Desensitization in heart transplant recipients: Who, when, and how

Highly sensitized patients listed for heart after liver transplantation with or without domino

For patients with end-stage heart disease and borderline hemodynamics, high human leukocyte antigen allosensitization presents a barrier to heart transplantation in a timely manner. Conventional desensitization protocols are inadequate in this context due to time constraints and for the most highly reactive immunologically. We previously reported performing heart after liver transplant with domino liver transplant on a single patient without liver disease. We describe this patient's course to date as well as 4 subsequent patients listed for this novel therapy. This experience demonstrates that the liver effectively confers immunoprotection to the heart for patients with high-titer, preformed antibodies. This strategy may provide some measure of equity for demographic groups previously disadvantaged for heart transplantation due to allosensitization.

Heart Transplant Rejection: From the Endomyocardial Biopsy to Gene Expression Profiling

Heart transplant prolongs life for patients with end-stage heart failure but rejection remains a complication that reduces long-term survival. The aim is to provide a comprehensive overview of the current status in HT rejection. EMB is an invasive diagnostic tool, consisting in the sampling of a fragment of myocardial tissue from the right ventricular septum using fluoroscopic guidance. This tissue can later be subjected to histopathological, immunohistochemical or molecular analysis, providing valuable information for cardiac allograft rejection, but this procedure is not without complications. To increase the accuracy of the rejection diagnosis, EMB requires a systematic evaluation of endocardium, myocardium, interstitium and intramural vessels. There are three types of rejection: hyperacute, acute or chronic, diagnosed by the histopathological evaluation of EMB as well as by new diagnostic methods such as DSA, ddcfDNA and gene expression profiling, the last having a high negative predictive value. More than 50 years after the introduction of EMB in medical practice, it still remains the "gold standard" in monitoring rejection in HT recipients but other new, less invasive diagnostic methods reduce the number of EMBs required.

Heart transplantation: focus on donor recovery strategies, left ventricular assist devices, and novel therapies

Heart transplantation is advocated in selected patients with advanced heart failure in the absence of contraindications. Principal challenges in heart transplantation centre around an insufficient and underutilized donor organ pool, the need to individualize titration of immunosuppressive therapy, and to minimize late complications such as cardiac allograft vasculopathy, malignancy, and renal dysfunction. Advances have served to increase the organ donor pool by advocating the use of donors with underlying hepatitis C virus infection and by expanding the donor source to use hearts donated after circulatory death. New techniques to preserve the donor heart over prolonged ischaemic times, and enabling longer transport times in a safe manner, have been introduced. Mechanical circulatory support as a bridge to transplantation has allowed patients with advanced heart failure to avoid progressive deterioration in hepato-renal function while awaiting an optimal donor organ match. The management of the heart transplantation recipient remains a challenge despite advances in immunosuppression, which provide early gains in rejection avoidance but are associated with infections and late-outcome challenges. In this article, we review contemporary advances and challenges in this field to focus on donor recovery strategies, left ventricular assist devices, and immunosuppressive monitoring therapies with the potential to enhance outcomes. We also describe opportunities for future discovery to include a renewed focus on long-term survival, which continues to be an area that is under-studied and poorly characterized, non-human sources of organs for transplantation including xenotransplantation as well as chimeric transplantation, and technology competitive to human heart transplantation, such as tissue engineering.

Post-transplantation outcomes of sensitized patients receiving durable mechanical circulatory support

BACKGROUND

Sensitization, defined as the presence of circulating antibodies, presents challenges, particularly in patients undergoing heart transplantation (HTx) bridged with durable mechanical circulatory support (MCS). We aimed to investigate the post-transplantation outcomes of sensitized MCS patients.

METHODS

Among 889 consecutively enrolled heart transplant (HTx) recipients between 2010 and 2018, 86 (9.7%) sensitized MCS patients (Group A) were compared with sensitized non-MCS patients (Group B, n = 189), non-sensitized MCS patients (Group C, n = 162), and non-sensitized non-MCS patients (Group D, n = 452) regarding post-HTx outcomes, including the incidence of primary graft dysfunction (PGD), 1-year survival, and 1-year freedom from antibody-mediated rejection (AMR).

RESULTS

Sensitized MCS patients (Group A) showed comparable rates of PGD, 1-year survival, and 1-year freedom from AMR with Groups C and D. However, Group A showed significantly higher rates of 1-year freedom from AMR (95.3% vs 85.7%, p = 0.02) and an earlier decline in panel-reactive antibody (PRA) levels (p < 0.01) than sensitized non-MCS patients (Group B). Desensitization therapy effectively reduced the levels of PRA in both Groups A and B. When Group A was further divided according to the presence of preformed donor-specific antibodies (DSA), patients with preformed DSA showed significantly lower rates of 1-year freedom from AMR than those without (84.2% vs 98.5%, p = 0.01).

CONCLUSIONS

Sensitized MCS patients showed significantly lower rates of AMR and an earlier decline in PRA levels following HTx than sensitized non-MCS patients. Removal of MCS at the time of transplantation might underlie these observations.

HLA Desensitization in Solid Organ Transplantation: Anti-CD38 to Across the Immunological Barriers

The presence of anti-human leucocyte antigen (HLA) antibodies in the potential solid organ transplant recipient's blood is one of the main barriers to access to a transplantation. The HLA sensitization is associated with longer waitlist time, antibody mediated rejection and transplant lost leading to increased recipient's morbidity and mortality. However, solid organ transplantation across the HLA immunological barriers have been reported in recipients who were highly sensitized to HLA using desensitization protocols. These desensitization regimens are focused on the reduction of circulating HLA antibodies. Despite those strategies improve rates of transplantation, it remains several limitations including persistent high rejection rate and worse long-term outcomes when compare with non-sensitized recipient population. Currently, interest is growing in the development of new desensitization approaches which, beyond targeting antibodies, would be based on the modulation of alloimmune pathways. Plasma cells appears as an interesting target given their critical role in antibody production. In the last decade, CD38-targeting immunotherapies, such as daratumumab, have been recognized as a key component in the treatment of myeloma by inducing an important plasma cell depletion. This review focuses on an emerging concept based on targeting CD38 to desensitize in the field of transplantation.

Heart transplantation candidacy

PURPOSE OF REVIEW

Timely referral of eligible candidates for consideration of advanced therapies, such as a heart transplantation or mechanical circulatory support is essential. The characteristics of heart transplantation candidates have changed significantly over the years, leading to a more complex evaluation process. The present review summarizes recent advances in the evaluation process for heart transplantation eligibility.

RECENT FINDINGS

The heart transplantation allocation policy was recently reviewed in the USA in an effort to reduce waitlist mortality and to ensure fair geographic allocation of organs to the sickest patients. Moreover, patients with chronic infectious diseases, as well as malignancies, are being currently considered acceptable candidates for transplantation. Listing practices for heart transplantation vary between programmes, with a greater willingness to consider high-risk candidates at higher-volume centres.

SUMMARY

The ultimate decision to place high-risk candidates on the heart transplantation waitlist should be based on a combination of quantitative and qualitative data analysis informed by clinical judgement, and the chronic shortage of organ donors makes this process an important ethical concern for any society. Future guidelines should discuss approaches to achieve fair organ allocation while preserving improved outcomes after transplantation.