Cyclosporine heart transplantation

Microcirculatory Disease in Patients after Heart Transplantation

Although the treatment and prognosis of patients after heart transplantation have significantly improved, late graft dysfunction remains a critical problem. Two main subtypes of late graft dysfunction are currently described: acute allograft rejection and cardiac allograft vasculopathy, and microvascular dysfunction appears to be the first stage of both. Studies revealed that coronary microcirculation dysfunction, assessed by invasive methods in the early post-transplant period, correlates with a higher risk of late graft dysfunction and death during long-term follow-up. The index of microcirculatory resistance, measured early after heart transplantation, might identify the patients at higher risk of acute cellular rejection and major adverse cardiovascular events. It may also allow optimization and enhancement of post-transplantation management. Moreover, cardiac allograft vasculopathy is an independent prognostic factor for transplant rejection and survival rate. The studies showed that the index of microcirculatory resistance correlates with anatomic changes and reflects the deteriorating physiology of the epicardial arteries. In conclusion, invasive assessment of the coronary microcirculation, including the measurement of the microcirculatory resistance index, is a promising approach to predict graft dysfunction, especially the acute allograft rejection subtype, during the first year after heart transplantation. However, further advanced studies are needed to fully grasp the importance of microcirculatory dysfunction in patients after heart transplantation.

Heart Transplantation: A Bibliometric Review From 1990-2021

BACKGROUND

As the rapidly aging population and the rising incidence of end-stage heart failure (HF), extensive research has been conducted on heart transplantation (HTx). Bibliometrics harbors the function for describing the relationships of knowledge structures in different research fields and predicting the growth trend .

METHODS

The publications were searched and filtered based on the WOS core database. The target literature was visualized and analyzed by CiteSpace or VOSviewer .

RESULTS

In total, 19,998 published papers were obtained. There is a wave-like growth in HTx development. Most advanced research results are concentrated in a few developed countries, while the interactions with developing countries are still in infancy. The United States occupies a strong dominant position among active countries on HTx. Early research hotpots mostly focused on primary disease, survival risk factors, and complications. In recent years, the research frontiers have shifted steadily to clinical evaluation of immunosuppressants and diagnosis of acute rejection, cardiac re-injury with COVID-19, innovations in ventricular assist devices(VAD), and donation allocation strategies. The research directions of HTx are gradually shifting from observational studies to intervention research.

A Comprehensive Review of Calcineurin Inhibitors Used for Immunosuppression in Cardiac Transplantation

Calcineurin inhibitors (CNIs) have been the foundation of immunosuppression in solid organ transplantation since the 1980s. Cyclosporine A (CSA), the first in class, was identified as the metabolite of the soil fungus Tolypocladium inflatum Gams as part of a larger program of screening for naturally occurring fungal metabolites with biologic activity in the 1970s. Significant immunosuppressive effects were discovered and consequently CSA was trialed as an immunosuppressant in renal transplantation. This initial success led to its widespread study and adoption in solid organ transplantation. This novel agent yielded significant improvements in both 1 year and longer-term allograft and patient survival. Subsequently, a similar and more potent CNI, tacrolimus was developed. Today, it is the principal CNI used for prevention of allograft rejection. Like all other immunosuppressives, the benefits of CNIs are counterbalanced by side effects and complications resulting from drug toxicity. This chapter comprehensively reviews the clinical use of CNIs in cardiac transplantation.

Immunosuppression following heart transplantation: prospects and challenges

Immunosuppression after heart transplantation has significantly reduced the incidence of cellular rejection and improved patient outcomes with the routine use of calcineurin inhibitors. Antimetabolites and proliferation signal inhibitors add to the improvement in patient outcomes, particularly with respect to the reduced burden of cardiac allograft vasculopathy. Patients with antibody sensitization are potentially at higher risk of postoperative complications. Sensitized patients are undergoing heart transplantation with increased frequency, in part due to the emergence of ventricular assist device use as a bridge to heart transplantation. Despite improvements in immunosuppressive therapies, many challenges face physicians and patients, which will further refine and improve care of the post-heart transplant patient.

Thoracic organ transplantation: laboratory methods

Although great progress has been achieved in thoracic organ transplantation through the development of effective immunosuppression, there is still significant risk of rejection during the early post-transplant period, creating a need for routine monitoring for both acute antibody and cellular mediated rejection. The currently available multiplexed, microbead assays utilizing solubilized HLA antigens afford the capability of sensitive detection and identification of HLA and non-HLA specific antibodies. These assays are being used to assess the relative strength of donor specific antibodies; to permit performance of virtual crossmatches which can reduce the waiting time to transplantation; to monitor antibody levels during desensitization; and for heart transplants to monitor antibodies post-transplant. For cell mediated immune responses, the recent development of gene expression profiling has allowed noninvasive monitoring of heart transplant recipients yielding predictive values for acute cellular rejection. T cell immune monitoring in heart and lung transplant recipients has allowed individual tailoring of immunosuppression, particularly to minimize risk of infection. While the current antibody and cellular laboratory techniques have enhanced the ability to manage thoracic organ transplant recipients, future developments from improved understanding of microchimerism and graft tolerance may allow more refined allograft monitoring techniques.

Immunosuppression for heart transplantation: where are we now?

The success of cardiac transplantation is largely attributable to the development of effective immunosuppressive regimens. The introduction of calcineurin inhibitors was pivotal in reducing the frequency of acute rejection and improving early survival. Newer agents, including mycophenolate mofetil (MMF) and proliferation-signal inhibitors, have shown promise in further reducing acute-rejection rates and, notably, reducing the frequency of cardiac allograft vasculopathy, which limits long-term graft survival. The introduction of first-year intravascular ultrasonography results as a surrogate marker for outcome after cardiac transplantation has helped assessment of the efficacy of immunosuppressive medications. Proliferation-signal inhibitors and MMF were shown by this imaging method to reduce cardiac allograft vasculopathy. The combination of these drugs, in tandem with the weaning of patients off calcineurin inhibitors, has been shown to reverse calcineurin-inhibitor-related nephrotoxic effects. A randomized trial that compared three of the more common immunosuppressive regimens suggested that tacrolimus and MMF are associated with a reduction in the frequency of rejection episodes that require treatment and have the fewest adverse effects. Finally, the use of statins has brought added benefit to immunosuppressive regimens by improving outcomes after cardiac transplantation, reportedly because of an immunomodulatory property. Promising newer immunosuppressive agents await clinical trials. This review presents an overview of the emerging data on immunosuppressive therapy for cardiac transplantation.

Effects of Cyclosporin A on Neurological Outcome and Serum Biomarkers in the Same Setting of Spinal Cord Ischemia Model

Spinal cord ischemic injury is one of the feared complications during aortic cross-clamping. The aim of this study was to investigate whether cyclosporin A (CsA) has a protective effect on spinal cord during ischemia in a rabbit model. A total of 22 New Zealand white rabbits were studied in three groups. One of the groups served as a sham group (n=7), in which only laparatomy was performed and closed. One group served as a control group (n=7), in which rabbits had their abdominal aortas cross-clamped for 40 min following median laparatomy. The last group was the CsA group (n=8), in which rabbits underwent the same procedure as the control group as well as CsA infusion at 20 mg/(kg . hr) over 60 min starting with aortic cross-clamping and continuing in the first 20 min of reperfusion. Neurological outcome of rabbits was evaluated according to Johnson's scale at postoperative hours 24 and 48 in all groups, and then they were killed. Their spinal cords were harvested, and segments corresponding to L4-L6 were prepared for pathological examination. Serum neuron-specific enolase (NSE) and nitric oxide (NO) levels were measured prior to and following aortic occlusion, and comparisons were made. Physiological data were similar in all groups. Rabbits in the sham group did not have any neurological deficit. However, all rabbits in the control group showed severe neurological deficits, including total paraplegia in five. According to Johnson's scale, neurological status of the rabbits at postoperative hour 48 was better in the CsA group compared to controls (p<0.01). Pathological examination of spinal cord specimens revealed a higher viability index in the CsA group compared to controls (p<0.01). Serum NSE and NO levels were lower in CsA-treated animals compared to controls. Our results demonstrate that CsA, when administered during ischemia and in the early period of reperfusion, may reduce neuronal damage in the spinal cord in a rabbit model of transient spinal cord ischemia.

Use of cyclosporine in thoracic transplantation

The use of cyclosporine (CyA) in clinical thoracic transplantation has markedly improved the survival and quality of life of patients in the past 2 decades. In the mid-1990s a significant advance in formulation design took place with the introduction of Neoral. This new microemulsion formulation of CyA demonstrates reduced intersubject and intrasubject variability in absorption and improved oral bioavailability compared with the oil-based CyA formulation. Moreover, C2 measurements of CyA could result in an even better method to avoid overimmunosuppression. On the other hand, generic alternatives of CyA could potentially reduce costs to transplant recipients as well as to the general community. Since the initiation of tacrolimus, mycophenolate mofetil, and rapamycin, slow but expanding variations of immunosuppressive protocols have taken place. Transplantation medicine is thus becoming an increasingly exciting and innovative field, in which CyA continues to play a central role as the core immunosuppressant of choice for the majority of patients.

Immunosuppression, diagnosis, and treatment of cardiac allograft rejection

The success of cardiac transplantation has been largely attributable to the development of effective immunosuppressive regimens. The calcineurin inhibitors were pivotal in reducing the frequency of acute rejection and improving early survival. Newer agents, including mycophenolate mofetil and proliferation signal inhibitors, show some promise in further reducing episodes of acute allograft rejection and also having a significant impact on reducing transplant vasculopathy. The role of cytolytic induction therapy remains unclear, although its use may be most appropriate in the high risk presensitized transplant recipient. While the endomyocardial biopsy remains the gold standard for the diagnosis of acute allograft rejection, its invasive nature makes the test suboptimal. The presence of biopsy 'negative' rejection has also led to an appreciation for the role of antibody-mediated rejection in cardiac allograft dysfunction. Effective noninvasive evaluation of allograft rejection remains the ultimate challenge. While imaging technologies have some utility because of their ease of use, more sophisticated techniques such as gene-expession analysis from peripheral blood may show the greatest promise. Management of established acute allograft rejection has significantly improved with our understanding of the immune mechanisms involved. Therapies may be targeted specifically at cellular or humoral components of the immune system.

Cardiac transplant experience with cyclosporine

The advent of cyclosporine 20 years ago was a major advance in the field of solid organ transplantation. Its use enabled directed immunosuppression with a consequent decrease in the incidence of graft failure, acute rejection, and systemic infection. The early oil-based preparation, however, was difficult to administer and had limited bioavailability and unpredictable pharmacokinetics. The drug also has a fairly narrow therapeutic window with major long-term side effects, which include nephrotoxicity, malignancy, hyperlipidemia, and hypertension. The introduction of a microemulsion preparation (Neoral) with improved bioavailability has been associated with lower rates of rejection and comparable tolerability, therefore allowing the use of lower doses. Traditionally cyclosporine toxicity has been minimized by monitoring trough levels. Monitoring of levels 2 hours after dosing may provide a more accurate determination of cyclosporine exposure. The next phase in cardiac transplantation immunosuppression will most likely see a significantly diminished role for cyclosporine with the introduction of newer, more potent immunosuppressive agents with more favorable side-effect profiles. These agents, which include mycophenolate mofetil, sirolimus, and everolimus, also hold the promise of having a major impact on the development of transplant vasculopathy, which up to now has been an important determinant of limiting long-term allograft survival.

Current practices: immunosuppression induction, maintenance, and rejection regimens in contemporary post-heart transplant patient treatment

Cardiac transplantation is the definitive treatment for eligible patients with end-stage cardiomyopathy. Survival rates have improved dramatically during the last 10 years, especially since the advent of cyclosporine-A. Cardiac allograft rejection, previously considered a major cause of early mortality after transplantation, is no longer the limiting factor for early survival, with the use of newer and more specific immunosuppression regimens. Very few randomized, prospective trials, including comparisons between immunosuppression regimens, have been conducted in this area. Therefore, practices vary with physician and institutional experience. Most centers use a multipronged approach to immunosuppression, targeting multiple sites in the immune cascade that lead to allograft rejection. Multiple new agents in development are reviewed. Drugs such as sirolimus and its derivative, everolimus, act on specific intracellular receptors within lymphocytes, whereas other medications such as Daclizumab (Roche Laboratories, Nutley, NJ) block the interleukin-2 receptor on the surface of activated T cells. The immune response to foreign antigens is complex, with multiple redundant levels. Immunosuppression regimens continue to seek a fine balance between overimmunosuppression and insufficient protection, which may lead to allograft rejection or loss.

Neoral use in the cardiac transplant recipient

CyA is the core immunosuppressant of choice for the majority of transplant patients. The introduction of Neoral, a new microemulsion formulation of CyA. and more recently a range of adjunctive immunosuppressants have further enhanced the efficacy and tolerability of CyA-based immunosuppression. In the first year following transplantation the major causes of morbidity and death are graft failure, acute rejection, and systemic infection. Patients with deteriorated pulmonary circulation before transplantation are at increased risk of early postoperative death. Risk factors for early acute rejection include female donor sex, young donor age, and multiple HLA-DR mismatches. The principal cause of death in the long term is graft vasculopathy which accounted for 40% of all deaths. Risk factors that have been hypothesized to play a role in the pathogenesis of graft vasculopathy include hyperlipidemia, recipient age and gender, donor age, the number of HLA AB and DR mismatches, and CMV infection. Strategies proposed to reduce the risk of graft vasculopathy include aggressive use of lipid-lowering agents, avoidance of low CyA doses, and the use of adjunctive rapamycin or RAD therapy. Rejection surveillance therefore relies on routine serial endomyocardial biopsy. Recent research suggests that a more accurate assessment of the state of the graft can be obtained by considering the results across a number of biopsy samples obtained from different parts of the heart, rather than basing clinical judgment on the worst single result obtained. New molecular markers such as granzyme A mRNA are likely to improve the power of histology to diagnose and predict rejection. Neoral pharmacokinetics give greater bioavailability and less intrapatient variability than Sandimmune. In the keynote OLN 351 study comparing Neoral with Sandimmune in de novo heart transplant recipients, fewer Neoral patients needed antilymphocyte therapy to treat rejection, fewer female patients had rejection episodes in the Neoral group, the tolerability of the two formulations was equivalent, and there was a lower incidence of infections in the Neoral group. The clinical impact of Neoral in comparison with Sandimmune in de novo heart transplant patients has been investigated in a number of additional trials, including long-term studies, which have confirmed that Neoral is associated with: Lower CyA doses than Sandimmune. Equal or greater antirejection efficacy than Sandimmune. Comparable tolerability to Sandimmune. During the administration of intravenous CyA as an induction therapy in the days immediately following transplantation, there is evidence to suggest that a 6-hour infusion given twice daily, which mimics the pharmacokinetic profile of oral dosing, may be clinically more effective than a continuous 24-hour infusion. Milligram-for-milligram dose conversion from Sandimmune to Neoral is feasible. Following conversion, a reduction in the CyA dose may be required in the majority of patients to maintain target levels. In pediatric patients, the rate of elimination of CyA is greater and bioavailability increases with increasing age. Younger patients (less than 8 years of age) may be managed more effectively with a 3-times-daily, rather than a twice-daily dosing schedule. A number of studies have compared the clinical effects of Sandimmune and Neoral in maintenance therapy for cardiac transplant patients. As with de novo patients, these studies have found the new formulation of CyA to be associated with lower rates of acute rejection, lower therapeutic doses, and comparable tolerability. Milligram-to-milligram conversion from the old to the new CyA formulation is generally well tolerated, although in a minority of patients there is a significant increase in CyA levels. These may be associated with a transient increase in side effects which resolve on dose reduction. There is a dose-sparing effect with Neoral. Routine monitoring of both CyA and serum creatinine levels are adv