Daily noninvasive rejection monitoring improves long-term survival in pediatric heart transplantation

Evolution of heart transplantation since Barnard's first

Barnard's first human heart transplantation in 1967 has paved the channel to numerous extensive researches and clinical experiences, mostly from the Stanford group, on orchestrating criteria for donor and recipient selection, immunosuppression, distant heart procurement, re-transplantation, and further global performance of the procedure until it became the gold standard therapy for end-stage heart failure, even in the face of an utterly limited organ availability. Much has happened since Barnard's first. There has been a rapid rise to 4,000-5,000 transplants per year. Previously, the number of transplants depended on the capacity of the units. Later on, it depended largely on the availability of donor organs. The widening of indications and reduction of contraindications to heart transplantations to include elderly patients >70 years, systemic diseases such as amyloidosis, has emerged. Indeed, heart transplantation has come a long way, and is considered a fruitful and stimulating episode in modern medicine. It is rather deplorable to watch that in the beginning of 1990s, the yearly number of heart transplantations began to decline-not because the operation had proved unsuccessful, but because donor hearts became scarce. It is rather poignant that although science and technology as well as increased experience accumulated over a long time have paved the way to make such an operation possible, its applicability is limited by lack of public awareness or its unwillingness to agree to organ donation. The average transplant survival is now over 10 years. Its prevalence and success, however, belies the fact that over 52 years ago, no one had ever attempted the procedure in man and that the procedure seemed destined for ignominy and failure just a year after the first transplant. Had it not been for the work of a few scientists and physicians, each who stepped on the broad shoulders of those who had come previously, the history of heart transplantation would be nothing more than a few legends and myths in dusty tomes.

Heart transplantation: the Berlin experience and perspectives

In patients with end-stage heart failure, heart transplants are now an ingrained practice, as they provide satisfying long-term results with good predictability and quality of life. The successful outcome has evolved from the development of effective immunosuppression, recognition of allograft rejection through diagnostic modalities and improvement in donor organ perfusion. Unfortunately, transplant availability is constrained by the shortage of donor organs and is therefore considered a casuistic therapy. The outcome is defined by unwanted effects of immunosuppressants, increased tumor occurrence and chronic transplant angiopathies. In the long term, patients fear primarily the occurrence of renal insufficiency and secondly osteoporosis with its skeletal complications and corresponding pain. Nevertheless, the overall quality of life is not very limited; on the contrary, patients demonstrate a surprisingly meaningful lives 10-20 years after the transplant. Their physical presentation is similar to those with varying co-morbidities. Most of the 20-year surviving patients are physically active and happy with their daily lives. Medical ambition has seen heart transplantation become reality and develop into an influential force regarding heart surgery, immunology, pharmacology, organ logistics and medical ethics. Its development has also molded our definitions of death and has driven public and health care approval of medical advances. It has provided a strong solidarity among politicians, sociologists, physicians and citizens. Problems regarding ethics continue to endure, and will forecast heart transplants as a defining, but temporary era in human medicine. The donor organ shortage has stimulated the use of resuscitated donor hearts and encouraged exploration and advancement of mechanical circulatory support systems and xenotransplantation as alternatives in the management of end-stage heart failure.

Non-invasive cardiac allograft rejection surveillance: reliability and clinical value for prevention of heart failure

Allograft rejection-related acute and chronic heart failure (HF) is a major cause of death in heart transplant recipients. Given the deleterious impact of late recognized acute rejection (AR) or non-recognized asymptomatic antibody-mediated rejection on short- and long-term allograft function improvement of AR surveillance and optimization of action strategies for confirmed AR can prevent AR-related allograft failure and delay the development of cardiac allograft vasculopathy, which is the major cause for HF after the first posttransplant year. Routine non-invasive monitoring of cardiac function can improve both detection and functional severity grading of AR. It can also be helpful in guiding the anti-AR therapy and timing of routine surveillance endomyocardial biopsies (EMBs). The combined use of EMBs with non-invasive technologies and methods, which allow detection of subclinical alterations in myocardial function (e.g., tissue Doppler imaging and speckle-tracking echocardiography), reveal alloimmune activation (e.g., screening of complement-activating donor-specific antibodies and circulating donor-derived cell-free DNA) and help in predicting the imminent risk of immune-mediated injury (e.g., gene expression profiling, screening of non-HLA antibodies, and circulating donor-derived cell-free DNA), can ensure the best possible surveillance and management of AR. This article gives an overview of the current knowledge about the reliability and clinical value of non-invasive cardiac allograft AR surveillance. Particular attention is focused on the potential usefulness of non-invasive tools and techniques for detection and functional grading of early and late ARs in asymptomatic patients. Overall, the review aimed to provide a theoretical and practical basis for those engaged in this particularly demanding up-to-date topic.

Role of paediatric assist device in bridge to transplant

Background

While heart transplantation has gained recognition as the gold standard therapy for advanced heart failure, the scarcity of donor organs has become an important concern. The evolution of surgical alternatives such as ventricular assist devices (VADs), allow for recovery of the myocardium and ensure patient survival until heart transplantation becomes possible. This report elaborates the role of VADs as a bridge to heart transplantation in infants and children (≤18 years old) with end-stage heart failure.

Methods

A retrospective review of the medical records of 201 heart transplant recipients between May 1986 and September 2014 identified 78 children [38.8%; mean age 7.2 (7.8±6.0) years old; IQR: 2.6-11.8 years] with advanced heart failure who were supported with a VAD [left VAD (LVAD) =21; biventricular VAD (BVAD) =57] as a bridge to heart transplantation. Fourteen (17.9%) patients were less than 1 year old; 15 (19.2%) children had a cardiac arrest and underwent cardiopulmonary resuscitation, with 7 of these patients also requiring extracorporeal membrane oxygenation (ECMO) support prior to implantation of a VAD. The aetiology of heart failure was primarily cardiomyopathy (dilative, restrictive from endocardial fibrosis, idiopathic or toxic-induced), reported in 56 (71.8%) patients. The VADs employed were primarily Berlin Heart EXCOR^® (n=63), HeartWare (n=13), Berlin Heart INCOR^® (n=1), and Toyobo (n=1).

Results

Mean duration of VAD support was 59 (133.37±191.57) days (range, 1-945 days; IQR: 23-133 days) before a donor heart became available. The primary complication encountered while patients were being bridged to transplant was mediastinal bleeding (7.8%). The main indication for pump exchanges was thrombus formation in the valves. There was no incidence of technical failure of the blood pump or driving system components. Skin infections around the cannulae occurred in 2.5%. Adverse neurological symptoms (thromboembolism 11.1%, cerebral haemorrhage 3.6%) that occurred did not have any permanent neurological sequelae that could be detected on clinical examination in this study. Mean duration of follow-up was 9.4 (10.3±7.6) years (IQR: 3.74-15.14 years). Cumulative survival rates of patients bridged to transplantation with VAD were 93.6%±2.8%, 84.6%±4.1%, 79.1%±4.7%, 63.8%±6.2%, 61.6%±7.1%, and 52.1%±9.3% at 30 days, 1, 5, 10, 15 and 20 years, respectively. There was no statistically significant difference (P=0.79) in survival rates of patients bridged to heart transplantation with VAD compared to those who underwent primary heart transplantation. Post-transplant survival rates stratified according to the type of VAD implanted and number of ventricles supported were not statistically different (P=0.93 and 0.73, respectively). In addition, post-transplant survival rates were not significantly different when age, gender and diagnosis were adjusted for. Furthermore, no statistically significant difference was found when post-transplant survival rates of children who had episodes of rejection were compared to those who did not have episodes of rejection.

Conclusions

The results in this series demonstrate that VADs satisfactorily support paediatric patients with advanced heart failure from a variety of aetiologies until heart transplantation. The data further suggests that patients bridged with VADs have comparable long-term post-transplant survival as those undergoing primary heart transplantation.

State of the art in paediatric heart transplantation: the Berlin experience

Enormous progress has been made in paediatric heart transplantation since the first unsuccessful effort by Kantrowitz in 1967. Early reports of children undergoing heart transplantation showed alarmingly high perioperative mortality rates of 25-60%, with the diagnosis of congenital heart disease (CHD) representing a particularly high-risk subset compared with cardiomyopathy. Many of these early failures were related to poor patient selection, suboptimal immunosuppression and technical problems. We learned a great deal from these earlier difficulties. Presently, with more refined techniques, better-defined patient selection criteria, excellent graft rejection monitoring and optimal immunosuppression, the ISHLT 2011 registry reported a 10-year survival rate of 60% for patients transplanted for end-stage CHD and >70% for those transplanted for cardiomyopathy. The technical dilemmas in complex CHD were overcome by surgical ingenuity and creativity, innovative solutions and careful surgical planning, adapting the complex recipient anatomy to the normal donor anatomy. The miniaturized Berlin Heart pulsatile ventricular assist devices in children as a bridge to transplantation have revolutionized treatment and become a significant contribution in heart-failure therapy. The intramyocardial electrogram and echocardiographic strain rate imaging have been employed as non-invasive techniques of rejection monitoring. Immunosuppressive drugs have a major impact on the development and progression of cardiac allograft vasculopathy, the main cause of cardiac allograft loss and a leading cause of mortality after the first year post-transplantation. The questions of whether a transplanted heart in a newborn grows to adult size along with the child and whether the dimensional cardiac growth allows adequate function over time have been largely answered in our previous investigations. As more transplanted children reach adulthood, concerns about their life expectancy when they have reached 10 years of life post-transplant are raised, particularly with respect to establishing partnerships and families, their ability to earn a living and the fulfilment of personal life perspectives. Some heart-transplanted patients require retransplantation to remain alive. The disparity between the demand for and supply of donor hearts makes retransplantation an ethical issue. We 'do not refuse' any patient who needs retransplantation. Mechanical circulatory support devices for long-term use are now largely available to accommodate such cases.

Novel implantable device to detect cardiac allograft rejection

BACKGROUND

Allograft rejection remains the nemesis of solid organ transplantation. Soul Mate is a novel implantable wireless data transmission system that analyzes 9 intramyocardial electrogram parameters recorded from 4 or 6 configurations of 2 or 3 epicardial leads to detect allograft rejection. This study determined the ability of the Soul Mate to detect early rejection of transplanted hearts.

METHODS AND RESULTS

Five dogs underwent heterotopic cervical heart transplantation and simultaneous implantation of the Soul Mate's Cardiac Rejection Monitoring Device. Dogs were initially immunosuppressed, but subsequent drug discontinuation allowed allograft rejection to appear. Allograft biopsies were performed at regular intervals to determine rejection grade, which was compared to a calculated rejection score determined as percent change from baseline of values for each intramyocardial electrogram. There was significant correlation between the biopsy results and the evolution of 5 parameters. The strongest correlation (r=0.939; P<0.001) was obtained using the "general median" parameter from 4 configurations, assessed 1 day before the biopsy, with a sensitivity of 85.7% and a specificity of 100% compared to the myocardial biopsy results.

CONCLUSIONS

The Soul Mate allograft rejection monitoring system accurately detected transplanted heart rejection in a canine model noninvasively with continuous sampling. This proof-of-concept study suggests that the Soul Mate could be used to more intensely and more frequently monitor cardiac allografts for rejection.

Wireless Acoustic Communication With a Miniature Pressure Sensor in the Pulmonary Artery for Disease Surveillance and Therapy of Patients With Congestive Heart Failure

OBJECTIVES

The purpose of this study was to examine the feasibility of repeated pulmonary artery (PA) pressure determinations using a newly developed acoustic wireless implanted communication system.

BACKGROUND

Congestive heart failure management strategies based on monitored intracardiac hemodynamics in patients receiving the best-available therapy may improve outcome. Although electromagnetic communication requires a large antenna for sufficient energy transfer, acoustic energy readily penetrates deep into the body, uses little energy, and uses small internal transducers for bidirectional operation.

METHODS

A miniature device was developed and implanted using right heart catheterization. The ability to obtain PA pressure from the implant using wireless acoustic communication was examined in 8 pigs and 10 patients with congestive heart failure. Macroscopic and histopathologic examinations were performed at 6 months after implantation. The accuracy of PA pressure measurement was determined by comparison with simultaneous pressures from a Millar catheter.

RESULTS

The device was successfully implanted in the PA using right heart catheterization. There were no implantation or later device-related complications. Pulmonary artery pressure tracings were repeatedly obtained from all implants. Normal reactions to intravascular implant were observed macroscopically and in histologic sections. Standard deviations of the difference between implant and Millar PA diastolic pressure were 1.45 and 1.2 mm Hg (animals and humans, respectively). Data were useful for patient management.

CONCLUSIONS

This pilot study demonstrates, for the first time, that acoustic wireless communication with a miniature implanted sensor is feasible and provides repeated PA pressure measurement. This feat makes possible multiple novel applications for monitoring and therapeutic interventions based on measurements from deeply implanted devices.

Mechanical cardiac support in the young with the Berlin Heart EXCOR pulsatile ventricular assist device: 15 years' experience

The pediatric-size pneumatically driven pulsatile extracorporeal ventricular assist device (VAD) Berlin Heart EXCOR (Berlin Heart Mediprodukt GmbH, Berlin, Germany) was introduced into clinical practice by the German Heart Institute Berlin in 1992. Until July 1, 2005, Berlin Heart EXCOR systems have been used for circulatory support in 68 children up to 18 years of age with severe circulatory failure resistant to pharmacologic therapy. These were patients suffering from cardiomyopathy, fulminant myocarditis, end-stage congenital cardiac defects, and acute heart failure following congenital heart surgery. Mean VAD support time was 35 days (range, 0 to 420 days). Forty-two patients (62%) survived to transplantation or after weaning; 37 patients (54%), including eight infants, were discharged home. These results in patients with very advanced disease have improved significantly in recent years because of technical developments and growing experience in the treatment of patients on the device, in postoperative care and optimal timing for VAD implantation. Timely implantation of the Berlin Heart EXCOR in the course of progressive heart failure now appears to be justified because the system has undergone the necessary modifications and the accumulation of clinical knowledge has made its use highly reliable and safe.

Serial signal-averaged electrocardiography in children after cardiac transplantation

In patients with myocytolysis detected in endomyocardial biopsy, there is a tendency towards a shift of ventricular electrical axes from normal to strain pattern on surface ECG. Their 12-lead signal-averaged electrocardiogram (SAECG) show a significant increase in filtered QRS duration (QRSD) compared with those with specimens without myocytolysis. Late potentials were generally found more frequently in individual SAECG leads than in the vector magnitude. An increase in filtered QRSD and the presence of late potentials compared with a baseline study emphasizes the need for endomyocardial biopsy. Consequently, no change in these parameters may preclude the indication for endomyocardial biopsy.

Echo-guided endomyocardial biopsy in heart transplant recipients

After heart transplantation the effect of immunosuppression is monitored by histopathology of endomyocardial biopsy (EMB). EMB is usually carried out under X-ray guidance. Between January 1998 and March 2003, 1,262 biopsies were collected under echo-guidance in 156 patients. The biopsy access was gained through the internal jugular vein, by the standard catheterization technique. The average time of the procedure was 17 min. Four or five specimens were obtained from each patient, with a success rate of 96%. Complications involved two episodes of partial pneumothorax in one patient, atrial flutter in another and ventricular fibrillation in three patients. Conversion from echo to X-ray guidance was indicated in 11 patients. No case of significant tricuspid regurgitation related to the EMB procedure was recorded. The echo-guided endomyocardial biopsy appears to be a prospective alternative to the conventional approach under X-ray guidance. Its duration is comparable, it eliminates X-ray exposure, enables continuous echocardiographic monitoring and can be performed at the bedside.

Heart transplantation in children after mechanical circulatory support with pulsatile pneumatic assist device

BACKGROUND

Mechanical support with a pulsatile pneumatic ventricular assist device (VAD) is a complex rescue procedure performed in children with untreatable cardiogenic shock. Its impact on early and long-term survival after subsequent heart transplantation (HTx) remains to be determined.

METHODS

We reviewed retrospectively the course of 95 children (median age, 8 years; range, 8 days-17 years; body weight, 24 kg; range, 3-110 kg) who underwent HTx. Group A, the elective-HTx group, consists of 33 children who were treated as outpatients before transplantation. Group B, the emergency-HTx group, has 44 children who were critically ill and hospitalized before transplantation but without ventricular assist devices, whereas Group C, the VAD-HTx group, consists of 18 children resuscitated and supported with pulsatile pneumatic VADs for a median time of 20 days.

RESULTS

Overall actuarial survival after cardiac transplantation was 86% at 1 month, 82% at 1 year, and 78% at 5 years, without significant differences among the 3 sub-groups. Group A had the best long-term survival rate, 88% at 1 month, 88% at 1 year, and 80% at 5 years. Group B had a survival rate of 88% at 1 month, 82% at 1 year, and 79% at 5 years. Group C had a survival rate of 72% at 1 month, 72% at 1 year, and 72% at 5 years. We found no differences in neurologic outcome, acute cardiac rejection, or transplant failure. The survival rate was significantly better in the children with cardiomyopathy compared with those with congenital heart defects (p = 0.014).

CONCLUSIONS

Bridging to HTx with a pulsatile pneumatic VAD is a safe procedure in pediatric patients. After HTx, overall survival of these children is similar to that of patients who were bridged with inotropes or who were awaiting heart transplantation electively.

Pulsatile pediatric ventricular assist devices: Current results for bridge to transplantation

While pulsatile ventricular assist devices have gained widespread use in adult patients awaiting heart transplantation, only very limited experience with these devices exists in the pediatric population. In the past mostly non-pulsatile systems such as ECMO have been used to support pediatric patients with heart failure for very limited periods of time. Only recently have miniaturized pulsatile devices became available. This article describes the technical characteristics of these devices which have been implanted at the Deutsches Herzzentrum Berlin since 1992. The Berlin Heart assist device has since been used in 34 children between the ages of 6 days and 16 years. We report our strategy in patient selection, perioperative care and subsequent heart transplantation. The current literature on mechanical circulatory support in children is reviewed. Copyright 1999 by W.B. Saunders Company

Circulatory support with pneumatic paracorporeal ventricular assist device in infants and children

BACKGROUND

Mechanical circulatory support in intractable heart failure in children has been limited to centrifugal pumps and extracorporeal membrane oxygenation: Since 1990 small adult-size pulsatile air-driven ventricular assist devices "Berlin Heart" (VAD) and, since 1992 miniaturized pediatric VAD (12, 15, 25, 30 mL pumps), have been used in our institution. Since 1994 the blood-contacting surfaces of the device system have been heparin-coated. In this report the experiences with VAD support in 28 children are presented.

METHODS

In 28 children-ages between 6 days and 16 years-the Berlin Heart VAD has been applied for periods of between 12 hours and 98 days (mean, 16.9 days) aiming at keeping the patient alive and allowing for recovery from shock sequelae until later transplantation or myocardial recovery. There were three groups. Group I: with primary intention of "bridge-to-transplantation" in various forms of cardiomyopathy (n = 13) or chronic stages of congenital heart disease (n = 5). Group II: "Rescue" in intractable heart failure early after corrective surgery for congenital heart disease (n = 4) or in early graft failure after a heart transplantation (n = 1). Group III: "Acute myocarditis" (n = 5) aiming at either myocardial recovery or transplantation. Twelve were brought to the operating room under cardiac massage and 25 had been on the respirator for more than 24 hours.

RESULTS

Twelve patients died on the system from sequelae of profound shock-multiorgan failure, sepsis, loss of peripheral circulatory resistance-or from hemorrhagic complications (n = 4) or brain death (n = 1). Thirteen patients (groups I and III) were transplanted after support periods of between 3 and 98 days with 7 long-term survivors living now up to 7.5 years (mean, 4.4 years). Three patients (groups II and III) were weaned from the system with two long-term survivors (both in group III). There were no patients in group II who survived and the "rescue" indication has been discarded for VAD since 1992. Such patients are since treated by extracorporeal membrane oxygenation (ECMO) in our institution. Out of the 8 patients placed on VAD during 1996 and 1997, 7 were successfully supported until transplantation or weaning. Thirteen patients were extubated and mobilized on the system. Whereas with the earlier systems thrombi in the blood pumps were seen in 15 instances and 2 patients suffered from thromboembolic complications, no thrombotic events occurred with the heparin-coated systems.

CONCLUSIONS

After accumulating clinical experience and several technical improvements since 1990 the use of the pediatric Berlin Heart VAD has matured into a reliable and safe system to keep patients with otherwise intractable heart failure alive until complete myocardial recovery is reached or transplantation becomes feasible. Whereas heart failure early after cardiac operation is now primarily treated by ECMO, acute myocarditis appears to be a promising precondition for complete cardiac recovery during VAD support.