Feasibility of a Composite Measure of Pulmonary Vascular Impedance and Application to Patients with Chronic RV Failure Post LVAD Implant

Pulmonary vascular impedance (PVZ) describes RV afterload in the frequency domain and has not been studied extensively in LVAD patients. We sought to determine (1) feasibility of calculating a composite (c)PVZ using standard of care (SoC), asynchronous, pulmonary artery pressure (PAP) and flow (PAQ) waveforms; and (2) if chronic right ventricular failure (RVF) post-LVAD implant was associated with changes in perioperative cPVZ.PAP and PAQ were obtained via SoC procedures at three landmarks: T(1), Retrospectively, pre-operative with patient conscious; and T(2) and T(3), prospectively with patient anesthetized, and either pre-sternotomy or chest open with LVAD, respectively. Additional PAP's were taken at T(4), following chest closure; and T(5), 4-24 h post chest closure. Harmonics (z) were calculated by Fast Fourier Transform (FFT) with cPVZ(z) = FFT(PAP)/FFT(PAQ). Total pulmonary resistance Z(0); characteristic impedance Zc, mean of cPVZ(2-4); and vascular stiffness PVS, sum of cPVZ(1,2), were compared at T(1,2,3) between +/-RVF groups.Out of 51 patients, nine experienced RVF. Standard hemodynamics and changes in cPVZ-derived parameters were not significant between groups at any T.In conclusion, cPVZ calculated from SoC measures is possible. Although data that could be obtained were limited it suggests no difference in RV afterload for RVF patients post-implant. If confirmed in larger studies, focus should be placed on cardiac function in these subjects.

Psychosocial Assessments and Outcomes in Organ Transplantation

A qualitative review was conducted to define the term psychosocial as applied to transplant patients and to summarize evidence regarding the role and impact of psychosocial assessments and outcomes across the transplant process. English-language case series and empirical studies from January 1970 through April 1990 that were abstracted in Medline and Psychological Abstracts or listed in publications' bibliographies were used as data sources. A qualitative analysis was performed to determine the depth of the case reports and whether the empirical reports obtained statistically reliable, clinically significant findings. The authors conclude that psychosocial assessments differ in content and application to candidate selection depending on the transplant program. Psychosocial status before transplant does not consistently affect medical outcomes after transplant. Psychosocial status generally improves with transplant, although difficulties are prevalent in psychological adjustment and in compliance with medical regimens. Psychiatric history can predict psychological outcomes after transplant but does not consistently predict compliance. Social supports and coping strategies strengthen psychosocial outcomes. Posttransplant psychosocial outcomes may predict physical morbidity and mortality.

Gender differences in patterns of emotional distress following heart transplantation

The study provides the first empirical evaluation of gender differences in psychological symptomatology and DSM-III-R major depressive disorder (MDD) across the first year following heart transplantation. An important goal was to identify physical health-related and psychosocial factors that could account for, or mediate, any association between gender and psychological distress. The sample for the present analyses was drawn from a larger cohort of 172 heart recipients and included all 28 women in the cohort plus 118 men who were matched demographically with the group of women. Detailed patient assessments were completed at 2, 7, and 12 months posttransplant. As expected, women's symptom levels were consistently higher than men's. However, while men's symptom levels in all areas declined with time posttransplant, women's distress in the area of depression initially improved but then worsened by the 12-month assessment. The distribution of episodes of MDD showed a temporal pattern of gender differences similar to that of depressive symptoms. The most important mediators of the gender-depression relationship were factors related to early posttransplant daily functional limitations: women reported more impairments in daily activities. Higher levels of such impairments, in turn, predicted subsequently higher depression levels by 12 months posttransplant. Several additional variables pertaining to transplant-related concerns and a low sense of personal mastery-while not serving as mediators-exerted their own independent effects on 12-month depression levels. The findings are relevant to the tailoring of educational and clinical interventions to the individual needs of women and men who receive heart transplants.

Alemtuzumab induction prior to cardiac transplantation with lower intensity maintenance immunosuppression: one-year outcomes

Induction therapy with alemtuzumab (C-1H) prior to cardiac transplantation (CTX) may allow for lower intensity maintenance immunosuppression. This is a retrospective study of patients who underwent CTX at a single institution from January 2001 until April 2009 and received no induction versus induction with C-1H on a background of tacrolimus and mycophenolate. Those with C-1H received dose-reduced calcineurin inhibitor and no steroids. A total of 220 patients were included, 110 received C-1H and 110 received no induction. Recipient baseline characteristics, donor age and gender were not different between the two groups. Mean tacrolimus levels (ng/mL) for C-1H versus no induction: months 1-3 (8.5 vs. 12.9), month 4-6 (10.2 vs. 13.0), month 7-9 (10.2 vs. 11.9) and month 10-12 (9.9 vs. 11.3) were all significantly lower for the C-1H group, p < 0.001. There were no differences between the C-1H and no induction groups at 12 months for overall survival 85.1% versus 93.6% p = 0.09, but freedom from significant rejection was significantly higher for the C-1H group, 84.5% versus 51.6%, p < 0.0001. In conclusion, induction therapy after CTX with C-1H results in a similar 12 month survival, but a greater freedom from rejection despite lower calcineurin levels and without the use of steroids.

Trajectories of change in quality of life in 12-month survivors of lung or heart transplant

Survival and functional outcomes for lung transplant recipients continue to lag behind those for heart recipients. Whether these poorer physical outcomes translate into poorer quality of life (QOL) for lung recipients relative to heart recipients is unknown. Lung versus heart transplant recipients' perceptions of QOL were longitudinally compared at three time-points across the first year posttransplant. Additionally, potentially important predictors of patient QOL were examined. Adult transplant recipients (N = 199) participated in semi-structured interviews that included measures of QOL, optimism, mastery, social support, religiosity and coping. Temporal patterns of QOL change were compared between lung and heart recipients who survived until 1 year posttransplant using mixed-model, hierarchical analysis of variance (ANOVA). Demographic and psychosocial predictors were examined with multiple regression analysis to identify the unique effects of each variable on QOL 1 year posttransplant. While heart recipients' QOL across several domains was higher shortly after transplant, lung patients' QOL improved and was equivalent to that of heart recipients by 1 year posttransplant. Greater optimism and support from friends predicted better QOL in physical, psychological and social domains. Conversely, avoidant coping strategies predicted poorer physical functioning. Thus, while clinical interventions designed to improve QOL posttransplant should be tailored to transplant recipients' initial psychosocial assets and liabilities, they need not be distinguished by transplant type.

Quality of life outcomes after heart transplantation in individuals bridged to transplant with ventricular assist devices

BACKGROUND

Increasing numbers of individuals receive ventricular assist devices (VADs) as bridges to heart transplantation. Physical morbidity risks and benefits, and quality of life (QOL) during VAD support have been documented. Effects of pre-transplant VAD support on functional and QOL outcomes after transplantation have received no empirical attention.

METHODS

Sixty-three VAD patients who received heart transplants underwent QOL evaluations of physical functioning, emotional and cognitive well-being, and social functioning at 2, 7, and 12 months after transplant (response rate = 95%). Ninety patients who had not received VADs--matched to the VAD group on cardiac-related and sociodemographic characteristics--served as longitudinal controls.

RESULTS

Both VAD and non-VAD groups showed similar levels and similar, statistically significant (p < 0.05) improvement in physical functioning (sleep, body care, mobility, ambulation, overall functional status, number of somatic complaints) across the study period. Emotional well-being (elevated depressive, anxiety, and anger symptoms; post-traumatic stress disorder rate) was stable or improved in both groups, and VAD patients showed significantly lower anxiety rates. The VAD patients' post-transplant cognitive status was significantly poorer. The VAD patients were significantly less likely to return to employment; other social functioning measurers (daily concerns, interpersonal activities/involvement, role function) showed mixed effects. Cognitive impairment explained much of the association between VAD support and post-transplant employment.

CONCLUSIONS

Although post-transplant physical and emotional recovery is similar in VAD and non-VAD patients, VAD patients retain more cognitive impairment and show mixed changes in social functioning. Increased attention to strategies to maximize VAD patients' cognitive capacity is required to facilitate social reintegration.

Blood biocompatibility analysis in the setting of ventricular assist devices

Ventricular assist devices (VADs) are increasingly applied to support patients with advanced cardiac failure. While the benefit of VADs in supporting this patient group is clear, substantial morbidity and mortality occur during the VAD implant period due to thromboembolic and infective complications. Efforts at the University of Pittsburgh aimed at evaluating the blood biocompatibility of VADs in the clinical, animal, and in vitro setting over the past decade are summarized. Emphasis is placed on understanding the mechanisms of thrombosis and thromboembolism associated with these devices.

Downregulation of matrix metalloproteinases and reduction in collagen damage in the failing human heart after support with left ventricular assist devices

BACKGROUND

Left ventricular assist device (LVAD) support of the failing heart induces salutary changes in myocardial structure and function. Matrix metalloproteinases (MMPs) are increased in the failing heart and are induced by stretch in cardiac cells in vitro. We hypothesized that mechanical unloading may affect LV plasticity by regulating MMPs and their substrates.

METHODS AND RESULTS

LV samples were collected from patients with dilated cardiomyopathy (DCM, n=14) or ischemic cardiomyopathy (ICM, n=16) at the time of implantation of the LVAD and again during cardiac transplantation. MMP-1, -3, and -9 were measured by ELISA, MMP-2 and -9 gelatinolytic activity by gelatin zymography, and tissue inhibitors of metalloproteinases (TIMPs) by Western blot. Total soluble and insoluble collagens were separated by pepsin solubilization, and the contents were determined by quantification of hydroxyproline. The undenatured soluble collagen was measured by Sircol collagen assay. The results showed that MMP-1 and -9 were decreased, whereas TIMP-1 and -3 were increased, but there was no change in MMP-2 and -3 and TIMP-2 and -4 after LVAD support. The undenatured collagen was increased, with the ratio of undenatured to total soluble collagens increased in ICM and that of insoluble to total soluble collagens increased in DCM after LVAD support.

CONCLUSIONS

The reduced MMPs and increased TIMPs and ratios of undenatured to total soluble collagens and insoluble to total soluble collagens after LVAD support suggest that reduced MMP activity diminished damage to the matrix. These changes may contribute to the functional recovery and LV plasticity after LVAD support.

The role of diastolic pump flow in centrifugal blood pump hemodynamics

We tried to verify the hypothesis that increases in pump flow during diastole are matched by decreases in left ventricular (LV) output during systole. A calf (80 kg) was implanted with an implantable centrifugal blood pump (EVAHEART, SunMedical Technology Research Corp., Nagano, Japan) with left ventricle to aorta (LV-Ao) bypass, and parameters were recorded at different pump speeds under general anesthesia. Pump inflow and outflow pressure, arterial pressure, systemic and pulmonary blood flow, and electrocardiogram (ECG) were recorded on the computer every 5 ms. All parameters were separated into systolic and diastolic components and analyzed. The pulmonary flow was the same as the systemic flow during the study (p > 0.1). Systemic flow consisted of pump flow and LV output through the aortic valve. The ratio of systolic pump flow to pulmonary flow (51.3%) did not change significantly at variable pump speeds (p > 0.1). The other portions of the systemic flow were shared by the left ventricular output and the pump flow during diastole. When pump flow increased during diastole, there was a corresponding decrease in the LV output (Y = -1.068X + 51.462; R(insert)(2) = 0.9501). These show that pump diastolic flow may regulate expansion of the left ventricle in diastole.

Relapsing bacteremia in patients with ventricular assist device: an emergent complication of extended circulatory support

BACKGROUND

Ventricular assist devices (VAD) are currently approved for use as a bridge for transplantation. Although reports have suggested acceptable rates of survival of patients with VAD, there is little information regarding the mechanism and etiology of bacteremia in these patients.

METHODS

We prospectively followed patients who underwent VAD implantation and developed bacteremia during VAD support at the University of Pittsburgh Medical Center. Relapsing bacteremia was defined as at least two episodes of positive blood cultures with a genetically related organism on 2 different days. Species identification and susceptibility testing were performed on all isolates. Pulse field gel electrophoresis was performed on selected blood and VAD isolates.

RESULTS

Between January 1998 and August 1999, 3 patients with VAD developed relapsing bacteremia, which was treated with full courses of antibiotic agents, 2 of whom also developed VAD endocarditis. All 3 patients had documented driveline or device pocket infections with these isolates. Consecutive blood and VAD isolates were found to be genetically related within each patient.

CONCLUSIONS

These patients with bacteremia after VAD implantation had relapse due to the same strain, which may have originated from indolent driveline infection. Endovascular infection in this setting is difficult to eradicate with antibiotic agents and carries a high mortality. These patients should be considered to have priority for orthotopic heart transplantation.

Prevalence and risk of depression and anxiety-related disorders during the first three years after heart transplantation

Although poor psychological adjustment to organ transplantation appears to be a major contributor to reduced quality of life and increased physical morbidity, the prevalence and risk factors for psychiatric disorder have not been considered beyond the first 12-18 months after transplantation. The authors enrolled a representative sample of 191 heart transplant recipients in a prospective examination of the prevalence, clinical characteristics, and risk factors for DSM-III-R major depressive disorder (MDD), generalized anxiety disorder (GAD), associated adjustment disorders, and posttraumatic stress disorder related to transplant (PTSD-T) during the 3 years postsurgery. Survival analysis indicates that cumulative risks for disorder onset were MDD, 25.5%; adjustment disorders, 20.8% (17.7% with anxious mood); PTSD-T, 17.0%; and any assessed disorder, 38.3%. There was only one case of GAD. PTSD-T onset was limited almost exclusively to the first year posttransplant. Episodes of MDD (but not anxiety disorders) that occurred later posttransplant (8 to 36 months postsurgery) were more likely than early posttransplant episodes to be treated with psychotropic medications. For both MDD and anxiety disorders, later episodes were less likely to be precipitated by transplant-related stressors than other life stressors. Factors increasing cumulative risk for psychiatric disorder posttransplant included pretransplant psychiatric history, female gender, longer hospitalization, more impaired physical functional status, and lower social supports from caregiver and family in the perioperative period. Risk factors' effects were additive; the presence of an increasing number of risk factors bore a dose-response relationship to cumulative risk of disorder.

Database: relevant or not

Progress in the field of ventricular assist devices requires a more rigorous and systematic method of collecting outcomes data. A worldwide registry of device implants and results is proposed. With widespread participation, data from this registry would improve the identification of risk factors and complications, and allow for the creation of predictive models that would enhance patient selection. Professional societies should lead the development of a registry in close partnership with government and industry. Data collection using the Web, with rigorous security measures to protect patient privacy, would offer numerous advantages in efficiency and immediacy of communication for all participants.

HeartMate II left ventricular assist system: from concept to first clinical use

The HeartMate II left ventricular assist device (LVAD) (ThermoCardiosystems, Inc, Woburn, MA) has evolved from 1991 when a partnership was struck between the McGowan Center of the University of Pittsburgh and Nimbus Company. Early iterations were conceptually based on axial-flow mini-pumps (Hemopump) and began with purge bearings. As the project developed, so did the understanding of new bearings, computational fluid design and flow visualization, and speed control algorithms. The acquisition of Nimbus by ThermoCardiosystems, Inc (TCI) sped developments of cannulas, controller, and power/monitor units. The system has been successfully tested in more than 40 calves since 1997 and the first human implant occurred in July 2000. Multicenter safety and feasibility trials are planned for Europe and soon thereafter a trial will be started in the United States to test 6-month survival in end-stage heart failure.

Psychosocial assessments and outcomes in organ transplantation

A qualitative review was conducted to define the term psychosocial as applied to transplant patients and to summarize evidence regarding the role and impact of psychosocial assessments and outcomes across the transplant process. English-language case series and empirical studies from January 1970 through April 1990 that were abstracted in Medline and Psychological Abstracts or listed in publications' bibliographies were used as data sources. A qualitative analysis was performed to determine the depth of the case reports and whether the empirical reports obtained statistically reliable, clinically significant findings. The authors conclude that psychosocial assessments differ in content and application to candidate selection depending on the transplant program. Psychosocial status before transplant does not consistently affect medical outcomes after transplant. Psychosocial status generally improves with transplant, although difficulties are prevalent in psychological adjustment and in compliance with medical regimens. Psychiatric history can predict psychological outcomes after transplant but does not consistently predict compliance. Social supports and coping strategies strengthen psychosocial outcomes. Posttransplant psychosocial outcomes may predict physical morbidity and mortality.

Relationship of blood pressure and pump flow in an implantable centrifugal blood pump during hypertension

The purpose of this study was to evaluate the real time relationship between pump flow and pump differential pressure (D-P) during experimentally induced hypertension (HT). Two calves (80 and 68 kg) were implanted with the EVA-HEART centrifugal blood pump (SunMedical Technology Research Corp., Nagano, Japan) under general anesthesia. Blood pressure (BP) in diastole was increased to 100 mm Hg by norepinephrine to simulate HT. Pump flow, D-P, ECG, and BP were measured at pump speeds of 1,800, 2,100, and 2,300 rpm. All data were separated into systole and diastole, and pump flow during HT was compared with normotensive (NT) conditions at respective pump speeds. Diastolic BP was increased to 99.3+/-4.1 mm Hg from 66.5+/-4.4 mm Hg (p<0.01). D-P in systole was under 40 mm Hg (range of change was 10 to 40 mm Hg) even during HT. During NT, the average systolic pump flow volume was 60% of the total pump flow. However, during HT, the average systolic pump flow was 100% of total pump flow volume, although the pump flow volume in systole during HT decreased (33.1+/-5.7 vs. 25.9+/-4.0 ml/systole, p<0.01). In diastole, the average flow volume through the pump was 19.6+/-6.9 ml/diastole during NT and -2.2+/-11.1 ml/diastole during HT (p<0.01). The change in pump flow volume due to HT, in diastole, was greater than the change in pump flow in systole at each pump speed (p<0.001). This study suggests that the decrease of mean pump flow during HT is mainly due to the decrease of the diastolic pump flow and, to a much lesser degree, systolic pump flow.

Continuously maintaining positive flow avoids endocardial suction of a rotary blood pump with left ventricular bypass

This study showed the usefulness of maintaining positive pump flow to avoid endocardial suction and as an assist bypass. Three calves were implanted with centrifugal pumps. Hemodynamics and pump parameters were measured at varying pump speeds (from 1,100 to 2,300 rpm). In each test pump, speed was adjusted to create 3 hemodynamic states: both positive and negative flow (PNF), positive and zero flow (PZF), and continuously positive flow (CPF). The pump flow volume was determined during systole (Vs) and diastole (Vd). Vs in PNF was 29.6 ml and was not significantly different from Vs in PZF (p > 0.15). Vd in PNF was significantly different from Vd in PZF (p < 0.05). All bypass rates of PNF were over 30% of pulmonary flow. All PZF bypass rates were between the PNF rate and the CPF rate. These data showed that PZF satisfied the minimum requirement of assist flow and was under 100% bypass. Thus, PZF may avoid endocardial suction.

Standardized ejection fraction as a parameter of overall ventricular pump function

To evaluate the pump function of the ventricle, a parameter which (i) incorporates systolic and diastolic function and (ii) separates the heart from preload and afterload is needed. This study utilized ejection fraction (EF), calculated from the end-systolic (ES) and end-diastolic (ED) pressure-volume relationship (PVR) using an arbitrary set of loading conditions. Ten isolated canine hearts with a balloon placed inside the left ventricle were used to determine the ESPVR and EDPVR. An end-diastolic volume (EDV) at a pressure of 15 mmHg and an end-systolic volume (ESV) at 70 mmHg were obtained from the EDPVR and ESPVR, respectively. EF was calculated as (EDV-ESV)/EDV. With low-dose (8 microg/min) and high-dose (40 microg/min) dobutamine infusion, the EF increased from 0.25+/-0.16 to 0.33+/-0.13 and 0.57+/-0.08 (p<0.01), respectively, in conjunction with increases in end-systolic elastance from 3.11+/-0.83 to 3.48+/-1.08 and 5.38+/-1.91 mmHg/ml (p<0.01). It was thus concluded that because the estimation of EF separates the heart from preload and afterload, this method may facilitate comparing overall pump function of hearts beating under different loading conditions.

Cardiac transplantation in survivors of lymphoma: a multi-institutional survey

BACKGROUND

Cardiac transplantation has been successfully performed in patients with a history of presumably cured Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). Though the risk of recurrence is a major concern, the long-term influence of prior cancer and cancer therapy on posttransplant outcome has not been previously investigated.

METHODS

Questionnaires were sent to 130 cardiac transplant centers in the United States registered with the United Network for Organ Sharing. Data collected included patient demographics; type, stage, and timing of HD/NHL; treatment for HD/NHL; posttransplant immunosuppressive regimen, rejection history, and outcomes; and Epstein-Barr virus status.

RESULTS

Thirty-four cardiac transplant recipients with a previous history of HD (n=16) or NHL (n=18) were identified. HD patients averaged 41+/-15 years of age, with a mean disease-free interval of 15+/-9 years at the time of transplantation. NHL patients averaged 42+/-17 years of age with a mean disease-free interval of 10+/-9 years at the time of transplantation. The mean follow-up for the entire group was 50 months (range, 2 days to 136 months), and mean follow-up for the survivors was 67 months (range, 23-136 months). The 1-, 3-, 5-, 7-, and 10-year actuarial survival estimates for the entire group are 77%, 64%, 64%, 64%, and 50%, respectively. Actuarial survival was lower in HD patients (P=0.04) and in patients who had previously undergone splenectomy (P=0.008). Cox regression analysis identified only prior splenectomy (P=0.02) as an independent risk factor for mortality after cardiac transplantation with an adjusted relative risk of 6.2 (1.7-21.9, 95% confidence intervals).

CONCLUSIONS

Although the numbers are small, these data strongly suggest that there is an increased mortality risk for cardiac transplant recipients with prior HD who have undergone splenectomy.

Human factors issues in ventricular assist device recipients and their family caregivers

Ultimately, for ventricular assist devices (VADs) to be acceptable as permanent alternatives to heart transplantation, patients' and their families' satisfaction with specific features and risks of VADs must be addressed. Of 42 eligible patients who received VADs between February of 1996 and December of 1998, we interviewed 37 patients (17 Novacor, 18 Thoratec, 2 with both devices) and 20 of their primary family caregivers about device related concerns and reactions. Demographic and health related correlates of respondents' concerns were examined. Eleven patients discharged from the hospital with the VAD in place were then reinterviewed 1 month after discharge. At baseline, patients' general perceptions of the VAD were positive, although 22-52% reported specific concerns, including most often worry about infection (52%), difficulty sleeping due to the position of the driveline (52%), pain at the driveline exit site (46%), worry about device malfunction (40%), and being bothered during the day by device noise (32%). The prevalence of most concerns rose with duration of VAD support. Caregivers' perceptions did not differ significantly from patients' perceptions. Outpatients were somewhat more concerned than inpatients about device noise and risk of stroke, but were markedly less concerned about infection. Across all patients, higher levels of device related concerns were correlated with more physical functional limitations and more psychological distress, and reduced quality of life. Demographic characteristics and device type were not uniformly related to device concerns.

A clinical trial combining donor bone marrow infusion and heart transplantation: intermediate-term results

BACKGROUND

Donor chimerism (the presence of donor cells of bone marrow origin) is present for years after transplantation in recipients of solid organs. In lung recipients, chimerism is associated with a lower incidence of chronic rejection. To augment donor chimerism with the aim to enhance graft acceptance and to reduce immunosuppression, we initiated a trial combining infusion of donor bone marrow with heart transplantation. Reported herein are the intermediate-term results of this ongoing trial.

METHODS

Between September 1993 and August 1998, 28 patients received concurrent heart transplantation and infusion of donor bone marrow at 3.0 x 10(8) cells/kg (study group). Twenty-four contemporaneous heart recipients who did not receive bone marrow served as controls. All patients received an immunosuppressive regimen consisting of tacrolimus and steroids.

RESULTS

Patient survival was similar between the study and control groups (86% and 87% at 3 years, respectively). However, the proportion of patients free from grade 3A rejection was higher in the study group (64% at 6 months) than in the control group (40%; P =.03). The prevalence of coronary artery disease was similar between the two groups (freedom from disease at 3 years was 78% in study patients and 69% in controls). Similar proportions of study (18%) and control (15%) patients exhibited in vitro evidence of donor-specific hyporesponsiveness.

CONCLUSIONS

The infusion of donor bone marrow reduces the rate of acute rejection in heart recipients. Donor bone marrow may play an important role in strategies aiming to enhance the graft acceptance.

Effects of donor bone marrow infusion in clinical lung transplantation

BACKGROUND

We have demonstrated that donor cell chimerism is associated with a lower incidence of obliterative bronchiolitis (OB) in lung recipients, and that donor chimerism is augmented by the infusion of donor bone marrow (BM). We herein report the intermediate results of a trial combining the infusion of donor BM and lung transplantation.

METHODS

Clinical and in vitro data of 26 lung recipients receiving concurrent infusion of donor bone marrow (3.0 to 6.0 x 10(8) cells/kg) were compared with those of 13 patients receiving lung transplant alone.

RESULTS

Patient survival and freedom from acute rejection were similar between groups. Of the patients whose graft survived greater than 4 months, 5% (1 of 22) of BM and 33% (4 of 12) of control patients, developed histologic evidence of OB (p = 0.04). A higher proportion (but not statistically significant) of BM recipients (7 of 10, 70%) exhibited donor-specific hyporeactivity by mixed lymphocyte reaction assays as compared with the controls (2 of 7, 28%).

CONCLUSIONS

Infusion of donor BM at the time of lung transplantation is safe, and is associated with recipients' immune modulation and a lower rate of obliterative bronchiolitis.

Measurement of hemostatic indexes in conjunction with transcranial doppler sonography in patients with ventricular assist devices

BACKGROUND AND PURPOSE

Clinical thromboembolism (TE) remains an impediment to the chronic application of ventricular assist devices (VADs). Microembolic signals (MES) have been detected by transcranial Doppler ultrasound (TCD) in patients with VADs, although their origin and relation to TE remain undefined. We have investigated the hypothesis that hemostatic alterations are related to MES and that MES are associated with TE in a group of 27 VAD patients.

METHODS

Indexes of coagulation, fibrinolysis, and cellular activation and aggregation were measured before and during the VAD implantation period in conjunction with TCD. Groups were defined on the basis of presence of MES, degree of MES showering, and incidence of TE.

RESULTS

MES were observed in 67 (58%) of 115 of individual postoperative TCD measurements and in 21 (78%) of 27 patients. Of patients with TE, 10 (83%) of 12 had detectable MES compared with 11 (73%) of 15 patients without TE (P=0.66). MES were significantly associated with elevated thrombin generation during the implantation period, as reflected by plasma prothrombin fragment F1.2. Elevations in indexes of coagulation, platelet activation, and fibrinolysis relative to normal control subjects were found for patients with VADs with and without detected MES.

CONCLUSIONS

Although no significant relation between MES and TE in VAD patients was found, the data support the hypothesis that MES are related to increased hemostatic activity in this patient group despite aggressive anticoagulant therapy.

Native heart complications after heterotopic heart transplantation: insight into the potential risk of left ventricular assist device

BACKGROUND

In heterotopic heart transplantation, the donor heart is connected parallel to the recipient's diseased heart. Recipients continue to have risks, such as arrhythmia, thromboembolism, valvular heart disease, and ischemic heart disease which can develop in the native heart. It may serve as a clinical model to study long-term pathophysiologic processes in the native heart of patients with a left ventricular assist device.

METHOD

We analyzed the prevalence of long-term complications related to the native heart in the heterotopic heart transplant and attempted to gain insight into the potential risk to a native heart after receiving a left ventricular assist device.

RESULTS

Between December 1984 and December 1994, 16 patients (13 men, 3 women, ranging in age from 37 to 60 years) underwent heterotopic heart transplant at the University of Pittsburgh. The 1- and 5-year survival rate after the transplant was 81% and 44%, respectively. Actuarial freedom from complications related to the native heart after 1 year and 4 years was ventricular arrhythmia: 85%, 75%; ischemic disease: 85%, 64%; valvular disease: 100%, 88%; and thromboembolism: 85%, 58%. Of these complications, thromboembolism was not considered in determining actuarial freedom from complications because thromboembolism should be regarded as a device-related complication rather than as a native-heart-related complication for left ventricular assist device recipients. Consequently, actuarial freedom from all complications excluding thromboembolism was 70% after 1 year and 50% after 4 years. In addition, the hazard function curve remains constant up to 80 months after the operation without significant differences among the yearly ratios.

CONCLUSIONS

This analysis suggests that cautious observation of the native heart's long-term performance is necessary for the left ventricular assist device recipient.

Evaluation of the potential role of color-coded tissue Doppler echocardiography in the detection of allograft rejection in heart transplant recipients

BACKGROUND

Color-coded tissue Doppler (TD) echocardiography can noninvasively quantify alterations in left ventricular (LV) systolic and diastolic function. The objective of this study was to test the hypothesis that TD may play a role in the detection of LV dysfunction associated with allograft rejection in heart transplant recipients.

METHODS AND RESULTS

Seventy-eight consecutive transplant recipients underwent 89 TD studies of posterior wall myocardial velocity gradient and mitral annular velocity within 1 hour of endomyocardial biopsy. Color TD echocardiographic images were digitized for semiautomated computer analysis. Histologic analysis revealed no significant rejection in 75 biopsies and significant rejection in 14. TD posterior wall peak systolic and diastolic velocity gradients were reduced significantly with rejection: 3.9 +/- 2.0 s(-1) versus 2.6 +/- 0.9 s(-1) and 5.4 +/- 2. 4 s(-1) versus 3.5 +/- 1.6 s(-1), respectively (P <.05 vs the nonrejecting group). Peak systolic and diastolic mitral annular velocities by TD were also reduced with rejection: 63 +/- 14 mm/s versus 49 +/- 12.4 mm/s and 90 +/- 23 mm/s versus 60 +/- 21 mm/s, respectively (P <.001 vs the nonrejecting group). A TD peak-to-peak mitral annular velocity >135 mm/s had 93% sensitivity, 71% specificity, and 98% negative predictive value for detecting rejection. Although TD was unable to discriminate between rejection and other causes of low velocity values, high TD velocity values were supportive of excluding rejection.

CONCLUSIONS

These data suggest that color-coded TD may play a potential role as a screening test to exclude rejection in heart transplant recipients. Although this method has the potential to decrease the number of biopsies, further testing in a larger series of transplant recipients with rejection is warranted.

Rotary blood pump flow spontaneously increases during exercise under constant pump speed: results of a chronic study

Many types of rotary blood pumps and pump control methods have recently been developed with the goal of clinical use. From experiments, we know that pump flow spontaneously increases during exercise without changing pump control parameters. The purpose of this study was to determine the hemodynamics associated with the long-term observation of calves implanted with centrifugal blood pumps (EVAHEART, Sun Medical Technology Research Corporation, Nagano, Japan). Two healthy female Jersey calves were implanted with devices in the left thoracic cavity. A total of 22 treadmill exercise tests were performed after the 50th postoperative day. During exercise, the following parameters were compared with conditions at rest: heart rate, blood pressure, central venous oxygen saturation (SvO2), pump speed, and pump flow. The pump flow in a cardiac cycle was analyzed by separating the systole and diastole. Compared to the base data, statistically significant differences were found in the following interrelated parameters: the heart rate (66.8 +/- 5.2 vs. 106 +/- 9.7 bpm), mean pump flow (4.8 +/- 0.2 vs. 7.0 +/- 0.3 L/min), and volume of pump flow in diastole (26.0 +/- 1.8 vs. 13.5 +/- 2.5 ml). During exercise, the volume of pump flow in systole was 3 times larger than that measured in diastole. Blood pressure, SvO2, and pump speed did not change significantly from rest to exercise. These results suggested that the mean pump flow depends on the systolic pump flow. Therefore, the increase in the mean pump flow during exercise under constant pump speed was caused by an increase in the heart rate.

Development of the Nimbus/University of Pittsburgh innovative ventricular assist system

BACKGROUND

Nimbus Inc, and the University of Pittsburgh's McGowan Center for Artificial Organ Development have been collaborators on rotary blood pump technology initiatives since 1992. Currently, a major focus is an innovative ventricular assist system (IVAS) that features an implantable, electrically powered axial flow blood pump. In addition to the blood pump, a major development item is the electronic controller and the control algorithm for modulating pump speed in response to varying physical demand.

METHODS

Methods used in developing the IVAS include computational fluid dynamic modeling of the pump's interior flow field, flow visualization of the flow field using laser-based imaging, computer simulation of blood pump-physiological interactions, vibroaccoustic monitoring, and an extensive in vivo test program.

RESULTS

Results to date, which are presented below, include successful in vivo tests of blood pumps with blood-immersed bearings, and feasibility demonstration of vibroacoustic monitoring in this application.

CONCLUSIONS

This unique blend of industrial experience and technologies with the University-based Research and Development Center has greatly enhanced the progress made on this IVAS project.

Early post-transplant medical compliance and mental health predict physical morbidity and mortality one to three years after heart transplantation

BACKGROUND

Poor medical compliance has been held responsible for a large proportion of deaths occurring subsequent to initial postoperative recovery. However, beyond clinical reports, there has been little empirical examination of this issue, or of the extent to which major psychiatric disorder and failure to adjust to the transplant predict long-term physical morbidity and mortality. We prospectively examined whether a full range of compliance behaviors and psychiatric outcomes during the first year post-transplant predicted subsequent mortality and physical morbidity through 3 years post-transplant.

METHODS

A total of 145 heart recipients who had received detailed compliance and mental health assessments during the first year post-transplant were followed up at 3 years post-transplant. Interview data and corroborative information from family members were used to determine compliance in multiple domains, psychiatric diagnoses, and psychiatric symptomatology during the first year post-surgery. Medical record reviews were performed to abstract data on acute graft rejection episodes, incident cardiac allograft disease (CAD) and mortality from 1 to 3 years post-transplant.

RESULTS

After controlling for known transplant-related predictors of outcome, multivariate analyses yielded the following significant (p < 0.05) results: (a) risk of acute graft rejection was 4.17 times greater among recipients who were not compliant with medications; (b) risk of incident CAD was elevated by persistent depression (Odds Ratio, OR = 4.67), persistent anger-hostility (OR = 8.00), medication noncompliance (OR = 6.91), and obesity (OR = 9.92); and (c) risk of mortality was increased if recipients met criteria for Post-Traumatic Stress Disorder related to the transplant (OR = 13.74).

CONCLUSIONS

The findings, plus data we have previously reported that showed which patients are most likely to have compliance and psychiatric problems early post-transplant, suggest that interventions focused on maximizing patients' psychosocial status in these areas may further improve long-term physical health outcomes in this population.

PTSD in heart transplant recipients and their primary family caregivers

Posttraumatic stress disorder associated with transplantation (PTSD-T) is a complication for some heart transplant recipients. By using a structured, standardized interview and DSM-III-R criteria, the authors examined whether recipients (n = 158) and their family caregivers (n = 142) showed similar PTSD-T rates and clinical characteristics during the first year posttransplant. Among the recipients, 10.5% met full criteria for the disorder and an additional 5% were probable cases. Among the caregivers, 7.7% met full criteria and an additional 11.0% were probable cases. Severity and duration of disorder were similar across the groups. Being female, having a history of psychiatric illness, and having lower friend support were increased risks for PTSD-T.

Chronic animal health assessment during axial ventricular assistance: importance of hemorheologic parameters

Chronic testing of the Nimbus/UOP Axial Flow Pump was performed on 22 calves for periods of implantation ranging from 27 to 226 days (average, 74 days). The following parameters were measured: plasma free hemoglobin, blood and plasma viscosity, erythrocyte deformability and mechanical fragility, oxygen delivery index (ODI), blood cell counts, hematocrit, hemoglobin, blood urea nitrogen, creatinine, bilirubin, total protein, fibrinogen, and plasma osmolality. Most of the above parameters were stable during the full course of support. Compared with baseline, statistically significant differences during the entire period of implantation were only found in: hematocrit (p<0.001), hemoglobin (p<0.005), red blood cell (RBC) count (p<0.001), and whole blood viscosity (p<0.01). Plasma viscosity and ODI were mostly stable during the period of implantation. In some animals, an acute increase in fibrinogen concentration, plasma and blood viscosity, and a decrease in ODI were found to be early signs of the onset of infection. A small (10%) decrease in deformability of RBCs was found during the first 2 weeks after implantation. This alteration in RBC deformability was highly correlated (r = 0.793) with changes in total plasma protein concentration that fell more than 15% (p<0.001) during the same period. Mechanical fragility of RBCs was found to be slightly increased after implantation. Plasma free hemoglobin remained close to baseline level (p>0.2). After the first 2 weeks of the postoperative period, pump performing parameters for all animals were consistent and stable. In general, the Nimbus/UOP Axial Flow Pump demonstrated basic reliability and biocompatibility and did not produce significant alterations in the mechanical properties of blood or animal health status. The pump provided adequate hemodynamics and was well tolerated by the experimental animal for periods as long as 7.5 months. Monitoring rheologic parameters of blood is very helpful for evaluation of health during heart-assist device application.

Quality of life outcomes in left ventricular assist system inpatients and outpatients

This study empirically evaluates the quality of life (QOL) effects associated with hospital discharge among heart transplant candidates whose lives are maintained by left ventricular support systems (LVAS). Thirty-five LVAS inpatients (18 Novacor, 17 Thoratec) received structured QOL assessments approximately 1 month after device implant. Ten of the patients (8 Novacor, 2 Thoratec) were subsequently discharged to either home or a home-like outpatient facility where their QOL was reassessed. The QOL of LVAS patients, before and after discharge, was compared with that of demographically similar nonhospitalized heart transplant candidates (n = 55) and recipients (n = 97). Their caregivers' QOL was also assessed. The QOL of LVAS outpatients showed statistically significant (p<0.05) advantages over remaining LVAS inpatients and nonhospitalized heart candidates. Advantages appeared in physical, emotional, and social functioning domains. The QOL of LVAS outpatients also improved (p<0.05) over their own QOL before discharge, with the greatest change in physical functional and emotional status. The QOL of LVAS outpatients most closely resembled QOL in the transplant recipients. Family caregivers to LVAS outpatients reported some increases in caregiving burden after patient discharge, but their overall well being was not adversely affected. These data provide an empiric basis for the provision of outpatient programs as appropriate care for eligible LVAS patients.

Biomedical engineering management of Novacor left ventricular assist system (LVAS) patients

As the number of cardiac transplant centres increases, there is an associated decrease in the availability of donor organs per centre. Subsequently, hospitals are utilizing cardiac assist systems (total artificial heart and ventricular assist devices) as a bridge to cardiac transplantation. Because of the engineering complexities related to the clinical implantation and follow up of these devices, a successful centre should have a well co-ordinated biomedical engineering programme. These engineers are responsible for the calibration, monitoring, and continued operation of these units. This paper is intended to serve as a guide to any centre interested in utilizing total artificial heart and ventricular assist systems, in particular the Novacor left ventricular assist system, and focuses on the management and function of the biomedical engineering component of our cardiac assist programme.

The CardioWest total artificial heart bridge to transplantation: 1993 to 1996 national trial

BACKGROUND

We performed a controlled study of a total artificial heart in bridge to transplantation. We hypothesized that the CardioWest total artificial heart used in a selected population of decompensating cardiac transplantation candidates would result in improved survival compared with matched controls.

METHODS

The CardioWest trial started in 1993 in six United States institutions under an investigational device exemption from the Food and Drug Administration. Four centers contributed 27 implant and 18 matched retrospective control patients.

RESULTS

Of the implant patients, 25 (93%) received a transplant, 24 (89% of the total, 96% of those transplanted) were discharged and are currently surviving. In the control group, 10 patients died awaiting transplantation, 8 received a transplant, and 7 were discharged with 6 surviving (p = 0.00001). All adverse events were documented with respect to time. Thirteen serious adverse events occurred, 11 of which occurred in the 2 patients that died during implant.

CONCLUSIONS

In a selected group of patients with endstage heart disease, use of the CardioWest total artificial heart is lifesaving. When compared with the series of matched retrospective controls, a significant improvement in survival was found in the CardioWest implant group.

Traumatic aortic rupture: diagnosis and management

BACKGROUND

Traumatic aortic rupture is a relatively uncommon lesion that presents the cardiothoracic surgeon with unique challenges in diagnosis and management. To address controversial aspects of this disease, we reviewed our experience.

METHODS

The study was performed by retrospective chart review.

RESULTS

Forty-two patients with traumatic thoracic aortic ruptures were managed between January 1988 and June 1997. Nine arrived without vital signs and died in the emergency department. Admission chest radiographs were normal in 3 patients (12%) and caused significant delays in diagnosis. Four of 30 patients admitted with vital signs had rupture before thoracotomy and died. Twenty-six underwent aortic repair. In 1 patient repair was performed with simple aortic cross-clamping, whereas a second was managed with a Gott shunt. The remaining 24 patients had repair with partial left heart bypass. In 1 patient hypothermic circulatory arrest was required. Two patients (7.7%) died. There were no cases of new postoperative paraplegia in the bypass group. There was no morbidity directly attributable to the administration of heparin for cardiopulmonary bypass.

CONCLUSIONS

In a discrete group of patients with traumatic rupture of the aorta, the rupture will become complete during the first few hours of hospital admission; aggressive medical treatment with beta-blockade and vasodilators in the interval before the operation is an essential aspect of management. Active distal circulatory support with partial left-heart bypass provides the optimal means of preventing spinal cord ischemia during repair of acute traumatic aortic rupture.

Progress on development of the Nimbus-University of Pittsburgh axial flow left ventricular assist system

Nimbus Inc. (Rancho Cordova, CA) and the University of Pittsburgh have completed the second year of development of a totally implanted axial flow blood pump under the National Institutes of Health Innovative Ventricular Assist System Program. The focus this year has been on completing pump hydraulic development and addressing the development of the other key system components. Having demonstrated satisfactory pump hydraulic and biocompatibility performance, pump development has focused on design features that improve pump manufacturability. A controller featuring full redundancy has been designed and is in the breadboard test phase. Initial printed circuit layout of this circuit has shown it to be appropriately sized at 5 x 6 cm to be compatible with implantation. A completely implantable system requires the use of a transcutaneous energy transformer system (TETS) and a diagnostic telemetry system. The TETS power circuitry has been redesigned incorporating an improved, more reliable operating topography. A telemetry circuit is undergoing characterization testing. Closed loop speed control algorithms are being tested in vitro and in vivo with good success. Eleven in vivo tests were conducted with durations from 1 to 195 days. Endurance pumps have passed the 6 month interval with minimal bearing wear. All aspects of the program continue to function under formal quality assurance.

Predicting short-term outcome in severely ill heart failure patients: implications regarding listing for urgent cardiac transplantation and patient selection for temporary ventricular assist device support

BACKGROUND

The purpose of this study was to determine which patients on a cardiac transplantation list required a ventricular assist device.

METHODS AND RESULTS

In a preliminary study, 26 patients with decompensated severe New York Heart Association class IV chronic heart failure were studied. Blood levels for sodium, hemoglobin, cytokines, neurohormones, and hemodynamics were obtained. During short-term follow-up of 40 days, 12 patients had undergone emergent implantation of a ventricular assist device (range 1-27 days, mean 5 days), 4 died (range 14-38 days, mean 26 days), and 5 were alive and receiving only medical therapy while waiting for a transplantation. In addition, five patients had undergone transplantation (range 5-29 days, mean 18 days, excluded from further analysis). Survival curves were constructed by comparing the incidence of death and the implantation of an emergent ventricular assist device in patients with values of a variable above or below the mean value (or median for nonnormally distributed data). There was a significantly greater incidence of death or need for a ventricular assist device in patients with higher levels of tumor necrosis factor-alpha (P = .008), lower levels of serum sodium and hemoglobin (P = .02 and P = .03, respectively), higher heart rates (P = .03), and higher plasma norepinephrine levels (P = .01). The Cox proportional hazards model demonstrated that only serum sodium (P = .03) independently predicted those patients who died or who required emergent left ventricular assist device.

CONCLUSION

Numerous variables, particularly serum sodium, need to be considered when evaluating which patients on the transplant list require early assist device implantation or urgent transplantation. These preliminary observations merit confirmation in a larger patient population.

Patient survival with renal replacement therapy in heart transplantation patients

Long-term survivors of cardiac transplantation are at risk for nephrotoxicity caused by many years of immunosuppressive therapy with cyclosporine or tacrolimus. We report on 12 patients who received heart transplants at the University of Pittsburgh, with subsequent development of end-stage renal disease (ESRD), who received renal replacement therapy at the university affiliated dialysis program. Patients were grouped by initial dialysis modality as intent to treat. Four patients were on chronic hemodialysis (HD) and eight on peritoneal dialysis (PD). Six patients died, two on HD and four on PD. There were 451 deaths per 1000 patient years for patients on PD compared with 273 deaths per 1000 patients years for patients on HD (p < 0.0001), both significantly higher than the United States Renal Data System rate of 178 per 1000 patient years for patients with ESRD who were of similar age and race, p < 0.0001. The survival rate for patients on PD seemed to be worse, but that may be because unstable patients with failing heart transplants were directed toward PD. Efforts should be made to minimize nephrotoxicity after cardiac transplantation.

Novel ventricular apical cannula: in vitro evaluation using transparent, compliant ventricular casts

The geometric configuration of the cannula connection to the left ventricular (LV) apex was studied with respect to several characteristics defining functionality and compatibility. The authors had previously determined, through in vivo studies in sheep, that the design of the cannula used with a dynamic blood pump for LV circulatory support can significantly affect the hemodynamics by improving both the bypass flow rate and the fluid dynamics within the ventricle. The tip of the cannula can aid in preventing wall to wall ventricular collapse, as well as septal shift, due to reduced LV pressure. Proper surgical placement of the cannula with respect to the endocardial surface of the LV can also be simplified by the tip geometry. To investigate the anatomic interaction and fluid dynamics of apical cannulation, transparent compliant casts of bovine LVs were fabricated for in vitro flow visualization. Two different heart geometries were cast, end systolic and end diastolic. The latter was fitted with a pericardial mitral valve and pressurized in a pulsatile fashion to simulate the wall movement of a beating heart. The internal flow and anatomy were visualized with fluorescent particle tracking velocimetry. These studies were performed with conventional cannula tips, as well as a novel, trumpet mouth cannula. The visualization clearly shows the dramatic differences in flow between the geometries tested, and strongly advocates a trumpet mouth design. This novel tip demonstrated excellent placement, beneficial stenting, and improved blood flow by reducing apical stasis and recirculation. Ongoing evaluation of these and future geometries include the application of in vitro endoscopy, quantitative velocimetry, and extension to dilated human ventricles.

An implantable centrifugal blood pump with a recirculating purge system (Cool-Seal system)

A compact centrifugal blood pump has been developed as an implantable left ventricular assist system. The impeller diameter is 40 mm, and pump dimensions are 55 x 64 mm. This first prototype, fabricated from titanium alloy, resulted in a pump weight of 400 g including a brushless DC motor. The weight of a second prototype pump was reduced to 280 g. The entire blood contacting surface is coated with diamond like carbon (DLC) to improve blood compatibility. Flow rates of over 7 L/min against 100 mm Hg pressure at 2,500 rpm with 9 W total power consumption have been measured. A newly designed mechanical seal with a recirculating purge system (Cool-Seal) is used for the shaft seal. In this seal system, the seal temperature is kept under 40 degrees C to prevent heat denaturation of blood proteins. Purge fluid also cools the pump motor coil and journal bearing. Purge fluid is continuously purified and sterilized by an ultrafiltration unit which is incorporated in the paracorporeal drive console. In vitro experiments with bovine blood demonstrated an acceptably low hemolysis rate (normalized index of hemolysis = 0.005 +/- 0.002 g/100 L). In vivo experiments are currently ongoing using calves. Via left thoracotomy, left ventricular (LV) apex descending aorta bypass was performed utilizing an expanded polytetrafluoroethylene (ePTFE) vascular graft with the pump placed in the left thoracic cavity. In 2 in vivo experiments, the pump flow rate was maintained at 5-9 L/min, and pump power consumption remained stable at 9-10 W. All plasma free Hb levels were measured at less than 15 mg/dl. The seal system has demonstrated good seal capability with negligible purge fluid consumption (<0.5 ml/day). In both calves, the pumps demonstrated trouble free continuous function over 6 month (200 days and 222 days).

Fine trabecularized carbon: ideal material and texture for percutaneous device system of permanent left ventricular assist device

The development of a percutaneous artificial internal organ system requires a reliable biocompatible connection between the external environment and the inside of the human body. Such is necessary for the success of a permanent left ventricular assist device. However, the search for a satisfactory interface at the epidermal level has proven to be difficult. Carbon has been proposed for this application, but its texture does not typically promote ingrowth from surrounding tissue. We have therefore employed a new processing method to produce a fine trabecularized carbon implant. The method for preparing the implant involves infiltrating low temperature pyrolytic carbon into the surface of a carbon core which is wrapped with carbon fabric. This results in a tightly woven porous structure of carbon (carbon fiber diameter: 35-50 microm, maximal pore size >200 microm) with gradually increasing porosity from 15-75%. We implanted test samples percutaneously in a calf for in vivo histological evaluation. Thirty days after implantation epidermal downgrowth was minimal. Microscopic analysis revealed that a thin fibrous capsule surrounded the implant, and mature connective tissue with accompanying blood vessels filled the pores of the fine trabecularized carbon layer. From these results we suggest that fine trabecularized carbon is ideally suited for a percutaneous device system in a permanent left ventricular assist device.

Effect of pressure-flow relationship of centrifugal pump on in vivo hemodynamics: a consideration for design

We have been developing centrifugal pumps for an implantable left ventricular assist device. We manufactured 2 prototype centrifugal pumps (PI, PII). These two have similar designs except for the PII having a volute casing and a large output port. To determine the differences in the hydraulic characteristics between the PI and PII, we carried out in vitro and in vivo experiments. In vitro study showed that the PII had a shallower H-Q curve than that of the PI, and the PII required a pump speed faster than the PI for the same flow rate and pressure head. On the other hand, in vivo study showed that the PII demonstrated a flow pulsatility greater than that of the PI at 1,900 rpm and 8 L/min although no significant change was observed at low pump speeds (< or = 1,500 rpm). This greater pulsatility consisted of a large discharge according to the small differential pressure during the systolic phase and a small discharge according to the large differential pressure during the diastolic phase. In contrast, the PI, having the steeper H-Q curve, showed a small discharge in the systolic phase and a large discharge in the diastolic phase. These results showed that pulsatility synchronized with the native heart beating depended on the slope of the H-Q curve. As a result, the slope of the H-Q curve is important to determine the component of pulsatility synchronized with native cardiac output. Regarding the slope of the H-Q curve, a pump having a volute casing and a large outlet port demonstrates a shallow slope in the H-Q curve. In conclusion, we suggest that a centrifugal pump for use in left ventricular aortic bypass should be designed considering the effect on the native heart pulsatility.

Monocyte tissue factor expression and ongoing complement generation in ventricular assist device patients

BACKGROUND

Ongoing complement activation in patients with a ventricular assist device may contribute to observed hemostatic abnormalities and cellular aggregation by mediating leukocyte and platelet activation, formation of leukocyte-platelet conjugates, and the tissue factor pathway of coagulation.

METHODS

Blood from 30 patients was collected before ventricular assist device implantation and during the implantation period. Plasma levels of thrombin-antithrombin III complexes, C3a, and SC5b-9 were measured by commercial enzyme-linked immunosorbent assay. Flow cytometry was used to measure circulating monocyte tissue factor expression and circulating monocyteplatelet and granulocyte-platelet conjugates.

RESULTS

Thrombin-antithrombin III complex level and monocyte tissue factor expression peaked in the early postoperative period, with maxima occurring on postoperative days 5 and 3, respectively. Levels of C3a and SC5b-9 remained dramatically elevated over normal values for the duration of the study (6 and 5 times upper normal, respectively). Levels of monocyte-platelet conjugates were normal before implantation, decreased during the first 4 postoperative days, and then increased and remained elevated. Levels of granulocyte-platelet conjugates were elevated over the normal range before implantation and remained elevated from postoperative days 3 to 21. A positive correlation was found between levels of SC5b-9 and granulocyte-platelet conjugates (Spearman R=0.66; p < 0.001), and between levels of C3a and thrombin-antithrombin III complex (Spearman R=0.13; p=0.021).

CONCLUSIONS

The data suggest a model in which complement mediates formation of leukocyte-platelet aggregates and may indirectly contribute to thrombin generation through monocyte tissue factor expression.