Influence of durable mechanical circulatory support and allosensitization on mortality after heart transplantation

Effectiveness of combined plasma cell therapy and costimulation blockade based desensitization regimen in heart transplant candidates

BACKGROUND

Desensitization is one of the strategies to reduce antibodies and facilitate heart transplantation in highly sensitized patients. We describe our center's desensitization experience with combination of plasma cell (PC) depletion therapy (with proteasome inhibitor or daratumumab) and costimulation blockade (with belatacept).

METHODS

We reviewed five highly sensitized patients who underwent desensitization therapy with plasma cell depletion and costimulation blockade. We evaluated the response to therapy by measuring the changes in cPRA, average MFI, and number of positive beads > 5000MFI.

RESULTS

Five patients, mean age of 56 (37-66) years with average cPRA of 98% at 5000 MFI underwent desensitization therapy. After desensitization, mean cPRA decreased from 98% to 70% (p = .09), average number of beads > 5000 MFI decreased from 59 to 37 (p = .15), and average MFI of beads > 5000 MFI decreased from 16713 to 13074 (p = .26).

CONCLUSION

Combined PC depletion and CoB could be a reasonable strategy for sustained reduction in antibodies in highly sensitized patients being listed for heart transplantation.

Association between calculated panel reactive antibody and waitlist outcomes in the 2018 heart allocation system

BACKGROUND

The impact of heart transplant (HT) waitlist candidate sensitization on waitlist outcomes in the US is unknown.

METHODS

Adult waitlist outcomes in OPTN (October 2018-September 2022) by calculated panel reactive antibody (cPRA) were modeled to identify thresholds of clinical significance. The primary outcome was the rate of HT by cPRA category (low: 0-35, middle: >35-90, high: >90) assessed using multivariable competing risk analysis (compete: waitlist removal for death or clinical deterioration). The secondary outcome was waitlist removal for death or clinical deterioration.

RESULTS

The elevated cPRA categories were associated with lower rates of HT. Candidates in the middle (35-90) and high cPRA categories (>90) had an adjusted 24% lower rate (hazard ratio (HR) 0.86, 95% confidence interval (CI) 0.80-0.92) and 61% lower rate (HR 0.39 95% CI. 0.33-0.47) of HT than the lowest category, respectively. Waitlist candidates in the high cPRA category listed in the top acuity strata (Statuses 1, 2) had increased rates of delisting for death or deterioration compared to those in the low cPRA category (adjusted HR 2.9, 95% CI 1.5-5.5), however, elevated cPRA (middle, high) was not associated with an increased rate of death and delisting when the cohort was considered as a whole.

CONCLUSIONS

Elevated cPRA was associated with reduced rates of HT across all waitlist acuity tiers. Among HT waitlist candidates listed at the top acuity strata, the high cPRA category was associated with increased rates of delisting due to death or deterioration. Elevated cPRA may require consideration for critically ill candidates under continuous allocation.

Management of the sensitized heart transplant candidate

PURPOSE OF REVIEW

For sensitized heart transplant candidates who have antibodies to human leukocyte antigens (HLA), finding a suitable donor can be challenging and can lead to adverse waitlist outcomes. In recent years, the number of sensitized patients awaiting heart transplantation 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.

RECENT FINDINGS

Advances in the assessment of HLA antibodies allow for identification of heart transplant candidates who may benefit from desensitization strategies to widen the donor pool and mitigate the risk of adverse posttransplant outcomes.

SUMMARY

Antibody sensitization is a barrier to successful heart transplantation and strategies to identify sensitized patients, stratify their risk, and mitigate this risk through desensitization is crucial to optimize the quality of life and survival of HT recipients.

Effect of the UNOS policy change on rates of rejection, infection, and hospital readmission following heart transplantation

BACKGROUND

The 2018 adult heart allocation policy sought to improve waitlist risk stratification, reduce waitlist mortality, and increase organ access. This system prioritized patients at greatest risk for waitlist mortality, especially individuals requiring temporary mechanical circulatory support (tMCS). Posttransplant complications are significantly higher in patients on tMCS before transplantation, and early posttransplant complications impact long-term mortality. We sought to determine if policy change affected early posttransplant complication rates of rejection, infection, and hospitalization.

METHODS

We included all adult, heart-only, single-organ heart transplant recipients from the UNOS registry with pre-policy (PRE) individuals transplanted between November 1, 2016, and October 31, 2017, and post-policy (POST) between November 1, 2018, and October 31, 2019. We used a multivariable logistic regression analysis to assess the effect of policy change on posttransplant rejection, infection, and hospitalization. Two COVID-19 eras (2019-2020, 2020-2021) were included in our analysis.

RESULTS

The majority of baseline characteristics were comparable between PRE and POST era recipients. The odds of treated rejection (p = 0.8), hospitalization (p = 0.69), and hospitalization due to rejection (p = 0.76) and infection (p = 0.66) were similar between PRE and POST eras; there was a trend towards reduced odds of rejection (p = 0.08). In both COVID eras, there was a clear reduction in rejection and treated rejection with no effect on hospitalization for rejection or infection. Odds of all-cause hospitalization was increased in both COVID eras.

CONCLUSIONS

The UNOS policy change improves access to heart transplantation for higher acuity patients without increasing early posttransplant rates of treated rejection or hospitalization for rejection or infection, factors which portend risk for long-term posttransplant mortality.

Selection and Interpretation of Molecular Diagnostics in Heart Transplantation

The number of heart transplants performed annually in the United States and worldwide continues to increase, but there has been little change in graft longevity and patient survival over the past 2 decades. The reference standard for diagnosis of acute cellular and antibody-mediated rejection includes histologic and immunofluorescence evaluation of endomyocardial biopsy samples, despite invasiveness and high interrater variability for grading histologic rejection. Circulating biomarkers and molecular diagnostics have shown substantial predictive value in rejection monitoring, and emerging data support their use in diagnosing other posttransplant complications. The use of genomic (cell-free DNA), transcriptomic (mRNA and microRNA profiling), and proteomic (protein expression quantitation) methodologies in diagnosis of these posttransplant outcomes has been evaluated with varying levels of evidence. In parallel, growing knowledge about the genetically mediated immune response leading to rejection (immunogenetics) has enhanced understanding of antibody-mediated rejection, associated graft dysfunction, and death. Antibodies to donor human leukocyte antigens and the technology available to evaluate these antibodies continues to evolve. This review aims to provide an overview of biomarker and immunologic tests used to diagnose posttransplant complications. This includes a discussion of pediatric heart transplantation and the disparate rates of rejection and death experienced by Black patients receiving a heart transplant. This review describes diagnostic modalities that are available and used after transplant and the landscape of future investigations needed to enhance patient outcomes after heart transplantation.

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.

Elevated Plasma Immunoglobulin Levels Prior to Heart Transplantation Are Associated with Poor Post-Transplantation Survival

Cardiac allograft vasculopathy (CAV) and antibody-mediated rejection are immune-mediated, long-term complications that jeopardize graft survival after heart transplantation (HTx). Interestingly, increased plasma levels of immunoglobulins have been found in end-stage heart failure (HF) patients prior to HTx. In this study, we aimed to determine whether increased circulating immunoglobulin levels prior to transplantation are associated with poor post-HTx survival. Pre-and post-HTx plasma samples of 36 cardiac transplant recipient patients were used to determine circulating immunoglobulin levels. In addition, epicardial tissue was collected to determine immunoglobulin deposition in cardiac tissue and assess signs and severity of graft rejection. High levels of IgG1 and IgG2 prior to HTx were associated with a shorter survival post-HTx. Immunoglobulin deposition in cardiac tissue was significantly elevated in patients with a survival of less than 3 years. Patients with high plasma IgG levels pre-HTx also had significantly higher plasma levels after HTx. Furthermore, high pre-HTX levels of IgG1 and IgG2 levels were also significantly increased in patients with inflammatory infiltrate in CAV lesions. Altogether the results of this proof-of-concept study suggest that an activated immune response prior to transplantation negatively affects graft survival.

Impact of duration of mechanical support on heart transplantation: Hasty transplantation may not have a good long-term outcome

BACKGROUND

Mechanical circulatory support (MCS) has been widely utilized in critically ill cardiac transplant candidates. Few studies have investigated the impact of duration of MCS before heart transplantation (HTx) on long-term patient survival.

METHODS

A retrospective HTx database was reviewed between 2009 and 2019. Patients who did not or did undergo MCS before HTx were categorized into two groups: (1) A (did not) and (2) B (did), respectively. A receiver operating characteristic (ROC) curve was plotted to assess the cutoff level of MCS duration before HTx in evaluating 5-year survival.

RESULT

A total of 270 HTx patients (group A: 120, group B: 150) were analyzed. Group B patients had a higher percentage of blood type O, a higher incidence of resuscitation, a shorter listing duration, and a higher likelihood of having United Network for Organ Sharing (UNOS) 1A status than group A. The ROC curve revealed 24 days as a good cut-off level for determining the best MCS before HTx timing. Group B was categorized into two subgroups: (1) B1 (MCS < 24 days, n = 65) and (2) B2 (MCS > 24 days, n = 85). B2 had a higher incidence of cardiopulmonary resuscitation (CPR), hemodialysis, longer waiting time after MCS, and better ventricular assist device implantation than B1. However, the survival curves showed that B1 outcomes were significantly worse than in groups A and B2. Groups A and B2 had similar survival curves without an increased incidence of infection.

CONCLUSION

The preliminary data demonstrated that a longer duration of MCS may be associated with better outcomes than urgent HTx.

Sensitization during short-term mechanical circulatory support. Determinants, therapeutic management, and outcomes after heart transplant

INTRODUCTION AND OBJECTIVES

The development of human-leukocyte antigen antibodies is a well-known adverse effect of the use of long-term ventricular assist devices (VADs). The aim of this study was to determine the incidence of sensitization during short-term mechanical circulatory support with VAD (CentriMag), its determinants, and its impact on posttransplant outcomes.

METHODS

We performed a retrospective review of patients who were bridged to transplant with short-term VAD from 2009 to 2019. Sensitization was defined as a calculated panel-reactive antibody> 10%. The endpoints included overall survival and rejection-free survival.

RESULTS

A total of 89 patients (median age 56.0 [interquartile range, 50.0-59.9] years, 16.8% female) received a short-term VAD as a bridge to transplant. The median duration of support was 23.6 [interquartile range, 16.6-35.0] days. Eleven patients (12.4%) became sensitized during support. The only factor significantly associated with sensitization was female sex (OR, 8.67; 95%CI, 1.93-38.8; P=.005). Of the 89 patients, 21 patients died during support; 68 patients underwent heart transplant. After a mean follow-up of 49.6 ±31.2 months, 8 patients (11.8%) died and 20 (29.4%) had at least 1 rejection episode. On multivariate analysis, sensitization was an independent predictor of acute rejection (HR, 3.64; 95%CI, 1.42-9.33; P=.007), with a nonstatistically significant trend to higher mortality (HR, 4.07; 95%CI, 0.96-17.3; P=.057).

CONCLUSIONS

Sensitization with short-term VADs can occur and is significantly associated with female sex and with rejection. Sensitization also showed a nonstatistically significant trend to higher mortality.

De Novo Human Leukocyte Antigen Allosensitization in Heartmate 3 Versus Heartmate II Left Ventricular Assist Device Recipients

Left ventricular assist devices (LVADs) are associated with the development of antihuman leukocyte antigen (HLA) antibodies, which can create a challenge for future transplantation in these patients. The differential effects of Heartmate 3 (HM3) versus Heartmate II (HMII) on de novo HLA allosensitization remain unknown. Patients who underwent HMII or HM3 implantation and had no prior HLA antibodies by solid-phase assay (Luminex) testing were included in this study. Complement-dependent cytotoxicity (CDC) panel reactive antibody (PRA) levels and Luminex antibody profiles were followed until cardiac transplantation, device explantation, or death. Electronic medical records were reviewed to examine posttransplant outcomes. Thirty-eight HM3 and 34 HMII patients with complete data were followed for 1.5 ± 1.1 years on device support. HM3 and HMII groups had similar age at implant, female gender, ischemic heart failure etiology, bridge strategy at implant, as well as intraoperative and postoperative transfusion requirements. 39.5% of HM3 and 47.1% of HMII patients developed detectable HLA antibodies by Luminex testing (p = 0.516). Development of high-level (mean fluorescence intensity >10,000) antibodies was significantly lower in HM3 than HMII patients (5.3 vs. 20.6%, p = 0.049). CDC PRA testing showed fewer HM3 patients with a positive result (PRA > 0%) than HMII patients (39.4 vs. 70.0%, p = 0.015). Among transplanted patients, those who had developed de novo sensitization on LVAD support showed a trend toward incidence of moderate to severe grade rejection compared with unsensitized patients (23.8 vs. 4.8%, p = 0.078). HM3 is associated with lower risk of de novo HLA sensitization compared with HMII.

Impact of the Pre-Transplant Circulatory Supportive Strategy on Post-Transplant Outcome: Double Bridge May Work

Background: The number of waitlisted patients requiring mechanical circulatory support (MCS) as a bridge to heart transplantation is increasing. The data concerning the results of the double-bridge strategy are limited. We sought to investigate the post-transplant outcomes across the different bridge strategies. Methods: We retrospectively reviewed a heart transplantation database from Jan 2009 to Jan 2019. Intra-aortic balloon pump (IABP), extracorporeal membrane oxygenation (ECMO), and ventricular assist devices (VAD) were the MCS that we investigated. The pre- and post-transplant characteristics and variables of patients bridged with the different types of MCS were collected. The post-transplant survival was compared using Kaplan–Meier survival analysis. Results: A total of 251 heart transplants were reviewed; 115 without MCS and 136 with MCS. The patients were divided to five groups: Group 1 (no MCS): n = 115; Group 2 (IABP): n = 15; Group 3 (ECMO): n = 33; Group 4 (ECMO-VAD): double-bridge (n = 59); Group 5 (VAD): n = 29. Survival analysis demonstrated that the 3-year post-transplant survival rates were significantly different among the groups (Log-rank p < 0.001). There was no difference in survival between group 4(ECMO-VAD) and group 1(no MCS)1 (p = 0.136), or between group 4(ECMO-VAD) and group 5(VAD) (p = 0.994). Group 3(ECMO) had significantly inferior 3-year survival than group 4(ECMO-VAD) and group 5(VAD). Conclusion: Double bridge may not lead to worse mid-term results in patients who could receive a transplantation. Initial stabilization with ECMO for critical patients before implantation of VAD might be considered as a strategy for obtaining an optimal post-transplant outcome.

The effect of paracorporeal pulsatile biventricular assist devices on allosensitization in adults: A comparison with left ventricular assist devices

Ventricular assist devices (VADs) have been associated with the development of anti-HLA antibodies ('allosensitization'), but data on devices providing biventricular support in adults are limited. We sought to characterize differences in anti-HLA antibody formation in adult patients receiving left- (LVAD) versus biventricular- (BiVAD) assist devices as bridge to transplantation (BTT) by retrospectively reviewing the records of adult patients who have undergone VAD implantation at our institution. We assessed 82 patients supported with a pulsatile-flow paracorporeal BiVAD and compared them with 40 patients receiving LVAD till 2018. Forty-eight (58.5%) of the BiVAD and 23 (57.5%) of the LVAD patients were eventually transplanted (p = 0.91) with an average time to transplantation 559 and 598 days, respectively (p = 0.73). Evidence of sensitization pre-VAD was found in 11.0% of the BiVAD patients and 15.0% of the LVAD ones (p = 0.53); these percentages rose to 43.9% (p < 0.001) and 40.0% (p = 0.01), respectively. The post-VAD sensitization status was not significantly different between the BiVAD and the LVAD group (p = 0.68). De novo sensitization was comparable between the two groups (p = 0.55). Post-transplantation outcomes regarding rejections and cardiac allograft vasculopathy were also similar. Conclusively, BiVAD- and LVAD- induced allosensitization do not appear to differ significantly.

The effects of donor-specific antibody characteristics on cardiac allograft vasculopathy

BACKGROUND

Cardiac allograft vasculopathy (CAV) causes late graft dysfunction and post-transplant mortality. Currently, the effects of different donor-specific antibodies (DSA) on the severity of CAV remain unclear.

METHOD

We evaluated 526 adult heart transplant recipients at a single center between January 2010 and August 2015. Subjects were divided into those with DSA (n = 142) and those without DSA (n = 384, control). The DSA group was stratified into persistent DSA (n = 34), transient DSA (n = 105), 1:8 dilution DSA (n = 45), complement-binding (C1q) DSA (n = 36), Class I DSA (n = 37), and Class II DSA (n = 105). The primary outcome was the incidence of moderate-to-severe CAV (CAV 2/3) at 5-year follow-up.

RESULTS

Subjects with persistent DSA, 1:8 dilution DSA, and C1q DSA had higher incidence of CAV 2/3 compared the control group (17.6%, 13.3%, and 16.7% vs. 3.1%, respectively; P≤ .001). The incidence of CAV 2/3 between subjects with transient DSA and the control group was similar (2.8% vs. 3.1%; P = .888). Subjects with Class II DSA also had higher incidence of CAV 2/3 (7.6% vs. 3.1%; P = .039).

CONCLUSION

DSA that are persistent, 1:8 dilution positive, C1q positive, and Class II are associated with more severe grades of CAV. These DSA characteristics may prognosticate disease and warrant consideration for treatment.

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.

Ventricular assist device bridging with gender-mismatch increases rejection and decreases survival following a heart transplant

OBJECTIVES

Survival is poor following an orthotopic heart transplant with gender-mismatched donors and recipients. Patients bridged to an orthotopic heart transplant with a ventricular assist device (VAD) frequently become sensitized. We hypothesized that the combination of VAD bridging and gender-mismatch may result in greater rejection and poorer survival.

METHODS

Data were obtained from the United Network of Organ Sharing database. Patients were divided into 4 groups: (i) VAD recipients who received a heart from a gender-matched donor (VAD-M); (ii) VAD recipients who received a heart from a gender-mismatched donor (VAD-MM); (iii) noVAD recipients who received a heart from a gender-matched donor (noVAD-M); and (iv) noVAD recipients who received a heart from a gender-mismatched donor (noVAD-MM). Rejection episodes within 1-year post-transplant and transplant survival were compared in VAD-M versus VAD-MM and noVAD-M versus noVAD-MM groups, respectively.

RESULTS

Between January 2000 and June 2017, of 33 401 adult patients who underwent heart transplants, 8648, 2441, 12 761 and 4992 patients were identified as VAD-M, VAD-MM, noVAD-M and noVAD-MM, respectively. Rejection within 1-year post-transplant occurred in 23.3% and 27.3% of the VAD-M and VAD-MM groups, respectively (P < 0.01) and in 21.8% and 23.6% of the noVAD-M and noVAD-MM groups (P = 0.02), respectively. In an adjusted survival analysis, the VAD-MM group showed significantly worse survival than the VAD-M group (P < 0.01), whereas there was no significant difference between the noVAD-M and noVAD-MM groups (P = 0.21).

CONCLUSIONS

Our results indicated that the combination of VAD bridging and gender-mismatch caused greater rejection and worse survival following a transplant. Further study is necessary to prove comparable post-transplant survival of gender-matched or -mismatched recipients without VAD bridging.

Donor-derived cell-free DNA is associated with cardiac allograft vasculopathy

BACKGROUND

The role of donor-derived cell-free DNA (dd-cfDNA) in screening for cardiac allograft vasculopathy (CAV) is unknown. We hypothesized that dd-cfDNA correlates with CAV, markers of inflammation, and angiogenesis in stable heart transplant (HT) recipients.

METHODS

Sixty-five HT recipients ≥2 years post-transplant, without recent rejection, were stratified by high (≥0.12%) versus low levels (<0.12%) of dd-cfDNA. A targeted amplification, next-generation sequencing assay (AlloSure^® ; CareDx, Inc.) was used to detect dd-cfDNA. Peripheral blood inflammatory and angiogenesis markers were assessed using a multiplex immunoassay system (Bioplex^® ).

RESULTS

Of 65 patients, 58 patients had a known CAV status and were included. Thirty had high levels of dd-cfDNA (≥0.12%), and 28 had low levels (<0.12%). CAV was present in 63% of patients with high dd-cfDNA vs. 35% with low dd-cfDNA (p = .047). Donor-specific antibodies were present in 25% of patients with high dd-cfDNA vs. 3.8% in those with low dd-cfDNA (p = .03). There were no differences in rejection episodes, inflammatory, or angiogenesis markers. Importantly, dd-cfDNA levels were not different when stratified by time post-transplant.

CONCLUSIONS

Higher dd-cfDNA levels were associated with CAV in stable chronic HT recipients. Further studies are warranted to investigate a possible association between dd-cfDNA levels and CAV severity and whether dd-cfDNA can predict CAV progression.

A mortality risk score for heart transplants after contemporary ventricular assist device bridging

BACKGROUND

We sought to derive a risk score for 1-year mortality following orthotopic heart transplantation (OHT) in patients bridged with a contemporary centrifugal left ventricular assist device (LVAD).

METHODS

Adult patients (≥18 years) in the United Network for Organ Sharing database undergoing OHT between 2010 and 2019 who were bridged with a HeartWare or HeartMate III device were included. Derivation and validation cohorts were randomly assigned with a 2:1 ratio. Threshold analysis and multivariable logistic regression were utilized to obtain adjusted odds ratios for 1-year post-OHT mortality. A risk score was generated using these adjusted odds ratios in the derivation cohort and the predictive performance of the composite index was evaluated in the validation set.

RESULTS

A total of 3434 patients were identified. In the derivation cohort, the mean age was 53.5 ± 12.1 years and 1758 (76.8%) were male; 1789 (78.1%) were bridged with a HeartWare device. Multivariable logistic regression revealed that recipient age ≥50 years, bilirubin level ≥2.4 mg/dl, ischemic time ≥4 h, and preoperative hemodialysis predicted 1-year post-transplant mortality. Stratification into risk groups in the validation cohort revealed significant differences in postoperative renal failure, stroke, and short-term mortality. One-year post-transplant mortality was 5%, 6.7%, and 14.8% in the low-, moderate-, and high-risk categories, respectively (p < .001).

CONCLUSIONS

Among patients bridged to OHT with newer generation centrifugal LVADs, older age, increasing bilirubin, longer ischemic time, and pre-OHT dialysis independently predicted post-transplant mortality. The composite risk score based on these factors may assist in patient selection and prognostication in those supported with contemporary LVADs.

Pig-to-human heart transplantation: Who goes first?

Cardiac xenotransplantation has recently taken an important step towards clinical reality. In anticipation of the "first-in-human" heart xenotransplantation trial, we propose a set of patient characteristics that define potential candidates. Our premise is that, to be ethically justified, the risks posed by current state-of-the-art options must outweigh the anticipated risks of a pioneering xenotransplant procedure. Suitable candidates include patients who are at high immunologic risk because of sensitization to alloantigens, including those who have exhibited early onset or accelerated cardiac allograft vasculopathy. In addition, patients should be considered (1) for whom mechanical circulatory support would be prohibitively risky due to a hypercoagulable state, a contraindication to anticoagulation, or restrictive physiology; (2) with severe biventricular dysfunction predicting unsuccessful univentricular left heart support; and (3) adults with complex congenital heart disease. In conclusion, because the published preclinical benchmark for clinical translation of heart xenotransplantation appears within reach, carefully and deliberately defining appropriate trial participants is timely as the basis for ethical clinical trial design.

Cardiac allograft rejection in the current era of continuous flow left ventricular assist devices

OBJECTIVE

Left ventricular assist device (LVAD) implantation has been shown to increase allosensitization before orthotopic heart transplantation, but the influence of LVAD support on posttransplant rejection is controversial. This study examines the postoperative incidence of acute cellular rejection (ACR) in patients bridged with continuous flow LVAD (CF-LVAD) relative to primary transplant (Primary Tx).

METHODS

All patients who underwent orthotopic heart transplantation at our institution between July 2006 and March 2019 were retrospectively reviewed (n = 395). Patients were classified into Primary Tx (n = 145) and CF-LVAD (n = 207) groups. Propensity score matching on 13 covariates implemented a 0.1 caliper logistic model with nearest neighbor 1:1 matching. Development of moderate to severe (ie, 2R/3R) rejection was evaluated using a competing risks model. Potential predictors of 2R/3R ACR were evaluated using Fine-Gray regression on the marginal subdistribution hazard.

RESULTS

Propensity score matching yielded 122 patients in each group (n = 244). At 12 and 24 months, the cumulative incidence of 2R/3R ACR was 17% and 23% for the CF-LVAD group and 26% and 31%, respectively, for the Primary Tx group (P = .170). CF-LVAD was not predictive of 2R/3R rejection on multivariable Fine-Gray regression (subdistribution hazard ratio, 0.73; 95% confidence interval, 0.40-1.33; P = .301). There was no difference in the 5-year incidence of antibody mediated rejection (10% [n = 12] vs 9% [n = 11]; P = .827).

CONCLUSIONS

After adjusting for covariates, CF-LVAD was not associated with an increased risk of moderate to severe ACR during the 24 months after cardiac transplantation. Further investigation is warranted with larger cohorts, but CF-LVAD may have minimal influence on posttransplant ACR.

Effects of implanting a long-term left ventricle assist device on post-transplant outcomes

BACKGROUND

An increasing number of patients are receiving left ventricle assist devices as a bridge to heart transplantation. The aim of this study was to determine the difference between patients who received transplants from a left ventricle assist device and those who underwent heart transplantation without a prior left ventricle assist device implantation.

MATERIAL AND METHODS

The study included patients who underwent heart transplantation in our institute between January 2010 and November 2018. The following clinical variables were evaluated: donor characteristics, patient's pre-transplant demographical data, post-transplant data, and patient survival. Cardiac allograft vasculopathy progression was prospectively examined (after 1 month and 12 months after heart transplantation) by coronary optical coherence tomography. We were interested in the difference in 1- and 5-year survival between the left ventricle assist device and non-left ventricle assist device groups.

RESULTS

A total of 248 patients were identified; out of them, 48 patients received a left ventricle assist device before heart transplantation, whereas 200 had transplants with no prior left ventricle assist device implantation. There were no significant differences in any donor characteristics. The mean duration of cardiopulmonary bypass time in the non-left ventricle assist device group was 156 versus 175 min in the left ventricle assist device group (p = 0.009), blood loss was 650 versus 1045 mL (p < 0.001), the need to implant an extracorporeal membrane oxygenation was 10% versus 23% (p = 0.02). There was no difference in cardiac allograft vasculopathy progression between the groups 1 year after heart transplantation (p = 0.528). The 1- and 5-year survival, according to Kaplan-Meier, was 80% and 70% in the left ventricle assist device group, compared to 80% and 73%, respectively, in the non-left ventricle assist device group (Log-rank test: p = 0.945).

CONCLUSION

Our results indicate that patients undergoing heart transplantation from left ventricle assist devices suffer significantly more from intraoperative and post-operative complications; however, only insignificant cardiac allograft vasculopathy progression and survival differences between the two groups were observed.

Sensitization in Heart Transplantation: Emerging Knowledge: A Scientific Statement From the American Heart Association

Sensitization, defined as the presence of circulating antibodies, presents challenges for heart transplant recipients and physicians. When present, sensitization can limit a transplantation candidate’s access to organs, prolong wait time, and, in some cases, exclude the candidate from heart transplantation altogether. The management of sensitization is not yet standardized, and current therapies have not yielded consistent results. Although current strategies involve antibody suppression and removal with intravenous immunoglobulin, plasmapheresis, and antibody therapy, newer strategies with more specific targets are being investigated.

The management of antibodies in heart transplantation: An ISHLT consensus document

Despite the successes from refined peri-operative management techniques and immunosuppressive therapies, antibodies remain a serious cause of morbidity and mortality for patients both before and after heart transplantation. Patients awaiting transplant who possess antibodies against human leukocyte antigen are disadvantaged by having to wait longer to receive an organ from a suitably matched donor. The number of pre-sensitized patients has been increasing, a trend that is likely due to the increased use of mechanical circulatory support devices. Even patients who are not pre-sensitized can go on to produce donor-specific antibodies after transplant, which are associated with worse outcomes. The difficulty in managing antibodies is uncertainty over which antibodies are of clinical relevance, which patients to treat, and which treatments are most effective and safe. There is a distinct lack of data from prospective trials. An international consensus conference was organized and attended by 103 participants from 75 centers to debate contentious issues, determine the best practices, and formulate ideas for future research on antibodies. Prominent experts presented state-of-the-art talks on antibodies, which were followed by group discussions, and then, finally, a reconvened session to establish consensus where possible. Herein we address the discussion, consensus points, and research ideas.

Selection of Patients for Initial Clinical Trials of Solid Organ Xenotransplantation

Several groups have reported extended survival of genetically engineered pig organs in nonhuman primates, varying from almost 10 months for life-supporting kidney grafts and more than 2 years for non-life-supporting heart grafts to less than 1 month for life-supporting liver and lung grafts. We have attempted to define groups of patients who may not have an option to wait for an allograft. These include kidney, heart, and lung candidates who are highly-allosensitized. In addition, some kidney candidates (who have previously lost at least 2 allografts from rapid recurrence of native kidney disease) have a high risk of further recurrence and will not be offered a repeat allotransplant. Patients with complex congenital heart disease, who may have undergone previous palliative surgical procedures, may be unsuitable for ventricular assist device implantation. Patients dying of fulminant hepatic failure, for whom no alternative therapy is available, may be candidates for a pig liver, even if only as a bridge until an allograft becomes available. When the results of pig organ xenotransplantation in nonhuman primates suggest a realistic potential for success of a pilot clinical trial, highly selected patients should be offered participation.

Antibody-mediated rejection in the cardiac allograft: diagnosis, treatment and future considerations

PURPOSE OF REVIEW

This review summarizes the latest publications dealing with antibody-mediated rejection (AMR) and defines areas of controversy and future steps that may improve the outcome for patients with this virulent form of rejection.

RECENT FINDINGS

Recent progress includes publication of standardized pathologic criteria for acute AMR by the International Society for Heart and Lung Transplantation (ISHLT) and guidelines for treatment of acute AMR by the American Heart Association, endorsed by ISHLT as well. Recently published review articles emphasize the important role of innate immune mechanisms, clarify the role of viral infection and provide insights into vascular biology and the role of innate effector populations, macrophages and dendritic cells.

SUMMARY

Strategies for future studies are discussed in the context of these new findings and similar efforts undertaken by renal and liver allograft investigators.

Ventricular assist device elicits serum natural IgG that correlates with the development of primary graft dysfunction following heart transplantation

BACKGROUND

Pre-transplant sensitization is a limiting factor in solid-organ transplantation. In heart transplants, ventricular assist device (VAD) implantation has been associated with sensitization to human leukocyte antigens (HLA). The effect of VAD on non-HLA antibodies is unclear. We have previously shown that polyreactive natural antibodies (Nabs) contribute to pre-sensitization in kidney allograft recipients. Here we assessed generation of Nabs after VAD implantation in pre-transplant sera and examined their contribution to cardiac allograft outcome.

METHODS

IgM and IgG Nabs were tested in pre-transplant serum samples collected from 206 orthotopic heart transplant recipients, including 128 patients with VAD (VAD patients) and 78 patients without VAD (no-VAD patients). Nabs were assessed by testing serum reactivity to apoptotic cells by flow cytometry and to the generic oxidized epitope, malondialdehyde, by enzyme-linked immunosorbent assay.

RESULTS

No difference was observed in serum levels of IgM Nabs between VAD and no-VAD patients. However, serum IgG Nabs levels were significantly increased in VAD compared with no-VAD patients. This increase was likely due to the presence of the VAD, as revealed by lower serum IgG Nabs levels before implantation. Elevated pre-transplant IgG Nabs level was associated with development of primary graft dysfunction (PGD).

CONCLUSIONS

Our study demonstrates that VAD support elicits IgG Nabs reactive to apoptotic cells and oxidized epitopes. These findings further support broad and non-specific B-cell activation by VAD, resulting in IgG sensitization. Moreover, the association of serum IgG Nabs levels with development of PGD suggests a possible role for these antibodies in the inflammatory reaction accompanying this complication.