Christiaan Barnard and his contributions to heart transplantation

Invasive Intracoronary Imaging of Cardiac Allograft Vasculopathy: Established Modalities and Emerging Technologies

Despite advances in the care of heart transplant recipients during the past 5 decades, cardiac allograft vasculopathy (CAV) continues to be a major barrier to long-term survival. The early diagnosis and treatment of CAV is crucial for improving long-term outcomes. Coronary angiography, the current gold standard for CAV screening, has low sensitivity for detecting early CAV. Increasingly, invasive intracoronary imaging modalities that provide a more detailed analysis of vessel anatomy and allow for plaque characterization are being used to detect CAV earlier after transplant and uncover mechanistic insights. Studies validating these emerging imaging platforms are needed before their widespread adoption.

Nerve regeneration in transplanted organs and tracer imaging studies: A review

The technique of organ transplantation is well established and after transplantation the patient might be faced with the problem of nerve regeneration of the transplanted organ. Transplanted organs are innervated by the sympathetic, parasympathetic, and visceral sensory plexuses, but there is a lack of clarity regarding the neural influences on the heart, liver and kidneys and the mechanisms of their innervation. Although there has been considerable recent work exploring the potential mechanisms of nerve regeneration in organ transplantation, there remains much that is unknown about the heterogeneity and individual variability in the reinnervation of organ transplantation. The widespread availability of radioactive nerve tracers has also made a significant contribution to organ transplantation and has helped to investigate nerve recovery after transplantation, as well as providing a direction for future organ transplantation research. In this review we focused on neural tracer imaging techniques in humans and provide some conceptual insights into theories that can effectively support our choice of radionuclide tracers. This also facilitates the development of nuclear medicine techniques and promotes the development of modern medical technologies and computer tools. We described the knowledge of neural regeneration after heart transplantation, liver transplantation and kidney transplantation and apply them to various imaging techniques to quantify the uptake of radionuclide tracers to assess the prognosis of organ transplantation. We noted that the aim of this review is both to provide clinicians and nuclear medicine researchers with theories and insights into nerve regeneration in organ transplantation and to advance imaging techniques and radiotracers as a major step forward in clinical research. Moreover, we aimed to further promote the clinical and research applications of imaging techniques and provide clinicians and research technology developers with the theory and knowledge of the nerve.

Heart Transplant and Ventricular Assist: Cardiac Surgery and Heart Failure Perspective

For nearly 60 years, there have been two surgical treatment options for individuals with severe advanced heart failure: heart transplantation or implantation of a left ventricular assist device. As these fields have advanced in parallel, improvements in surgical technique, device development, and patient selection have improved outcomes for both therapies. Development of a comprehensive approach to the management of the most severe forms of advanced heart failure requires a deep understanding of both heart transplantation and durable ventricular assistance, including recent advancements in both fields. This article will review the substantial progress in the fields of heart transplantation and mechanical left ventricular assistance, including recent changes to organ allocation prioritization and left ventricular assist device evaluation, both of which have dramatically influenced practice in these fields.

"You cannot stay in the laboratory forever"*: Taking pig kidney xenotransplantation from the laboratory to the clinic

Progress in life-supporting kidney transplantation in the genetically-engineered pig-to-nonhuman primate model has been encouraging, with pig kidneys sometimes supporting life for > 1 year. What steps need to be taken by (i) the laboratory team, and (ii) the clinical team to prepare for the first clinical trial? The major topics include (i) what currently-available genetic modifications are optimal to reduce the possibility of graft rejection, (ii) what immunosuppressive therapeutic regimen is optimal, and (iii) what steps need to be taken to minimize the risk of transfer of an infectious microorganism with the graft. We suggest that patients who are unlikely to live long enough to receive a kidney from a deceased human donor would benefit from the opportunity of a period of dialysis-free support by a pig kidney, and the experience gained would enable xenotransplantation to progress much more rapidly than if we remain in the laboratory.

Does the heart transplant have a future?

Heart failure has remained the leading cause of death globally for the last 15 years—and its prevalence will continue to rise. Fifty years ago, heart failure management was enriched by the possibility of a heart transplant. Despite impressive improvements in medical treatment for heart failure, a heart transplant remains the most effective long-lasting treatment for advanced heart failure in terms of mortality and quality of life. However, donor and recipient characteristics have changed dramatically in recent years, leading to more complex decision-making regarding organ acceptance and to more demanding operations and postoperative management. With improving pathophysiological understanding in the last decades, today’s scientific interest still focuses on basic knowledge. How to retrieve and conserve organs to minimize ischaemic injury; how best to allocate them, considering the likelihood of success (developing a heart-allocation scoring system similar to that for lung allocation); how to match donor/recipient characteristics (ABO blood-group antigen compatibility versus incompatibility); and how to avoid graft failure, rejection and secondary morbidities such as malignomas and cardiac allograft vasculopathy after the heart transplant—all these factors remain fundamental challenges in today’s transplant medicine. The use of ex vivo perfusion (e.g. via the Organ Care System^®, TransMedics, Andover, MA, USA) may play an important role in this change. Remarkably, there are huge regional divergences in current transplant practices: Whereas the number of transplants continues to rise in most Eurotransplant countries and other major transplant networks, there are some countries in which transplant numbers are static or even dropping (as in Germany). This difference results in wide variations across different countries as to how advanced heart failure is treated using mechanical circulatory-assist devices.

Association of Endothelin-1 With Accelerated Cardiac Allograft Vasculopathy and Late Mortality Following Heart Transplantation

BACKGROUND

Endothelin-1 (ET-1) has been implicated in the development of post-heart transplantation (HT) cardiac allograft vasculopathy (CAV), but has not been well studied in humans.

METHODS AND RESULTS

In 90 HT patients, plasma ET-1 was measured within 8 weeks after HT (baseline) via a competitive enzyme-linked immunosorbent assay. Three-dimensional volumetric intravascular ultrasound of the left anterior descending artery was performed at baseline and at 1 year. Accelerated CAV (lumen volume loss) was defined with the 75th percentile as a cutoff. Patients were followed beyond the first year after HT for late death or retransplantation. A receiver operating characteristic (ROC) curve demonstrated that a baseline ET-1 concentration of 1.75 pg/mL provided the best accuracy for diagnosis of accelerated CAV at 1 year (area under the ROC curve 0.69, 95% confidence interval [CI] 0.57-0.82; P = .007). In multivariate logistic regression, a higher baseline ET-1 concentration was independently associated with accelerated CAV (odds ratio [OR] 2.13, 95% CI 1.15-3.94; P = .01); this relationship persisted when ET-1 was dichotomized at 1.75 pg/mL (OR 4.88, 95% CI 1.69-14.10; P = .003). Eighteen deaths occurred during a median follow-up period of 3.99 (interquartile range 2.51-9.95) years. Treated as a continuous variable, baseline ET-1 was not associated with late mortality in multivariate Cox regression (hazard ratio [HR] 1.22, 95% CI 0.72-2.05; P = .44). However, ET-1 >1.75 pg/mL conferred a significantly lower cumulative event-free survival on Kaplan-Meier analysis (P = .047) and was independently associated with late mortality (HR 2.94, 95% CI 1.12-7.72; P = .02).

CONCLUSIONS

Elevated ET-1 early after HT is an independent predictor of accelerated CAV and late mortality, suggesting that ET-1 has durable prognostic value in the HT arena.

Christiaan Barnard-The surgeon who dared: The story of the first human-to-human heart transplant

In 2017, we celebrated the 50th anniversary of the first human heart transplant that had been carried out by the South African surgeon, Christiaan ('Chris') Barnard at Groote Schuur Hospital in Cape Town on December 3rd, 1967. The daring operation and the charismatic surgeon received immense public attention around the world. The patient's progress was covered by the world's media on an almost hourly basis. Although the patient, Mr. Louis Washansky, died after only 18 days, Barnard soon carried out a second transplant, and this patient led an active life for almost 19 months. Remarkably, Barnard's fifth and sixth patients lived for almost 13 and 24 years, respectively. Barnard subsequently introduced the operation of heterotopic heart transplantation in which the donor heart acted as an auxiliary pump, with some advantages in that early era. It took great courage to carry out the first heart transplant, and this is why Barnard is remembered as a pioneer in cardiac surgery.

Heart Transplantation Survival and Sex-Related Differences

Orthotopic heart transplantation (OHT) is the "gold standard" treatment for patients with end-stage heart failure, with approximately 5000 transplants performed each year worldwide. Heart transplantation survival rates have progressively improved at all time points, despite an increase in donor and recipient age and comorbidity and greater recipient urgency; according to the registry of the International Society of Heart and Lung Transplantation (ISHLT), the median survival of patients posttransplantation is currently 12.2 years.Long-term survival is sub-optimal, and outcomes after OHT remain constrained by the development of acute rejection and cardiac allograft vasculopathy (CAV). Moreover, donor organs are in short supply, making optimal organ utilization an ongoing priority. For these reasons, substantial interest continues to exist in identifying factors portending increased survival and improved organ utilization.

Antibody-Mediated Rejection in Solid Organ Transplant

Within a little more than a decade, the transplant of human organs for end-stage organ disease became a reality. The early barriers to successful long-term graft and patient survival were related to the inability to effectively control the immune system such that it would not attack the donor tissue but would still recognize and destroy invading organisms and cells. As immunosuppressive therapy has been refined and proper matching of donors and recipients has been improved, hyperacute rejection has become a rare occurrence and acute rejection has been markedly controlled. However, antibody-mediated rejection remains an important impediment to increased survival of transplanted organs. This article provides readers with a broad overview of the immune system, discusses mechanisms of transplant rejection, and details prevention, detection, and treatment of antibody-mediated rejection in solid organ transplant.

Christiaan Barnard

Christiaan Neethling Barnard (1922-2002) was an accomplished cardiac surgeon and researcher who made significant contributions to the development of the discipline. He performed the first human-to-human heart transplant in 1967 in Cape Town, South Africa. He was trained in cardiac surgery at the University of Minnesota under pioneer surgeons C. Walton Lillehei and Richard L. Varco. Many future distinguished cardiac surgeons, such as Shumway, Cabrol, and many others, were his contemporaries at Minnesota. Barnard was a highly talented individual, very dedicated and committed to continuous excellent work, particularly in the early stages of his career. He made great advances to heart valve surgery, complicated congenital heart defects, orthotopic heart transplantation, heterotopic heart transplantation, xenotransplantation, and cardiac hypothermic storage. Barnard was the center of attention globally for several years after the seminal first heart transplant operation. Our work reviews the life, accomplishments, and personal character of this superb heart surgeon.

Prediction of functional recovery of 60-minute warm ischemic hearts from asphyxiated canine non-heart-beating donors

BACKGROUND

Cardiac function of non-heart-beating donors (NHBDs) is uncertain due to severe myocardial damage. We developed an isolated myocardial perfusion system to resuscitate NHBD hearts and attempted to predict functional recovery of 60-minute warm ischemic hearts by analyzing systolic and diastolic functions.

METHODS

Hypoxic cardiac arrest was induced in 8 mongrel dogs without any pre-treatments. After 60-minute ischemia, intracoronary microthrombi were flushed out by retrograde blood cardiopledia with tissue-type plasminogen activator. Coronary arteries were initially perfused from the aortic root with tepid hyperkalemic blood (20 mmol/liter) at low pressure (20 mm Hg) for the first 60 minutes and then with normothermic blood for the next 60 minutes. After 120 minutes of reperfusion, pre-load was increased for ejection against an after-load of 80 mm Hg. Pressure-volume loops were recorded to obtain the end-systolic pressure-volume relationship (ESPVR) and end-diastolic pressure-volume relationship (EDPVR). Stroke volume at a given pre-load was calculated from averaged ESPVR, EDPVR and after-load identical to an averaged baseline value. The Frank-Starling relationship was obtained and cardiac status was classified according to Forrester's hemodynamic sub-set.

RESULTS

End-systolic elastance decreased significantly to about 60% of baseline and the time constant of isovolumic relaxation was prolonged significantly by about 20%. Cardiac index was decreased to about 50% and cardiac status was classified in the Forrester III or IV sub-set.

CONCLUSIONS

The extent of functional recovery of NHBD hearts is predictable by cardiac output. Although 120 minutes of recovery time may be short for 60-minute ischemic damage, this system may be feasible to predict post-transplant cardiac function before transplantation.

Alternative therapies for orthotopic heart transplantation

Heart failure has reached epidemic proportions in the United States. More than 5 million patients are treated for heart failure and approximately a half a million new patients are diagnosed with this disease each year in the United States. Recent pharmacological therapies have been used for the treatment of this patient population, but heart failure remains a major source of morbidity and mortality for patients. Orthotopic heart transplantation is a viable treatment option for heart failure patients; however, cardiac transplantation is limited by the donor availability. Limited donor organ availability has led to the development of alternative therapeutic strategies, including xenotransplantation, mechanical support devices, and cell transfer/tissue engineering protocols. This review highlights the current treatment modalities and emerging strategies for the treatment of advanced heart failure.

Heart Transplantation: The Contributions of Christiaan Barnard and the University of Cape Town/Groote Schuur Hospital

Christiaan (Chris) Neethling Barnard was born in South Africa and qualified in medicine at the University of Cape Town in 1946. Following surgical training in South Africa and the USA, Barnard established a successful open-heart surgery program at Groote Schuur Hospital and the University of Cape Town in 1958. In 1967, he led the team that performed the world's first human-to-human heart transplant. Although the first heart transplant patient survived only 18 days, four of Groote Schuur hospital's first 10 patients survived for more than one year, two living for 13 and 23 years, respectively. This relative success amid many failures worldwide did much to generate guarded optimism that heart transplantation would eventually become a viable therapeutic option, Barnard then developed the operation of heterotopic heart transplantation (the socalled "piggy-back" transplant), which had some advantages in the pre-cyclosporine era when immunosuppressive therapy was limited. His group was the first to successfully transport donor hearts using a hypothermic perfusion storage device in 1981. Several studies on the haemodynamic and metabolic sequelae of brain death were carried out in his Department's cardiovascular research laboratories at the University of Cape Town, and the concept of hormonal replacement therapy in organ donors was developed. An active heart transplant program still continues in the Chris Barnard Division of Cardiothoracic Surgery at Groote Schuur Hospital and the University of Cape Town, but the thrust of clinical activity within the Division and the research within its state-of-the-art cardiovascular research laboratories is now directed towards valvular and ischaemic heart diseases, which are common in the African population.

A History of Orthotopic Heart Transplantation

Orthotopic human heart transplantation today is performed at more than 150 U.S. centers, and the average survival is more than 10 years. Its prevalence and success, however, belies the fact that just 40 years ago, no one had ever attempted the procedure in humans and that the procedure seemed destined for failure just a year after the first transplant. This article reviews the history of orthotopic heart transplantation, beginning with ancient Greek legends and culminating in modern successes.

Heart transplantation

Heart transplantation remains the best treatment option for end-stage heart failure. For patients who are not candidates for transplantation, better medical management and surgical options in heart failure can improve both the length and quality of a patient's life. Continuing research on xenotransplantation and the total artificial heart may decrease the need for human transplantation in years to come and may allow others with severe heart failure to have a chance at living longer.