Immunobiology of left ventricular assist devices

Cellular and Molecular Mechanisms Activated by a Left Ventricular Assist Device

Left ventricular assist devices (LVADs) represent the final treatment for patients with end-stage heart failure (HF) not eligible for transplantation. Although LVAD design has been further improved in the last decade, their use is associated with different complications. Specifically, inflammation, fibrosis, bleeding events, right ventricular failure, and aortic valve regurgitation may occur. In addition, reverse remodeling is associated with substantial cellular and molecular changes of the failing myocardium during LVAD support with positive effects on patients' health. All these processes also lead to the identification of biomarkers identifying LVAD patients as having an augmented risk of developing associated adverse events, thus highlighting the possibility of identifying new therapeutic targets. Additionally, it has been reported that LVAD complications could cause or exacerbate a state of malnutrition, suggesting that, with an adjustment in nutrition, the general health of these patients could be improved.

Antibody Response to SARS-CoV-2 Vaccination in Heart Failure Patients: Retrospective Single-Center Cohort Study

We sought to investigate the impact of heart failure on anti-spike antibody positivity following SARS-CoV-2 vaccination. Our study included 103 heart failure (HF) patients, including those with and without left ventricular assist devices (LVAD) selected from our institutional transplant waiting list as well as 104 non-heart failure (NHF) patients who underwent open heart surgery at our institution from 2021 to 2022. All the patients received either heterologous or homologous doses of BNT162b2 and CoronaVac. The median age of the HF group was 56.0 (interquartile range (IQR): 48.0-62.5) and the NHF group was 63.0 (IQR: 56.0-70.2) years, and the majority were males in both groups (n = 78; 75.7% and n = 80; 76.9%, respectively). The majority of the patients in both the HF and NHF groups received heterologous vaccinations (n = 43; 41.7% and n = 52; 50.3%, respectively; p = 0.002). There was no difference in the anti-spike antibody positivity between the patients with and without heart failure (p = 0.725). Vaccination with BNT162b2 led to significantly higher antibody levels compared to CoronaVac alone (OR: 11.0; 95% CI: 3.8-31.5). With each passing day after the last vaccine dose, there was a significant decrease in anti-spike antibody positivity, with an OR of 0.9 (95% CI: 0.9-0.9). Furthermore, hyperlipidemia was associated with increased antibody positivity (p = 0.004).

HLA Sensitization in Patients Bridged to Lung Transplantation With Extracorporeal Membrane Oxygenation

Lung transplantation is a definitive therapy for many end-stage lung pathologies. Extracorporeal membrane oxygenation (ECMO) is increasingly being used as a bridge to lung transplantation (BTT). HLA sensitization is a major barrier to lung transplantation. The development of HLA sensitization while undergoing ECMO support as a BTT has recently been reported in a 2-patient series.

Methods

We performed a retrospective analysis of patients undergoing ECMO as a BTT at a single large academic medical center from January 2016 to April 2022. The study was approved by the institutional review board. We selected patients who had undergone ECMO support for at least 7 d with either negative HLA before cannulation or initial negative HLA on ECMO (3 patients).

Results

We identified 27 patients bridged to lung transplantation with available HLA data. Of this group, 8 patients (29.6%) developed significant HLA sensitization (>10%). We did not identify any factors predisposing to sensitization, including infection episodes or blood product transfusion. Sensitized patients demonstrated a trend toward an increased primary graft dysfunction rate, a need for posttransplant ECMO support, and a decreased 1-y survival; however, these did not meet statistical significance.

Conclusions

Our study is the largest series today describing the association between HLA sensitization and ECMO therapy. We suggest that interaction between the immune system and ECMO circuit contributes to allosensitization pretransplant, similar to that occurring with ventricular assist device. Further work is needed to better characterize the incidence of HLA sensitization in a multicenter cohort and to identify potentially modifiable factors associated with HLA sensitization.

Detection and management of HLA sensitization in candidates for adult heart transplantation

Heart transplantation (HT) remains the preferred therapy for patients with advanced heart failure. However, for sensitized HT candidates who have antibodies to human leukocyte antigens , finding a suitable donor can be challenging and can lead to adverse waitlist outcomes. In recent years, the number of sensitized patients awaiting HT has increased likely due to the use of durable and mechanical circulatory support as well as increasing number of candidates with underlying congenital heart disease. This State-of-the-Art review discusses the assessment of human leukocyte antigens antibodies, potential desensitization strategies including mechanisms of action and specific protocols, the approach to a potential donor including the use of complement-dependent cytotoxicity, flow cytometry, and virtual crossmatches, and peritransplant induction management.

Current Desensitization Strategies in Heart Transplantation

Heart transplant candidates sensitized to HLA antigens wait longer for transplant, are at increased risk of dying while waiting, and may not be listed at all. The increasing prevalence of HLA sensitization and limitations of current desensitization strategies underscore the urgent need for a more effective approach. In addition to pregnancy, prior transplant, and transfusions, patients with end-stage heart failure are burdened with unique factors placing them at risk for HLA sensitization. These include homograft material used for congenital heart disease repair and left ventricular assist devices (LVADs). Moreover, these risks are often stacked, forming a seemingly insurmountable barrier in some cases. While desensitization protocols are typically implemented uniformly, irrespective of the mode of sensitization, the heterogeneity in success and post-transplant outcomes argues for a more tailored approach. Achieving this will require progress in our understanding of the immunobiology underlying the innate and adaptive immune response to these varied allosensitizing exposures. Further attention to B cell activation, memory, and plasma cell differentiation is required to establish methods that durably abrogate the anti-HLA antibody response before and after transplant. The contribution of non-HLA antibodies to the net state of sensitization and the potential implications for graft longevity also remain to be comprehensively defined. The aim of this review is to first bring forth select issues unique to the sensitized heart transplant candidate. The current literature on desensitization in heart transplantation will then be summarized providing context within the immune response. Building on this, newer approaches with therapeutic potential will be discussed emphasizing the importance of not only addressing the short-term pathogenic consequences of circulating HLA antibodies, but also the need to modulate alloimmune memory.

IgA Vasculitis With Henoch-Schönlein Purpura as an Immune Complication Associated With Left Ventricle Assist Device Insertion

The implantation of left ventricular assist devices (LVADs) in patients with end-stage heart failure can be associated with some forms of immune dysregulation and systemic inflammatory response. These abnormalities may be related to impaired T-lymphocyte-dependent immunity and B-lymphocyte hyper-reactivity and may lead to the development of autoimmune processes and the occurrence of severe infections. We present here the first observation of a peculiar immune complication associated with the implantation of an LVAD, characterized by an IgA vasculitis clinically manifested as Henoch-Schönlein purpura. The vasculitis was biologically associated with a significant increase of the plasma levels of C-X-C motif chemokine ligand (CXCL)13, a CXC motif chemokine produced by follicular dendritic cells, which targets CXCR5, a receptor primarily expressed by B lymphocytes, to promote their chemotaxis and expansion. Spontaneous resolution of the vasculitis occurred over time, concomitantly to a decrease of CXCL13 expression. These findings suggest that CXCL13 might be an interesting biomarker to detect auto-antigen sampling and the risk of secondary immune complications following LVAD implantation.

Cytomegalovirus reactivation in left ventricular assist device patients: case series and literature review

Background 

Cytomegalovirus (CMV) reactivation after placing left ventricular assist device (LVAD) is not a well-known entity with few cases reported in the literature. Here, we are presenting three cases of CMV reactivation after placing LVAD. A literature review of all reported cases in the literature was done.

Case summary 

Three cases of advanced heart failure with reduced ejection fraction (Stage D9) had placed (LVAD) at the American University of Beirut Medical Center, a tertiary care centre in Lebanon. Within the first 2 weeks after LVAD implantation, the three patients spiked a high-grade fever for which sepsis workup was done, and antibiotics were initiated. Despite the escalating antibiotic regimens, the three patients had a persistent high-grade fever. The negative cultures and the continuous fever prompted an investigation for other causes of fever. Therefore, CMV polymerase chain reaction in blood was performed and revealed high titres. Patients received a full course of treatment with ganciclovir. The fever and the CMV titres declined after completing the antiviral therapy with better clinical outcomes. This raises the concern of CMV reactivation in LVAD patients.

Discussion 

This case series and literature review highlight the epidemiology, incidence, and management of CMV reactivation among LVAD patients. Awareness about this clinical entity should be raised, especially with the increase of LVAD surgeries.

Intracranial Mycotic Aneurysm in a Left Ventricular Assist Device Patient: A Complication to Avoid

In the current era of the increasing use of left ventricular assist devices (LVADs) as a bridge to transplant or destination therapy, early diagnosis and therapy of complications are imperative to provide a better quality of life and improve outcomes. This case illustrates how superficial infections can lead to drastic complications in the setting of LVADs. The lack of signs and symptoms of systemic inflammatory response could be explained by cellular immunity impairment in patients on LVAD support. The formation of aneurysms is enhanced in the LVAD population due to altered hemodynamic physiology. It is possible that the combination of impaired cellular immunity and altered hemodynamics of the present-day continuous flow LVADS increases the risk of mycotic aneurysm formation and rupture in patients infected with less virulent organisms.

Seroreversion of positive anti-hepatitis C virus antibodies in left ventricular assist device recipients: Now you see them, now you don't

The clinical significance of positive anti-hepatitis C virus (anti-HCV) antibody tests in recipients of left ventricular assist devices remains unclear. In light of emerging evidence suggesting the possibility of persistent low-level HCV infection in patients with positive anti-HCV antibody test but negative HCV ribonucleic acid, it is very important to distinguish the truly false positive HCV antibodies, in recipients of continuous flow left ventricular assist devices, from those suggestive of a prior clinically resolved infection or one where a low-level viremia may have persisted. We conducted a retrospective analysis of left ventricular assist device recipients at our institution. While the total incidence of positive HCV antibody with concomitantly negative HCV ribonucleic acid test (19.2%) was in keeping with the incidences reported in prior cross-sectional studies, we longitudinally followed our patients and observed a 100% seroreversion. Seroreversion, which has not been reported in other studies, occurred either during continued left ventricular assist device support (10 out of 26) or after heart transplant (7 out of 26). Hundred percent seroreversion strongly suggested that the anti-HCV antibodies were truly false positive.

Delayed febrile response with bloodstream infections in patients with continuous-flow left ventricular assist devices

Bloodstream infections (BSIs) are common in patients with continuous-flow left ventricular assist devices (CF-LVADs). Whether CF-LVADs modulate the febrile response to BSIs is unknown. We retrospectively compared the febrile response to BSIs in patients with heart failure (HF) with CF-LVADs versus a control population of patients with HF receiving inotropic infusions. BSIs were adjudicated using the Centers for Disease Control and Prevention and the National Healthcare Safety Network criteria. Febrile status (temperature ≥38°C, 100.4 °F), temperature at presentation with BSI, and the highest temperature within 72 hours (Tmax) were collected. We observed 59 BSIs in LVAD patients and 45 BSIs in controls. LVAD patients were more likely to be afebrile and to have a lower temperature at presentation than control (88% vs 58%, p=0.002, and 37°C ±0.7 vs 37.7°C ±1.0, p=0.0009, respectively). By 72 hours, the difference in afebrile status diminished (53% vs 44%, p=0.42), and the Tmax was similar between the LVAD and control groups (37.9°C±0.9 vs 38.2°C±0.8, respectively, p=0.10). In conclusion, at presentation with a BSI, the vast majority of CF-LVAD patients were afebrile, an event which occurred at a higher frequency when compared with patients with advanced HF on chronic inotropes via an indwelling venous catheter. These data alert clinicians to have a very low threshold to obtain blood cultures in CF-LVAD patients even in the absence of fever. Further study is needed to determine whether a delayed or diminished febrile response represents another pathophysiological consequence of CF-LVADs.

Association of pro-inflammatory cytokines and monocyte subtypes in older and younger patients on clinical outcomes after mechanical circulatory support device implantation

Noninvasive immunologic analysis of peripheral blood holds promise for explaining the mechanism of development of adverse clinical outcomes, and may also become a method for patient risk stratification before or after mechanical circulatory support device (MCSD) implantation. Dysregulation of the innate immune system is associated with increased patient age but has yet to be evaluated in the older patient with advanced heart failure undergoing MCSD surgery. Patients pre- and post-MCSD implantation had peripheral blood mononuclear cells (PBMC) and serum isolated. Multiparameter flow cytometry was used to analyze markers of innate cell function, including monocyte subtypes. Multiplex cytokine analysis was performed. MELD-XI and SOFA scores were utilized as surrogate markers of outcomes. Increased levels of pro-inflammatory cytokines including IL-15, TNF-α, and IL-10 were associated with increased MELD-XI and SOFA scores. IL-8, TNF- α, and IL-10 were associated with risk of death after MCSD implantation, even with correction for patient age. Increased frequency of 'classical' monocytes (CD14 + CD16-) were associated with increased MELD-XI and SOFA scores. This suggests that inflammation and innate immune system activation contribute to progression to multiorgan system failure and death after MCSD surgery. Development of noninvasive monitoring of peripheral blood holds promise for biomarker development for candidate selection and patient risk stratification.

Ovine Leukocyte Microparticles Generated by the CentriMag Ventricular Assist Device In Vitro

Ventricular assist devices (VADs) are a life-saving form of mechanical circulatory support in heart failure patients. However, VADs have not yet reached their full potential due to the associated side effects (thrombosis, bleeding, infection) related to the activation and damage of blood cells and proteins caused by mechanical stress and foreign materials. Studies of the effects of VADs on leukocytes are limited, yet leukocyte activation and damage including microparticle generation can influence both thrombosis and infection rates. Therefore, the aim was to develop a multicolor flow cytometry assessment of leukocyte microparticles (LMPs) using ovine blood and the CentriMag VAD as a model for shear stress. Ovine blood was pumped for 6 h in the CentriMag and regular samples analyzed for hemolysis, complete blood counts and LMP by flow cytometry during three different pump operating conditions (low flow, standard, high speed). The high speed condition caused significant increases in plasma-free hemoglobin; decreases in total leukocytes, granulocytes, monocytes, and platelets; increases in CD45⁺ LMPs as well as two novel LMP populations: CD11b^bright /HLA-DR^- and CD11b^dull /HLA-DR⁺ , both of which were CD14^- /CD21^- . CD11b^bright /HLA-DR^- LMPs appeared to respond to an increase in shear magnitude whereas the CD11b^dull /HLA-DR⁺ LMPs significantly increased in all pumping conditions. We propose that these two populations are released from granulocytes and T cells, respectively, but further research is needed to better characterize these two populations.

T cell dysfunction and patient age are associated with poor outcomes after mechanical circulatory support device implantation

Immunologic impairment may contribute to poor outcomes after implantation of mechanical circulatory support device (MCSD), with infection often as a terminal event. The study of immune dysfunction is of special relevance given the growing numbers of older patients with heart disease. The aim of the study was to define which immunologic characteristics are associated with development of adverse clinical outcomes after MCSD implantation. We isolated peripheral blood mononuclear cells (PBMC) from patients pre- and up to 20 days post-MCSD implantation and analyzed them by multiparameter flow cytometry for T cell dysfunction, including terminal differentiation, exhaustion, and senescence. We used MELD-XI and SOFA scores measured at each time point as surrogate markers of clinical outcome. Older patients demonstrated increased frequencies of terminally differentiated T cells as well as NKT cells. Increased frequency of terminally differentiated and immune senescent T cells were associated with worse clinical outcome as measured by MELD-XI and SOFA scores, and with progression to infection and death. In conclusion, our data suggest that T cell dysfunction, independently from age, is associated with poor outcomes after MCSD implantation, providing a potential immunologic mechanism behind patient vulnerability to multiorgan dysfunction and death. This noninvasive approach to PBMC evaluation holds promise for candidate evaluation and patient monitoring.

The effect of ventricular assist device-associated biomaterials on human blood leukocytes

Ventricular assist devices (VADs) are an effective bridging or destination therapy for patients with advanced stage heart failure. These devices remain susceptible to adverse events including infection, bleeding, and thrombus; events linked to the foreign body response. Therefore, the biocompatibility of all biomaterials used is crucial to the success of medical devices. Biomaterials common in VADs-DLC: diamond-like carbon coated stainless steel; Sap: single-crystal sapphire; SiN: silicon nitride; Ti: titanium alloy; and ZTA: zirconia-toughened alumina-were tested for their biocompatibility through incubation with whole human blood for 2 h with mild agitation. Blood was then removed and used for: complete cell counts; leukocyte activation and death, and the production of key inflammatory cytokines. All were compared to time 0 and an un-exposed 2 h sample. Monocyte numbers were lower after exposure to DLC, SiN, and ZTA and monocytes showed evidence of activation with DLC, Sap, and SiN. Neutrophils and lymphocytes were unaffected. This approach allows comprehensive analysis of the potential blood damaging effects of biomaterials. Monocyte activation by DLC, Sap, ZTA, and SiN warrants further investigation linking effects on this cell type to unfavorable inflammatory/thrombogenic responses to VADs and other blood handling devices. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1730-1738, 2018.

Clinical significance of anti-HLA antibodies associated with ventricular assist device use in pediatric patients: A United Network for Organ Sharing database analysis

While VAD use in pediatric patients has previously been associated with anti-HLA antibody production, the clinical significance of these antibodies is unclear. We investigated the clinical impact of anti-HLA antibodies associated with VAD use in a large cohort of pediatric HTx recipients. From 2004 to 2011, pediatric cardiomyopathy patients post-HTx (N=1288) with pre-HTx PRA levels were identified from the United Network for Organ Sharing database. PRA levels were compared between VAD patients and those with no history of MCS. Incidence of rejection and overall survival were compared between VAD and non-MCS groups after stratification by PRA and age. VAD recipients were more likely to produce anti-HLA antibodies than non-MCS patients (25.5% vs 10.5% had PRA>10%, P<.0001). Sensitized VAD patients (PRA>10%) had a higher incidence of rejection within 15 months of HTx compared to sensitized non-MCS patients (57.1% vs 35.9%, P=.02). There was no intergroup difference in 15-month mortality. Among pediatric cardiomyopathy patients supported with a VAD, the presence of anti-HLA antibodies prior to HTx is associated with an increased risk of rejection. The mechanism of the association between VAD-associated antibodies and early rejection is unclear and warrants further investigation.

False positive hepatitis C antibody test results in left ventricular assist device recipients: increased risk with age and transfusions

Left ventricular assist devices (LVADs) have been successfully used in patients with heart failure. However, LVADs may trigger immune activation, leading to higher frequencies of autoantibodies. We describe the clinical, epidemiological, and laboratory characteristics of LVAD recipients with false positive hepatitis C (FPHC) serology among 39 consecutive adult LVAD recipients who bridged to heart transplantation from January 2007 to January 2013 at Montefiore Medical Center. FPHC patients were identified as those with post-LVAD positive hepatitis C ELISA antibody tests and negative confirmatory testing with hepatitis C RNA PCR and/or radioimmunoblot assay. Ten (26%) patients previously seronegative for hepatitis C were found to have FPHC after device placement. Of the 39 patients, 32 had HeartMate II devices. The mean age at LVAD placement was 55 years. FPHC correlated with older age at the time of LVAD implantation and with receipt of packed red blood cell transfusions, but not with gender, fresh frozen plasma transfusions, panel reactive antibodies, globulin fraction, rheumatoid factor, or anticardiolipin antibodies. Clinicians should be aware of this increased risk of FPHC in older LVAD patients and those more heavily transfused in order to avoid unnecessary apprehension and possible delay in transplantation. Further studies should be done to evaluate the possible relationship between transfused blood products and immunomodulation.

Immunological and Fibrotic Mechanisms in Cardiac Allograft Vasculopathy

Cardiac allograft vasculopathy (CAV) has a high prevalence among patients that have undergone heart transplantation. Cardiac allograft vasculopathy is a multifactorial process in which the immune system is the driving force. In this review, the data on the immunological and fibrotic processes that are involved in the development of CAV are summarized. Areas where a lack of knowledge exists and possible additional research can be completed are pinpointed. During the pathogenesis of CAV, cells from the innate and the adaptive immune system cooperate to reject the foreign heart. This inflammatory response results in dysfunction of the endothelium and migration and proliferation of smooth muscle cells (SMCs). Apoptosis and factors secreted by both the endothelium as well as the SMCs lead to fibrosis. The migration of SMCs together with fibrosis provoke concentric intimal thickening of the coronary arteries, which is the main characteristic of CAV.

Early expression of pro- and anti-inflammatory cytokines in left ventricular assist device recipients with multiple organ failure syndrome

To assess whether the combined evaluation of total Sequential Organ Failure Assessment (t-SOFA) score and pro- and anti-inflammatory cytokine profiles early after left ventricular assist device (LVAD) implant discriminates patients at high risk for multiple organ failure syndrome (MOFS) in the first month post-LVAD, we analyzed plasma interleukin (IL)-6, IL-8, IL-10, IL-1ra, IL-1beta, tumor necrosis factor-alpha (TNF-alpha), and urine neopterin levels before (day 0) and at 4 hours, 1, 3, 7, 14, and 30 days after LVAD implant in 23 recipients. Eight patients died of MOFS between days 7 and 30 (nonsurvivors). At preimplant, only blood urea nitrogen and age were higher in nonsurvivors than survivors. At 4 hours, IL-8, IL-10, and IL1-ra levels were higher in nonsurvivors than in survivors; t-SOFA was also higher and peaked on day 3 in nonsurvivors. Only IL-8 levels on day 1 were significantly associated with a t-SOFA > or =10 on day 3 (odds ratio 1.10, 95% confidence interval 1.01-1.21, p = 0.04). Neopterin, marker of monocyte activation, increased significantly only in nonsurvivors (p < 0.001). These findings suggest that an activated inflammatory system soon after LVAD implant is implicated in MOFS development. Early monitoring of inflammatory mediators and t-SOFA score may be a valuable tool for outcome prediction in LVAD recipients.

Cellular immunity impaired among patients on left ventricular assist device for 6 months

BACKGROUND

Sustained maintenance on left ventricular assist device (LVAD) is associated with an increased frequency of severe infections. Although temporary changes in cellular immunity are seen immediately after implantation, the consequence of sustained LVAD treatment on immunity is unknown.

METHODS

In vitro functional and phenotypic markers of T cell activation and 6 month clinical outcome were compared between patients with > or = 6-month LVAD therapy and heart failure control patients.

RESULTS

Recipients of LVADs had more infections (45.5% versus 0%; p < 0.05) and mortality (54% versus 16%; p < 0.05) than control patients. T-cell proliferative responses were lower among LVAD recipients than control patients when challenged with phytohemagglutinin (3.4 +/- 4.7 versus 28.5 +/- 19.6; p < 0.01), anti-CD3 (4.3 +/- 4.5 versus 16.4 +/- 17; p < 0.01), and staphylococcal enterotoxin B (7.2 +/- 6.3 versus 26.1 +/- 15.6; p = 0.002). Proliferative hyporesponsiveness among LVAD recipients was not caused by apoptosis (2.6% +/- 2.7% versus 2.7% +/- 2.1%; p = 0.94) or insufficient CD4+ cells (42.1% +/- 11.3% versus 40.2% +/- 7.5%; p = 0.71) relative to control patients. Instead, CD3+ cells from LVAD patients expressed less interleukin 2 (2.5% +/- 1.5% versus 5.2% +/- 3.1%; p = 0.03) and tumor necrosis factor-alpha (6.0% +/- 3.5% versus 25.8% +/- 8.7%; p < 0.001) and more interleukin 10 (5.8% +/- 6.1% versus 2.6% +/- 2.1%; p < 0.05). In addition, suppressive T-regulatory cells were more prevalent in LVAD patients than control patients (12.9% +/- 3.2% versus 1.2% +/- 1.1%; p < 0.001).

CONCLUSIONS

Cellular immunity is compromised among long-term LVAD recipients because of a downregulatory cytokine imbalance and emergence of suppressive T-regulatory cells.

Prevalence and risks of allosensitization in HeartMate left ventricular assist device recipients: The impact of leukofiltered cellular blood product transfusions

OBJECTIVE

Allosensitization of left ventricular assist device recipients has been associated with perioperative transfusion of cellular blood products. The relative sensitizing contribution of leukofiltered cellular blood products, however, remains unclear. We investigated the pattern of sensitization in left ventricular assist device recipients in relation to cellular blood product transfusions received.

METHODS

Seventy-one consecutive nonsensitized recipients of the HeartMate left ventricular assist device (Thoratec Corporation, Pleasanton, Calif) as a bridge to transplantation were reviewed. Panel-reactive HLA antibody levels at consecutive times after device implantation were correlated with perioperative cellular blood product transfusions.

RESULTS

Fifty-four patients received leukofiltered cellular blood products (transfused), whereas 17 patients received only fresh-frozen plasma (nontransfused). Among nontransfused patients, 58.8% (10/17) became sensitized during mechanical support, versus 35.2% of transfused patients (19/54, P = .15). There was a trend toward more sensitization during the 12 weeks after device placement in nontransfused patients. Kaplan-Meier analysis revealed significantly more sensitization in nontransfused patients than in transfused patients, despite equal rates of transplantation (P = .05). A dose-response analysis revealed significant trends toward less sensitization and lower peak panel-reactive antibody level with more cellular blood product transfusions (P = .04). Multivariate Cox regression revealed only increasing transfusions to be associated with a reduced risk of sensitization (hazard ratio 0.18, P = .01).

CONCLUSIONS

Sensitization becomes more prevalent with increasing length of support. Avoidance of perioperative leukocyte-filtered cellular blood product transfusions does not decrease the incidence or degree of HLA sensitization. Conversely, cellular blood product transfusions may be associated with lessened alloimmunization and may mitigate the sensitization seen in recipients of the HeartMate left ventricular assist device as a bridge to transplantation.

Intravascular Device Infections

Intravascular devices such as pacemakers, implantable cardioverter-defibrillators (ICDs), left ventricular assist devices (LVADs), and prosthetic vascular grafts are life-saving therapies for patients with malignant arrhythmias, heart failure, and various vascular diseases. As indications for their use have increased, so has the prevalence of infectious complications associated with these devices. We present a review of the clinical literature on the epidemiology, diagnosis, and management of infectious complications of these intravascular devices. Most intravascular device infections are thought to result from skin flora contamination during implantation. Infection of the subcutaneous portion of the device can subsequently track to deeper intravascular tissues. Infection that involves the intravascular or intracardiac portion of these devices carries a high morbidity and mortality. Despite appropriate antibiotic therapy, cure of infection is frequently possible only with device removal. Well-designed placebo-controlled, randomized studies evaluating antimicrobial therapy for treatment of intravascular device infections are lacking. In the absence of better information, authorities recommend antibiotics targeted toward cultured organisms for approximately 4 to 6 weeks and device removal.

Low-Dose Prophylactic Intravenous Immunoglobulin Does Not Prevent HLA Sensitization in Left Ventricular Assist Device Recipients

BACKGROUND

The use of left ventricular assist devices is associated with human leukocyte antigen (HLA) allosensitization. We investigated whether prophylactic treatment with low-dose intravenous immunoglobulin (IVIG), analogous to the use of IgG anti-D (anti-Rh) in preventing Rh immunization, can abrogate HLA allosensitization after left ventricular assist device implantation.

METHODS

We retrospectively reviewed the data from 84 consecutive heart failure patients who underwent implantation of a left ventricular assist device as a bridge to transplantation. After implantation, panel reactive antibody (PRA) was measured biweekly to assess sensitization (defined by PRA > 10%). Patients who were sensitized before left ventricular assist device implantation were excluded from further analysis (n = 12). Patients who either did not require perioperatively transfusions of cellular blood products or received other immunomodifying regimens were also excluded from further analysis (n = 21). The rest of the patients were divided into two groups based on whether they received IVIG, 10 g daily for 3 days (IVIG group, n = 26; non-IVIG group, n = 25). The decision as to whether patients received IVIG was not randomized but was based on surgeon preference.

RESULTS

The sensitization rates (expressed as ratio of sensitized patients to total patients at risk) in the two groups were similar at consecutive time points (2, 4, 6, 8, 12, 20 weeks) after left ventricular assist device implantation. Also, mean PRA at the same time points did not differ between the two groups. Overall, 34.6% (9 of 26) of the IVIG group became sensitized during mechanical support, compared with 32% (8 of 25) of the non-IVIG group (p = 1.0). A PRA of 90% or greater (high-degree sensitization) occurred in 15.3% (4 of 26) of the IVIG group and 12.0% (3 of 25) of the non-IVIG group (p = 0.5).

CONCLUSIONS

The use of low-dose prophylactic IVIG after left ventricular assist device implantation affects neither the incidence nor the severity of HLA allosensitization.

The Impact of Hypogammaglobulinemia on Infection Outcome in Patients Undergoing Ventricular Assist Device Implantation

BACKGROUND

Infection is a major comorbidity after ventricular assist device (VAD) placement. Defects in cellular immunity have been reported after VAD placement. However, to our knowledge, quantitative immunoglobulin G (IgG) level determination and the impact of hypogammaglobulinemia (HGG) on infections after VAD implantation have not been evaluated before.

METHODS

A total of 76 patients (mean age, 53 years) underwent VAD implantation as a bridge to transplantation and had IgG levels determined as a baseline before transplantation. Patients were divided into 2 groups according to IgG level: Control Group (n = 56, IgG > or = 700 mg/dl) and HGG Group (n = 20, IgG < 700 mg/dl). Infection outcome during the VAD course and after transplantation was analyzed in relation to the IgG level.

RESULTS

Baseline characteristics were similar in both groups. The incidence of bacteremia (14/20 [70%] vs 18/56 [32%], p = 0.0032) and major infection (19/20 [95%] vs 31/56 [56%], p = 0.0009) were significantly increased in the HGG Group compared with the Control Group. After transplantation, the episodes of rejection were similar in both groups and survival was similar. The HGG Group experienced more cytomegalovirus infections compared with the Control Group (9/20 [45%] vs 9/56 [16%], p = 0.009).

CONCLUSIONS

VAD patients with HGG are at increased risk of infections. After transplantation, these patients also experience increased cytomegalovirus infections. A randomized preemptive IgG replacement trial may be warranted in the future to determine if this intervention will alleviate the risk of infection.

Sensitization following LVAD implantation using leucodepleted blood is not due to HLA antibodies

Implantation of left ventricular assist devices (LVAD) is associated with HLA antibody sensitization. The objective of this study was to determine the specificity of antibodies produced by LVAD recipients using a combination of ELISA, Luminex and microcytotoxicity assays. Fifty-one LVAD patients were studied, from 44 to 838 days post-implantation. No patient developed HLA antibodies, although 24 produced IgG antibodies detectable in both ELISA and Luminex assays. These antibodies manifest as positive reactions with class I and class II wells of the ELISA and also blank wells. In Luminex assays, they produce high MFI readings with the negative control beads. Antibodies were detected 18 to 228 days after implantation. This reactivity was found to be directed against bovine serum albumin (BSA), commonly used to block non-specific binding in ELISA and Luminex assays; absorption of sera with BSA-coated beads completely abrogated reactivity in all solid phase assays, but did not eliminate anti-HLA antibodies in control sera. Ten of the 24 patients have proceeded to transplantation, with a 1-year graft survival of 69%. In conclusion, it appears that implantation of LVADS disrupts immunoregulatory pathways leading to production of anti-albumin antibodies. These can be misinterpreted as anti-HLA antibodies in solid phase assays.

Perioperative management of ventricular assist devices in children and adolescents

Ventricular assist devices are an integral part of therapy for patients with end-stage heart failure. Devices can either bridge to recovery or to transplantation. Options for ventricular assist devices include those that are centrifugal, pulsatile, and new rotary/axial devices. Care of the patient on a ventricular assist device is multifaceted, involving pharmacologic or mechanical support of the right ventricle, management of systemic vascular resistance, and manipulation of the hematologic system to avoid bleeding or thrombosis. In addition, care of these patients involves support of all end organs and avoidance of infectious complications. Care of these patients is complex, requiring a highly integrated team for optimal outcome.

Multicenter experience: prevention and management of left ventricular assist device infections

Implantable left ventricular assist devices (LVADs) have demonstrated clinical success in both the bridge-to-transplantation and destination-therapy patient populations; however, infection remains one of the most common causes of mortality during mechanical circulatory support. Thus, serious LVAD infections may negate the benefits of LVAD implantation, resulting in decreased quality of life, increased morbidity and mortality, and increased costs associated with implantation. Prevention of device-related infection is crucial to the cost-effective use of mechanical circulatory support devices. Therefore, adherence to evidence-based infection control and prevention guidelines, meticulous surgical technique and optimal postoperative surgical site care form the foundation for LVAD associated infection prevention.

Relationship between bridging with ventricular assist device on rejection after heart transplantation

BACKGROUND

Ventricular assist devices (VADs) are commonly used to bridge patients to heart transplantation. Recipients of VADs may develop anti-human histocompatibility leukocyte antigen antibodies, as reflected by elevated panel-reactive antibodies (PRA). The purpose of this study was to evaluate the relationship between bridging with VAD before heart transplantation and development of cellular rejection, humoral rejection, and allograft vasculopathy after transplantation.

METHODS

Data on all patients who underwent cardiac transplantation between July 1994 and February 2001 at Rush Presbyterian St Luke's Medical Center were retrospectively reviewed. Data collected included sex, age, etiology of cardiomyopathy, percentage panel reactive antibodies (by cytotoxic method), type and duration of mechanical circulatory support, transfusion history, rejection history (both cellular and humoral) after cardiac transplantation, and development of allograft vasculopathy. Cellular rejection was treated when International Society of Heart and Lung and Transplantation Grade 2 or greater in the first 12 months after transplant and Grade 3 or greater after 12 months and treated with intensification of immunosuppression. Humoral rejection was defined clinically as allograft dysfunction by echocardiography without evidence of cellular rejection on endomyocardial biopsy or allograft vasculopathy. Allograft vasculopathy was defined by presence of any degree of luminal narrowing or pruning of distal vessels by coronary arteriography. Statistical analyses were performed by chi-square test, Fisher's exact test, and Wilcoxon rank sum test, as appropriate.

RESULTS

Ninety-eight patients underwent cardiac transplantation during the study period (87 men, mean age 49 years, 46 ischemic etiology). Of these, 48 were bridged with HeartMate VAD (20 patients received vented electric device, 28 received pneumatic device). Nineteen percent of VAD patients had a peak pretransplant PRA > or =10% vs 2% of patients without VAD (p = 0.014). PRA > or =10%, use of VAD, or duration of VAD support did not predict development of humoral rejection. Use of VAD did not predict development of cellular rejection or allograft vasculopathy. VAD use was not associated with sudden death after heart transplantation. In the entire group of 98 patients, neither humoral nor cellular rejection predicted development of allograft vasculopathy. Longer ischemic time correlated with increased cellular rejection and humoral rejection after transplantation (p = 0.01).

CONCLUSIONS

Some patients bridged to cardiac transplantation with VADs have increased PRA before heart transplantation, but this does not appear to translate into increased risk of either humoral or cellular rejection after transplantation or development of allograft vasculopathy as detected by coronary angiography.

L'activation sanguine au cours de l'assistance circulatoire mécanique prolongée

Mechanical circulatory support has become an approved treatment option for patients with cardiogenic shock or end-stage heart failure. However, recipients of heart assist devices are prone to high incidences of bleeding, thrombo-embolic and infectious complications. The occurrence of these complications is favoured by systemic alterations of coagulation and fibrinolysis, inflammation and immune responses. Several studies have evaluated these pathophysiological changes in patients undergoing long term circulatory support with pulsatile devices. However, the systemic consequences of the more recently introduced rotary blood pumps remain largely unknown. The present review focuses on the systemic consequences of long term circulatory support with pulsatile and non-pulsatile devices.

Sideroblastic anemia due to linezolid in a patient with a left ventricular assist device

An acquired form of sideroblastic anemia has been described in association with several drugs, especially anti-microbial agents. A case of sideroblastic anemia is presented in a patient with a left ventricular assist device drive-line infection who was receiving linezolid, an antibiotic used for serious infections with gram-positive organisms. This patient's anemia resolved after discontinuation of the drug; he subsequently underwent an uncomplicated orthotopic heart transplant with no recurrence of anemia. As linezolid has been shown to have hematologic side effects, blood count monitoring is recommended in patients receiving this drug for long-term therapy.

HLA sensitization in ventricular assist device recipients: does type of device make a difference?

BACKGROUND

We sought to (1) characterize the temporal pattern of T-cell panel reactive antibody during ventricular assist device support, (2) identify predictors of higher T-cell panel reactive antibody during ventricular assist device support, and (3) determine whether device type remained a predictor after accounting for nonrandom device selection.

METHODS

Between December 1991 and August 2000, 239 patients received implantable ventricular assist devices, of whom 231 had T-cell panel reactive antibody measured. Panel reactive antibody was measured before implantation of the assist device, approximately 2 weeks after device implantation, irregularly thereafter depending on clinical events and length of support, and at transplantation. Longitudinal mixed modeling was used to characterize the temporal pattern of sensitization and its predictors during ventricular assist device support. To account for nonrandom factors in device selection when comparing HeartMate (Thermo Cardiosystems, Inc, Woburn, Mass) and Novacor (Baxter Healthcare Corp, Novacor Div, Oakland, Calif) devices, we propensity-matched patients according to baseline characteristics.

RESULTS

T-cell panel reactive antibody increased rapidly after implantation of the ventricular assist device and then immediately began to decrease. Predictors of higher T-cell panel reactive antibody during support with the assist device were a shorter interval from device implantation to T-cell panel reactive antibody measurement (P <.0001), female sex (P =.0004), younger age (P =.01), higher T-cell panel reactive antibody before device implantation (P =.03), more perioperative red blood cell transfusions (P =.006), and an earlier date of device implantation (P =.001). In matched patients, device type was not a predictor of higher T-cell panel reactive antibody during ventricular assist device support (P =.8).

CONCLUSIONS

HLA sensitization during ventricular assist device support is not constant but increases rapidly at implantation and then decreases. This temporal pattern of sensitization is influenced by patient factors and not by the type of device.

What price support? Ventricular assist device induced systemic response

Use of ventricular support systems has been associated with myriad systemic complications. Engendered by the blood-biomaterial interface of a unique host/device relationship, these complications include diverse humoral dyscrasias that frequently culminate in episodes of bleeding, hemolysis and thrombogenicity, heightened susceptibility to inflammation and infection, and transient immunal compromise. Recent endeavor in biocompatibility research has served to illustrate the critical role played by cellular, humoral, and neurohormonal components in regulating cytokine expression and has provided insight into the complexities involved in such biomechanical juxtapositions. The following is intended as a review of current literature attempting to address the many aspects of this host/device interaction and their consequences for the supported patient.

Outcome of patients surviving to heart transplantation after being mechanically bridged for more than 100 days

OBJECTIVE

The effect of long-term mechanical support on subsequent heart transplantation is still debated.

METHODS

We report the outcome of 41 patients (42 +/- 12 years) bridged with left ventricular assist devices (VAD; 28 Novacor, 9 HeartMate, 2 Thoratec, and 2 DeBakey) for >100 days (218 +/- 76 days) between April 1994 and March 2000). We compared follow-up with 146 patients (55 +/- 13 years) who underwent heart transplantation during the same time without prior long-term mechanical support.

RESULTS

Thirty-two of the 41 patients (78%) underwent heart transplantation, 9 patients (22%) died of multi-organ (n = 5), cardiac (n = 2), or cerebral failure (n = 2). Thirty-day post-transplant mortality includes 5 cases (3 graft failures). Within the following 2 years, another 5 patients expired, 2 of cardiac failure/sudden death. Currently, 21 of 41 patients (51%) are still alive 10 to 77 months (41 +/- 22 months) after heart transplantation (1 patient was lost for follow-up). One-year and 5-year survival rates were compared with the control group (VAD vs control, 1-year survival was 75% vs 74% and 5-year survival was 60% vs 66%). Fifteen patients are doing well in New York Heart Association Class I), and 6 are NYHA Class II despite normal left ventricular ejection fraction. Episodes of moderate acute rejection (International Society for Heart and Lung Transplantation Grade 3) occurred in 10 patients (1.3 episodes per patient), not significantly different from that of the control group (1.2 episodes per patient). Scintigraphy showed regional myocardial ischemia/transplant vasculopathy in 4 patients, and coronary angiography detected the same in 2. One patient has undergone successful retransplantation. Two patients had increased right ventricular pressure. Six patients had impaired kidney function, and 3 had impaired liver function. Seven patients experienced cytomegalovirus infection.

CONCLUSIONS

Our data indicate that patients who underwent heart transplantation after long-term mechanical support have a similar survival rate and comparable cardiac morbidity associated with acute rejection episodes.

Systemic consequences of ventricular assist devices: alterations of coagulation, immune function, inflammation, and the neuroendocrine system

Implantable ventricular assist devices have proven efficacious as a bridge to transplantation and as a bridge to recovery. Although current indications for use of assist devices are somewhat limited, they are likely to expand in the upcoming years, including their use as destination therapy for end-stage heart failure. Recipients of assist devices, however, are prone to certain device-specific complications, including excessive postoperative bleeding, late propensity for thromboembolism, infections, and systemic inflammation, which may contribute to end-organ dysfunction. This article reviews the systemic biochemical alterations underlying these clinical phenomena. As assist devices are increasingly used, better understanding of these systemic perturbations is imperative.

HLA alloimmunization in patients requiring ventricular assist device support

BACKGROUND

Ventricular assist devices (VADs) are often necessary to maintain circulation in patients with heart failure prior to cardiac transplantation. However, the use of such devices has been reported to be associated with a high incidence of development of human leukocyte antigen (HLA) antibodies, due perhaps, according to some investigators, to immune-activating properties of the VAD itself. We looked at HLA antibody formation in our patients during VAD support to determine the rate and potential causes of antibody formation.

METHODS

Between 1995 and 2000, 54 patients were placed on a VAD at our institution. We reviewed clinical and blood transfusion history and HLA antibody testing of the 29 patients without HLA antibodies prior to implantation. HLA antibody testing was performed by an anti-globulin-augmented cytotoxicity method or by a commercial enzyme-linked immunoassay (ELISA) kit.

RESULTS

Eight of 29 patients (28%) developed HLA antibodies. Patients who developed HLA antibodies after VAD implantation received significantly more total peri- and post-operative transfusions than did those who remained negative (99 transfusions vs 34 transfusions, p = 0.0014). Within this small study group, gender, age, etiology of heart failure, previous cardiac surgery and duration of VAD support showed no statistically significant correlation with formation of HLA antibodies.

CONCLUSIONS

Our data suggest that HLA alloimmunization during VAD support may be due to extensive blood transfusion. The rate of HLA alloimmunization does not appear to be greater than that reported in other populations of multi-transfused patients. Leukoreduction of cellular components, as well as plasma, or other initiatives is needed to reduce the rate of alloimmunization and, potentially, the wait to transplantation.

Nonvalvular Intravascular Device-related Infections

Nonvalvular intravascular devices are in widespread use in developed countries and are now more commonly employed than are prosthetic cardiac valves. Although the variety of devices that are included in the category of "nonvalvular" represent a heterogenous collection, there is commonality among several of the devices. This includes their requirement to sustain life and the need for removal for cure if they become infected, which is often due to multidrug-resistant microorganisms. Thus, infection of these devices often presents difficult treatment scenarios. This update will address the pathogenesis and immunobiology of nonvalvular intravascular device-related infections and the epidemiology and treatment of infections of several of these devices that include pacemakers, implantable cardioverter defibrillators, intravascular catheters, vascular grafts and stents, and left ventricular assist devices.

Preformed anti-human leukocyte antigen antibodies jeopardize cardiac transplantation in patients with a left ventricular assist device

In 1997, 15% of patients who received a cardiac transplant in the United States needed a mechanical circulatory support device before transplantation. One device that patients received was the left ventricular assist device (LVAD). During the LVAD support period, approximately 30% to 80% of LVAD recipients have positive test results for panel reactive antibodies (PRAs). Many of these antibodies form against human leukocyte antigens (HLA). These antigens are present on most cells and stimulate antibody production when a person receives unrelated donor cells. Several pre-LVAD and post-LVAD factors contribute to anti-HLA antibody formation. These antibody levels must be lowered before transplantation because the presence of anti-HLA antibodies makes it more difficult to find a suitable donor and increases the risk of rejection. The objectives of this article are to describe anti-HLA antibody formation in LVAD recipients, review its major consequences and treatments, and discuss nursing actions associated with anti-HLA antibody formation.

Advanced mechanical circulatory support with the HeartMate left ventricular assist device in the year 2000

This paper describes the HeartMate left ventricular assist device (ThermoCardiosystems Inc, Woburn, MA) technology, which has been successfully introduced into the clinical arena with more than 2,400 implants as of the year 2000. The review summarizes the clinical experience, and identifies the benefits and limitations of the current state-of-the-art technology of the leading implantable circulatory support system.