at more than 90 days. All four patients were fully rehabilitated to New York Heart Association Class I status. Because they were well and fully mobile, the protocol was amended to allow these patients to leave the hospital in a four phase program that begins with 16 hr day passes and leads to hospital discharge. When patients leave the hospital, they are accompanied by trained family members or friends. The patients who have participated in the program have performed routine activities, attended social events, and spent the night at home. The VE-LVAD system seems safe and appropriate for the outpatient setting in selected patients. Patients have been able to manage the system without assistance from medical or engineering personnel. This initial positive experience with outpatient LVAD treatment demonstrates the potential for providing long-term cardiac support with this type of implantable technology.

Activities of Daily Living↗
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Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and Society of Thoracic Surgeons: long-term mechanical circulatory support system reliability recommendation.

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.

Clinical Trials as Topic↗
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HeartMate III: pump design for a centrifugal LVAD with a magnetically levitated rotor.

A long-term, compact left ventricular assist device (LVAD), the HeartMate III, has been designed and fabricated, featuring a centrifugal pump with a magnetically levitated rotor. The pump has been optimized by in vitro testing to achieve a design point of 7 L/min against 135 mm Hg at high hydrodynamic efficiency (30%) and to be capable of up to 10 L/min under such a load. Furthermore, the pump has demonstrated no mechanical failures, low hemolysis (4-10 mg/dl plasma free Hb), and low thrombogenicity during six (40, 27, 59, 42, 27, and 49-day) in vivo bovine studies.

Animals↗
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LVADs--a new era in patient care.

Clearly, a challenge exists in treating end stage congestive heart failure patients. Drug therapy is not effective and too few donor hearts prevent transplantation from being the therapy of choice. The only alternative that is developing is the use of LVAD technology. Patients can benefit with an improved quality of life as well as increased longevity. Physicians can benefit by providing their patients with an effective alternative with the potential of reversing the disease process. Costs are significant; however they are comparable in comparison to other treatment arms. With increased use, costs will reduce as the result of developing the efficient use of this technology.

Equipment Design↗
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Can our society afford mechanical hearts?

Congestive heart failure afflicts 4 million people in the United States, with 400,000 deaths annually. Very little can be done for individuals with this condition, which is increasing in prevalence. The only hope is the promise of intervention with permanent circulatory support systems. Can we as a society afford the $3.1 billion that would be required to support every patient needing such a system? This cost represents an increase of 1/2 of 1% of the $662 billion per year expended for medical care. Fortunately, circulatory support systems do not necessarily represent an expense, but rather an investment that has a reasonable payback period. An investment in an individual of $100,000 for the device and implantation cost, coupled with an ongoing maintenance cost of $4,000 per year, can return to society an income greater in value than the investment. The payback period is strongly dependent on the earning power of the individual, as well as the amount of medical attention or complications experienced. An individual with an annual salary of $40,000 per year becomes a positive financial force in our society and increases the gross national product (GNP) within 5 years. The same individual with extensive medical complications and intermittent loss of salary can extend the payback period by an additional 2 years. Circulatory support systems have the potential of increasing our GNP, leading to a higher standard of living for the populace.

Health Care Costs↗
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Development of a polyurethane percutaneous access device for long-term vascular access.

The percutaneous placement of intravascular devices creates a portal for microbial invasion that can result in local infections or septicemia. In nature, resistance to "exist site" infection in percutaneous organs, such as teeth, is prevented by a dense collagen/epithelial barrier. A new percutaneous access device has been developed that incorporates a porous polyurethane "button" at the subdermal level. This device promotes the development of a collagen/epithelial interface, thus inhibiting sinus formation. Twelve percutaneous access devices (PCADS) were implanted in calves; eight devices were utilized for venting of, and hard wire passage to, an implantable left ventricular assist device (LVAD) and served as controls. Four devices were utilized for long-term vascular access. The PCADS remained in situ for 2-127 days (mean 70). Excellent healing was apparent in all cases, and no exit site or catheter related infections occurred. Histologic examination demonstrated fibroblastic in-growth and collagen deposition within the porous polyurethane, which provides a barrier to epithelial migration and firmly anchors the device. These PCADS appear to reduce exit site infections and may improve upon currently available long-term vascular access catheters.

Animals↗