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Biomedical subjects

R L Kormos

Publications and source records attributed to R L Kormos.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

Effects of long-term Novacor artificial heart support on blood rheology.

This study presents characteristics of hemorheology for six patients during long-term support (85-144 days) on a Novacor left ventricular assist device (LVAD) as a bridge-to-cardiac transplantation. Results indicate that a certain "baseline" rheology can be identified in patients whose support was uneventful. However, in the patients who had one or more neurologic episodes during support, these events were associated with altered hemorheology, including increases in plasma and relative blood viscosity, and red cell rigidity.

Blood Proteins↗
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Influence of panel-reactive antibody and lymphocytotoxic crossmatch on survival after heart transplantation.

Review of 463 heart transplants was undertaken to examine the relationship between level of panel-reactive antibody (PRA) and a standard donor-specific lymphocytotoxic crossmatch (LXM) on the incidence of death from hyperacute, acute, and chronic rejection. Death from chronic rejection was defined as being caused by graft atherosclerosis. Hyperacute rejection was diagnosed in 18 allografts, and only two recipients had PRA greater than 10% and another two a positive LXM. Five-year actuarial freedom from death caused by all forms of rejection correlated with PRA values as follows: PRA 0% to 10% (415 patients), 85%; PRA 11% to 25% (29 patients), 68%; PRA greater than 25% (19 patients), 57% (p less than 0.005). Additionally, there was a positive linear relationship between PRA and duration of acute rejection episodes in the first 3 months after transplantation. A positive retrospective donor-specific LXM was present in 42 of 401 patients; most of them (32 patients) were low positive (10% to 50% cell death), and none could be correlated with antibody specificity toward donor HLA antigens. Five-year actuarial freedom from death caused by rejection was 83% in those with a negative LXM, 74% in those with low-positive, and 79% in those with high-positive LXM (p = NS). Negative LXM result did not reduce the risk of death caused by rejection in any of the PRA subgroups. While PRA greater than 10% is a risk factor for rejection-related events, a negative LXM in patients with an elevated PRA does not reduce the risk of death resulting from acute or chronic rejection.

Actuarial Analysis↗
PubMedDate not supplied

Increased perioperative lung preservation injury with lung procurement by Euro-Collins solution flush.

In 47 donor organ procedures for heart-lung transplantations, lungs were preserved by autoperfusion in 21 cases and by Euro-Collins solution flush in 26 cases. Criteria used to diagnose inadequate allograft function included radiographic interstitial and alveolar infiltrates and an alveolar-arterial oxygen gradient significantly greater than 100 mm Hg at 24 hours after surgery. Oxygen gradients were calculated intraoperatively, on arrival in the intensive care unit, and during the first 24 hours after surgery. With these criteria, 15 patients with perioperative preservation damage were identified. They were compared with 32 patients without evidence of preservation injury. Patients with preservation injury showed persistently elevated alveolar-arterial oxygen gradients that were significantly above noninjury values at all times (p less than 0.03). There was no difference in donor organ ex vivo time between the two groups (227.8 +/- 74.4 vs 169.5 +/- 76.9, p = NS). The incidence of perioperative preservation injury was significantly greater among patients in the Euro-Collins solution group (12/26) than in patients with autoperfusion (3/21) (p = 0.04, Fisher's exact test). Three of the 15 recipients died of primary lung graft failure. In our hands, preservation by use of a modified Euro-Collins solution flush technique has led to unpredictable results in lung transplantation.

Adolescent↗
PubMedDate not supplied

Monoclonal versus polyclonal antibody therapy for prophylaxis against rejection after heart transplantation.

Between August 1986 and December 1987, 88 patients received either RATG or OKT3 for immunoprophylaxis before heart transplantation. By the end of the first month after transplantation, 25% of the patients who received RATG had experienced a rejection episode compared with 43% of those receiving OKT3. This difference was persistent as many as 4 months after transplantation. While 50% of the OKT3 patients had a second episode of rejection, only 35% of the RATG patients did so. Randomization of these agents was complicated by severe cardiopulmonary side effects attributed to the first dose of OKT3. Five hours after the first dose of OKT3, a 25% drop in mean arterial pressure, accompanied by significant hypoxia, was seen in a majority of patients. There was no difference in the incidence of infection between the two groups.

Antibodies, Monoclonal↗
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Comparative trial of immunoprophylaxis with RATG versus OKT3.

A randomized trial of rabbit antithymocyte globulin (polyclonal) versus OKT3 monoclonal antibody prophylaxis was carried out in 82 heart transplant recipients, who, in addition, received baseline immunosuppression with cyclosporine, azathioprine, and prednisone. One-year actuarial survival was comparable between groups (95% to 98%), but the likelihood of histologic rejection within the first 30 days of transplant was more than seven times greater in OKT3 patients (0.58/patient vs 0.08/patient). Patients receiving OKT3 were more likely to have repeated episodes of rejection, and the mean time to rejection for patients receiving OKT3 was shorter (33 days) than for patients receiving rabbit antithymocyte globulin (67 days). At 120 days, while 52% of patients receiving rabbit antithymocyte globulin were free of rejection, versus 37% of the OKT3 patients, the difference was not significant. There was no difference in the incidence of major or minor bacterial or viral infection between groups, but significant hemodynamic side effects were seen after the first dose of OKT3, and aseptic meningitis developed in two OKT3 patients.

Animals↗
PubMedDate not supplied

Biomaterial associated impairment of local neutrophil function.

The effect of biomaterials on neutrophil function was studied in vitro to determine if these materials activated neutrophils and to determine the subsequent response of these neutrophils to further stimulation. Two biomaterials--polyurethane, a commonly used substance, and Velcro pile (used in the Jarvik 7 heart)--were evaluated. Two control substances, polyethylene and serum-coated polystyrene, were used for comparison. Neutrophil superoxide release was measured following incubation with these materials for 10, 30, and 120 min in the absence of additional stimulation and after stimulation with formylmethionylleucylphenylalanine (fMLP) or phorbol myristate acetate (PMA). The authors observed that the incubation of neutrophils on both polyurethane and Velcro resulted in substantially increased superoxide release that was greater after the 10 min than after the 30 or 120 min association. These activated neutrophils exhibited a poor additional response to fMLP but responded well to PMA. The effect of implantation of the Novacor left ventricular assist device on peripheral blood neutrophil function was also evaluated. The peripheral blood neutrophils exhibited normal superoxide release and chemotaxis. These studies suggest that biomaterials may have a profound local effect on neutrophils, which may predispose the patient to periprosthetic infection, but that the reactivity of circulating neutrophils is unimpaired.

Artificial Organs↗
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Influence of the donor lung on development of early infections in lung transplant recipients.

Infection of the lung allograft is the greatest cause of morbidity and mortality after heart-lung transplantation. To better understand the pathogenesis of these infections, we compared the results from cultures of the donor tracheas with the type and prevalence of early intrathoracic infections in the recipients. In the last 37 recipients, intrathoracic infections occurred within 2 weeks of operation in 16 (43%). Organisms isolated from the donor tracheal cultures were different from those associated with early infections, except for three of four recipients with heavy growth of Candida in donor tracheal cultures, in whom fatal invasive candidiasis developed caused by the same species of Candida isolated from the donor culture. Comparisons were made between recipients with (n = 16) and without early infection (n = 21) for age of donors and recipients, ischemic time, length of donor stay in an intensive care unit, donor arterial oxygen pressure, duration of recipient intubation, sterile donor tracheal culture or culture with presence of mouth flora, bacterial pathogens, or Candida, method of lung preservation, and antibiotic prophylaxis of donor. The only factor significantly associated with the onset of early infection was the presence of mouth flora in the donor tracheal culture (p = 0.004, Fisher's exact test, two sided). Multiple logistic regression was performed to test the additional contribution of other covariates after adjusting for the presence of mouth flora. None of the other covariates contributed to the occurrence of early infection. Recipients with early infection had a significantly lower survival compared with those without early infection (p = 0.04) by the Kaplan-Meier survival analysis.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMedDate not supplied

Artificial heart. Hemorrheology and transient ischemic attacks.

Hemorrheology was studied in patients undergoing artificial heart support as a bridge-to-cardiac transplantation. Abnormal hemorrheology was seen in two patients, one on a Jarvik-7 total artificial heart, and the other on a Novacor left ventricular assist device. Both of these patients suffered neurologic episodes. The rheology of these two patients coincided well with their clinical status, and was accompanied by marked increases in relative blood viscosity, erythrocyte rigidity, fibrinogen concentration, and platelet aggregation. Results show that improving hemorrheology may be a beneficial avenue to pursue in preventing or treating transient ischemic attacks or other complications in patients during support with mechanical devices.

Blood Flow Velocity↗
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Novacor left ventricular assist filling and ejection in the presence of device complications.

In order to better understand the relationship among certain device related complications and Novacor left ventricular assist system (LVAS) pumping parameters, a Mock Circulatory Loop was utilized to simulate the following clinically realistic conditions: 1) inflow valve regurgitation, 2) inflow cannula obstruction, 3) outflow valve regurgitation, and 4) outflow cannula obstruction. Various pumping parameters (e.g., pump rate, stroke volume, pump output) were recorded at baseline (control) and during each simulation. Additionally, pump volumes were continuously recorded and differentiated for calculation of rates of pump filling (FR) and ejection (ER). The results indicate that perfusion pressures and rates of filling and ejection change significantly in the presence of device complications. The implications of these findings, as relates to assessment of pump operation in LVAS patients, are discussed.

Blood Volume↗
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Early and late tamponade with the Novacor left ventricular assist system.

Cardiac tamponade can be a major complication after implantation of the Novacor left ventricular assist system (LVAS). Between 1987 and 1989, 14 patients received an LVAS as a bridge to cardiac transplantation: 3 developed early tamponade (33 +/- 12 hr postoperatively) and 5 were diagnosed with a late tamponade (9.4 +/- 3.2 days postoperatively). One patient had both early and late tamponade. Early tamponade was more common in those with increased perioperative blood loss (5,270 +/- 1,942 ml vs. 1,420 +/- 1,160 ml in other patients, p less than 0.05). Early tamponade was suggested by reduction in mean arterial pressure (74 +/- 1 to 64 +/- 3 mmHg), LVAS output (5 +/- 0.5 to 2.7 +/- 0.7 L/min), LVAS stroke volume (55 +/- 4 to 23 +/- 5 ml), and an increase in central venous pressure (13 +/- 1 to 21 +/- 1 mmHg, p less than 0.05 for all values). Late tamponade was associated with a marked rise in central venous pressure (14 +/- 1 to 22 +/- 2 mmHg, p less than 0.05), with only a mild decrease in LVAS output (4.9 +/- 1 to 3.8 +/- 0.9 L/min) and stroke volume (49 +/- 8 to 36 +/- 3 ml), without a significant change in mean arterial pressure. Two of these five late episodes occurred in patients who were anticoagulated with heparin (PTT 52 and 100 sec), and in one other with warfarin (PT 27 sec, PTT 55 sec); two patients were not on any anticoagulants. Surgical drainage of pericardial effusions, and especially of clotted blood found frequently posterior to the left ventricle in the space created by the LVAS decompressed left ventricle, resulted in an immediate return of all hemodynamic measurements to normal in both early and late tamponade.

Adult↗
PubMedDate not supplied

LVAS pump performance following initiation of left ventricular assistance.

Prevention of disturbed flow (e.g., flow stasis) and consequent thrombosis in heart pumps is based upon design characteristics determined during laboratory bench tests. These tests employ optimal filling and emptying characteristics, such as the full-fill to complete empty mode in the Novacor left ventricular assist system. Filling characteristics of the Novacor LVAS were examined during the first 48 hours after implantation in 14 patients. Fill volume of the pump was reduced in pathologic states, such as cardiac tamponade, and following the initiation of right ventricular mechanical circulatory support. In addition, multiple regression analysis revealed that right ventricular function measured by the amount of inotropic support required, the right ventricular ejection fraction, and the total pulmonary resistance, significantly predicted left ventricular assist pump fill volume during the first 48 hours of support. Flow visualization simulating these clinical conditions of incomplete filling suggest inadequate valve washing, particularly around the inlet valve and its conduit, which may predispose to thrombus formation.

Cardiac Output↗
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Heart transplantation in patients with malignant disease.

We have traditionally pushed the limits of conservative candidate criteria for heart transplantation. We have been gratified by our results in the aged, the diabetic, and the mortally ill. Our inclusion of patients with malignant disease underscores our philosophy to include patients as candidates for transplantation for whom the procedure has reasonable expectation of success. We report here our early results of heart transplantation in 11 patients with malignant disease. Our survival rate in this group is 100%, and all patients are leading active lives with no evidence of recurrent or metastatic tumor. Immunosuppression protocols were adjusted on an individual basis determined by the chemotherapy dosage, duration, and relation to transplantation. Whenever possible a 1-year disease-free interval after completion of adequate cancer therapy is desired before transplantation.

Adult↗
PubMedDate not supplied

Posttransplantation diabetes mellitus in heart transplant recipients.

This study was undertaken to investigate the impact of diabetes, which develops after heart transplantation, on infection and patient survival. Nondiabetic patients (366) underwent heart transplantation at our institution between June 1, 1980 and January 12, 1988. Of these patients, 29 (8%) developed posttransplantation diabetes (PTD), defined as a continued need for hypoglycemic agents. The PTD group did not differ significantly from the nondiabetic recipients in age, sex, or human leukocyte antigen type. The average age in the PTD group was 49 years. Average length of follow-up was 21 months (range 4 to 46 months). Eighteen patients are maintained on insulin. Eight patients are on oral hypoglycemic agents. Three patients died while on insulin. The average prednisone dosage in this group is 0.23 mg/kg/day. There have been 18 minor infections and four potentially serious nonlethal infections in the 27 PTD recipients. One lethal infection occurred 33 months after heart transplantation. The only other fatality was related to metastatic bladder cancer. This lethal infection rate of 3% compares with a rate of 11% in all nondiabetic recipients who have follow-up for 21 months. The 3-year actuarial survival of the PTD group is 75%, which compares favorably with the survival of nondiabetic patients. PTD cannot be predicted by sex, age, or human leukocyte type before transplantation, and it does not significantly increase the incidence of mortality or serious infection.

Coronary Angiography↗
PubMedDate not supplied

Use of the total artificial heart as an interim device: initial experience in Pittsburgh with four patients.

The experimental use of the total artificial heart as an interim device before heart transplantation has demonstrated its potential usefulness. Once again there has been a reaffirmation of the basic principle in transplantation that careful selection of patients is a prerequisite for a high likelihood of success. Our experience suggests that advanced degrees of renal failure and liver dysfunction are not likely to be associated with a consistently useful interim support. Although our numbers of patients are quite small, we continue to be concerned by what appears to be the tendency for the development of severe thrombocytopenia not resulting from the use of heparin. Studies of platelet kinetics and deposition are planned for the future. Although no recipient has had direct evidence of thromboembolic events, systemic anticoagulation with heparin has been aggressively applied, and bleeding complications have been common. All Jarvik-7 hearts on which autopsies have been performed have demonstrated grossly evident platelet fibrin thrombi, especially around the inlet and outlet valve housings. It has not been our purpose to investigate the relative role for univentricular or biventricular assist. It is likely that a number of our patients might have benefited from left ventricular assistance alone. It would appear that additional patients are needed before strong conclusions can be formed regarding the potential benefits and risks of the current Jarvik-7 device or any total artificial heart as an interim method of support before heart transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Assessment of the response of right ventricular performance to decreasing levels of mechanical assistance by on-line pressure area relationships.

The rapid assessment of the response of right ventricular (RV) performance to decreasing levels of mechanical assistance may be an important adjunct in determining if a patient can tolerate the removal of such a device. This report describes the use of on-line pressure area relationships to assess RV function in a patient supported with an RV assist device (RVAD). Mid RV short axis cross-sectional area was measured on-line by transesophageal echocardiography with an automated endocardial border detection feature. RV pressure was measured with a high fidelity catheter. Pressure and area were plotted simultaneously on a computer workstation interfaced with the pressure and echo systems to yield on-line pressure area loops. The following indices of RV performance were calculated while RVAD flow was decreased in 1 L/min increments: stroke work' (SW' = integral of PdA)[mmHg*cm2], stroke area (SA = Maximum Area-Minimum Area)[cm2], and fractional area change (FAC = SA/Maximum Area*100)[%]. SW', SA, and FAC significantly increased with decreasing RVAD flow: SW'(from 32 to 61 mmHg*cm2), SA (from 2.58 to 4.37 cm2), and FAC (from 20 to 32%). In conclusion, the increase in these parameters of RV performance with decreasing mechanical assistance suggested that this patient would tolerate removal of the RVAD, which was subsequently successful. This method of on-line pressure area relationships may be useful to predict the need for further mechanical assistance.

Analog-Digital Conversion↗