Donor Brain Death Time and Impact on Outcomes in Heart Transplantation

Donor Cardiac Troponin for Prognosis of Adverse Outcomes in Cardiac Transplantation Recipients: a Systematic Review and Meta-analysis

BACKGROUND

Cardiac troponin is a highly specific and widely available marker of myocardial injury, and elevations in cardiac transplant donors may influence donor selection. We aimed to investigate whether elevated donor troponin has a role as a prognostic biomarker in cardiac transplantation.

METHODS

In a systematic review and meta-analysis, we searched MEDLINE, Embase, and the Cochrane Library, without language restriction, from inception to December 2020. We included studies reporting the association of elevated donor troponin with recipient outcome after cardiac transplant. We generated summary odds ratios and hazard ratios for the association of elevated donor troponin with short- and long-term adverse outcomes. Methodological quality was monitored using the Quality In Prognosis Studies tool, and interstudy heterogeneity was assessed using a series of sensitivity and subgroup analyses.

RESULTS

We included 17 studies involving 15 443 patients undergoing cardiac transplantation. Elevated donor troponin was associated with increased odds of graft rejection at 1 y (odds ratio, 2.54; 95% confidence interval, 1.22-5.28). No significant prognostic relationship was found between donor troponin and primary graft failure, short- to long-term mortality, cardiac allograft vasculopathy, and pediatric graft loss.

CONCLUSIONS

Elevated donor troponin is not associated with an increased short- or long-term mortality postcardiac transplant despite increasing the risk of graft rejection at 1 y. Accordingly, an elevated donor troponin in isolation should not exclude donation.

A clinically relevant sheep model of orthotopic heart transplantation 24 h after donor brainstem death

Background

Heart transplantation (HTx) from brainstem dead (BSD) donors is the gold-standard therapy for severe/end-stage cardiac disease, but is limited by a global donor heart shortage. Consequently, innovative solutions to increase donor heart availability and utilisation are rapidly expanding. Clinically relevant preclinical models are essential for evaluating interventions for human translation, yet few exist that accurately mimic all key HTx components, incorporating injuries beginning in the donor, through to the recipient. To enable future assessment of novel perfusion technologies in our research program, we thus aimed to develop a clinically relevant sheep model of HTx following 24 h of donor BSD.

Methods

BSD donors (vs. sham neurological injury, 4/group) were hemodynamically supported and monitored for 24 h, followed by heart preservation with cold static storage. Bicaval orthotopic HTx was performed in matched recipients, who were weaned from cardiopulmonary bypass (CPB), and monitored for 6 h. Donor and recipient blood were assayed for inflammatory and cardiac injury markers, and cardiac function was assessed using echocardiography. Repeated measurements between the two different groups during the study observation period were assessed by mixed ANOVA for repeated measures.

Results

Brainstem death caused an immediate catecholaminergic hemodynamic response (mean arterial pressure, p = 0.09), systemic inflammation (IL-6 - p = 0.025, IL-8 - p = 0.002) and cardiac injury (cardiac troponin I, p = 0.048), requiring vasopressor support (vasopressor dependency index, VDI, p = 0.023), with normalisation of biomarkers and physiology over 24 h. All hearts were weaned from CPB and monitored for 6 h post-HTx, except one (sham) recipient that died 2 h post-HTx. Hemodynamic (VDI - p = 0.592, heart rate - p = 0.747) and metabolic (blood lactate, p = 0.546) parameters post-HTx were comparable between groups, despite the observed physiological perturbations that occurred during donor BSD. All p values denote interaction among groups and time in the ANOVA for repeated measures.

Conclusions

We have successfully developed an ovine HTx model following 24 h of donor BSD. After 6 h of critical care management post-HTx, there were no differences between groups, despite evident hemodynamic perturbations, systemic inflammation, and cardiac injury observed during donor BSD. This preclinical model provides a platform for critical assessment of injury development pre- and post-HTx, and novel therapeutic evaluation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40635-021-00425-4.

In Situ Pre-Treatment of Vascularized Composite Allografts With a Targeted Complement Inhibitor Protects Against Brain Death and Ischemia Reperfusion Induced Injuries

Introduction

Donor brain death (BD) is an unavoidable component of vascularized composite allograft (VCA) transplantation and a key contributor to ischemia-reperfusion injury (IRI). Complement is activated and deposited within solid organ grafts as a consequence of BD and has been shown to exacerbate IRI, although the role of BD and complement in VCA and the role it plays in IRI and VCA rejection has not been studied.

Methods

BD was induced in Balb/c donors, and the VCA perfused prior to graft procurement with UW solution supplemented with or without CR2-Crry, a C3 convertase complement inhibitor that binds at sites of complement activation, such as that induced on the endothelium by induction of BD. Following perfusion, donor VCAs were cold stored for 6 hours before transplantation into C57BL/6 recipients. Donor VCAs from living donors (LD) were also procured and stored. Analyses included CR2-Crry graft binding, complement activation, toxicity, injury/inflammation, graft gene expression and survival.

Results

Compared to LD VCAs, BD donor VCAs had exacerbated IRI and rejected earlier. Following pretransplant in-situ perfusion of the donor graft, CR2-Crry bound within the graft and was retained post-transplantation. CR2-Crry treatment significantly reduced complement deposition, inflammation and IRI as compared to vehicle-treated BD donors. Treatment of BD donor VCAs with CR2-Crry led to an injury profile not dissimilar to that seen in recipients of LD VCAs.

Conclusion

Pre-coating a VCA with CR2-Crry in a clinically relevant treatment paradigm provides localized, and therefore minimally immunosuppressive, protection from the complement-mediated effects of BD induced exacerbated IRI.

Heart Transplantation From Brain Dead Donors: A Systematic Review of Animal Models

Despite advances in mechanical circulatory devices and pharmacologic therapies, heart transplantation (HTx) is the definitive and most effective therapy for an important proportion of qualifying patients with end-stage heart failure. However, the demand for donor hearts significantly outweighs the supply. Hearts are sourced from donors following brain death, which exposes donor hearts to substantial pathophysiological perturbations that can influence heart transplant success and recipient survival. Although significant advances in recipient selection, donor and HTx recipient management, immunosuppression, and pretransplant mechanical circulatory support have been achieved, primary graft dysfunction after cardiac transplantation continues to be an important cause of morbidity and mortality. Animal models, when appropriate, can guide/inform medical practice, and fill gaps in knowledge that are unattainable in clinical settings. Consequently, we performed a systematic review of existing animal models that incorporate donor brain death and subsequent HTx and assessed studies for scientific rigor and clinical relevance. Following literature screening via the U.S National Library of Medicine bibliographic database (MEDLINE) and Embase, 29 studies were assessed. Analysis of included studies identified marked heterogeneity in animal models of donor brain death coupled to HTx, with few research groups worldwide identified as utilizing these models. General reporting of important determinants of heart transplant success was mixed, and assessment of posttransplant cardiac function was limited to an invasive technique (pressure-volume analysis), which is limitedly applied in clinical settings. This review highlights translational challenges between available animal models and clinical heart transplant settings that are potentially hindering advancement of this field of investigation.

Influence of donor brain death duration on outcomes following heart transplantation: A United Network for Organ Sharing Registry analysis

OBJECTIVES

We hypothesized that an increased duration of donor brain death may worsen survival following orthotopic heart transplantation.

METHODS

The United Network for Organ Sharing Registry was queried for first-time, adult recipients of heart transplant from 2006 to 2018. Cox proportional hazards with penalized smooth splines was used to stratify patients based on donor brain death interval: shorter (<22 hours), reference (22-42 hours), and longer (>42 hours). Overall survival was estimated using Kaplan-Meier and Cox proportional hazards models.

RESULTS

A total of 22,960 patients met study criteria (9.2% shorter, 55.0% reference, and 35.8% longer). Longer brain death duration recipients were more likely to have a later year of transplant and have a mechanical bridge to transplant, whereas longer duration donors were more likely to be black and die of anoxia compared with shorter duration and reference donors. Compared with reference, neither shorter (hazard ratio, 1.02; 95% confidence interval, 0.94-1.12) nor longer donor brain death interval (hazard ratio, 1.01; 95% CI, 0.94-1.08) was associated with posttransplant survival in either unadjusted or multivariable analyses (both P values >0.6).

CONCLUSIONS

Longer duration of brain death was not associated with worse survival following heart transplantation. Donors with prolonged interval of brain death should not necessarily be excluded based on brain death period alone.

Does duration of donor brain injury impact heart transplantation outcomes?

AIM

We aimed to study the implications of pre-transplantation time intervals on HT outcomes.

METHODS

Brain injury time (BIT) was defined as the period from the donor brain injury to brain death declaration. Brain death interval (BDI) was defined as the period from brain death to application of an aortic cross-clamp during donor heart procurement. Allograft ischemia was defined as the time from donor aortic cross-clamp to aortic unclamping. End points included mortality and rejections.

RESULTS

Between 1997 and 2017, we assessed 173 patients. Kaplan-Meier analyses showed that prolonged donor BIT, BDI, allograft ischemia, and total injury time had no significant effect on mortality and rejections. Patients were subdivided into short BIT (<97 hours, n = 87) and long BIT (≥97 hours, n = 86) groups. No differences in rejection scores nor in time to first rejection were noted. Kaplan-Meier analysis showed a similar long-term survival in the two groups. Sub-analysis of both groups according to their median BDI (12 hours) revealed no differences in mortality or time to rejection.

CONCLUSIONS

Pre-transplantation time intervals do not affect mortality or rejection. Our findings have important clinical implications regarding HT allocation and organ availability.

Impact of Donor Brain Death Duration on Outcomes After Lung Transplantation

BACKGROUND

Donor brain death duration (BDD) may impact posttransplant graft function and survival in lung transplant.

METHODS

We queried the 2007 to 2018 United Network for Organ Sharing Registry for adult recipients undergoing first-time isolated lung transplant. Cox proportional hazard modeling with splines enabled identification of 3 donor brain death intervals for subsequent analysis: short (<24 hours), reference (24-60 hours), and long (>60 hours). The primary outcome was posttransplant survival.

RESULTS

In total, 19,721 donors and recipients met inclusion criteria. Median time from donor brain death until cross-clamp was 36.6 hours (interquartile range, 19.5). Unadjusted overall survival between cohorts was equivalent (log-rank P = .42); however, longer BDD was associated with improved bronchiolitis obliterans syndrome (BOS)-free survival (log-rank P < .001). On multivariable Cox proportional hazards regression, BDD was not associated with recipient survival (P > .05). Similarly, logistic regression did not identify an independent association between BDD and primary graft dysfunction (P > .05). Increased BDD was, however, associated with a decreased risk of acute rejection (long vs reference; adjusted odds ratio, 0.78; 95% confidence interval, 0.64-0.94) and improved BOS-free survival (long vs reference; adjusted hazard ratio, 0.88; 95% confidence interval, 0.81-0.96).

CONCLUSIONS

Donor BDD is not associated with posttransplant survival or primary graft dysfunction. Long donor BDD, however, is associated with a decreased risk for acute rejection and improved BOS-free survival. Therefore, lung allografts from donors with a prolonged length of time from brain death until explant should not be viewed less favorably by donor selection centers.

Brain death interval and relationship to outcomes of pediatric cardiac transplantation

BACKGROUND

We sought to analyze brain death interval and outcomes of pediatric cardiac transplantation using national registry data.

METHODS

We retrospectively evaluated a pediatric cohort from the UNOS registry from 2005 to 2014. We restricted the donor cohort to those with a primary central nervous system event as the cause of hospitalization. Brain death interval (BDI) was defined as the time between hospital admission and organ procurement. Primary outcomes were recipient and graft survival time. Logistical regression modeling was used for multivariable analysis.

RESULTS

The donor cohort included 2565 cases. Multivariable analysis demonstrated no relationship between BDI and recipient or graft survival time. For patient survival time, the lowest HR was 0.94 (0.63-1.39), P = 0.531; for graft survival time, the lowest HR was 0.89 (0.53-1.49), P = 0.563. We obtained similar results using a non-restricted donor cohort.

CONCLUSIONS

There was no clear relationship between BDI and recipient or graft survival after pediatric cardiac transplantation.

Predictors of Organ Donation Among Patients With Brain Death in the Intensive Care Unit

INTRODUCTION

Despite the improved care of potential organ donors with probable brain death (BD) in the intensive care unit (ICU), few epidemiologic and clinical data are available in developing countries.

OBJECTIVES

To evaluate ICU patients with suspected BD aiming to identify factors possibly related to success (organ donation) or failure (nondonation).

METHODS

Retrospective cohort study, from the patient records of an adult ICU of a Brazilian teaching hospital for 12 months. Data were tabulated, and descriptive statistics and univariate and multivariate analyses were performed.

RESULTS

During the study period, 85 patients with acute neurologic diseases and suspected BD were admitted to the ICU and included for analysis. Of these, there were 9 organ donors (7 liver and 9 kidney donors); 77.7% were men, with a mean age of 39.6 years and admission Acute Physiology and Chronic Health Evaluation II of 25.5. Two-thirds of the patients were victims of trauma. The mean time between acute neurologic event and organ withdrawal was 269 hours. The main prognostic factors related to the success of organ donation were the maximum serum lactate and creatinine levels during ICU admission.

CONCLUSIONS

The main clinical factors correlated with nonevolution for organ donation among ICU patients with clinical suspicion of BD were related to patient severity and organic dysfunction: serum lactate and creatinine level. Clinical care and monitoring are emphasized to improve the efficiency of the donation process.

Guidelines for the management of a brain death donor in the rhesus macaque: A translational transplant model

Introduction

The development of a translatable brain death animal model has significant potential to advance not only transplant research, but also the understanding of the pathophysiologic changes that occur in brain death and severe traumatic brain injury. The aim of this paper is to describe a rhesus macaque model of brain death designed to simulate the average time and medical management described in the human literature.

Methods

Following approval by the Institutional Animal Care and Use Committee, a brain death model was developed. Non-human primates were monitored and maintained for 20 hours after brain death induction. Vasoactive agents and fluid boluses were administered to maintain hemodynamic stability. Endocrine derangements, particularly diabetes insipidus, were aggressively managed.

Results

A total of 9 rhesus macaque animals were included in the study. The expected hemodynamic instability of brain death in a rostral to caudal fashion was documented in terms of blood pressure and heart rate changes. During the maintenance phase of brain death, the animal’s temperature and hemodynamics were maintained with goals of mean arterial pressure greater than 60mmHg and heart rate within 20 beats per minute of baseline. Resuscitation protocols are described so that future investigators may reproduce this model.

Conclusion

We have developed a reproducible large animal primate model of brain death which simulates clinical scenarios and treatment. Our model offers the opportunity for researchers to have translational model to test the efficacy of therapeutic strategies prior to human clinical trials.

Predictors of 1-year mortality in heart transplant recipients: a systematic review and meta-analysis

Objective

A systematic summary of the observational studies informing heart transplant guideline recommendations for selection of candidates and donors has thus far been unavailable. We performed a meta-analysis to better understand the impact of such known risk factors.

Methods

We systematically searched and meta-analysed the association between known pretransplant factor and 1-year mortality identified by multivariable regression models. Our review used the Grading of Recommendations, Assessment, Development and Evaluation for assessing the quality of assessment. We pooled risk estimates by using random effects models.

Results

Recipient variables including age (HR 1.16 per 10-year increase, 95% CI 1.10–1.22, high quality), congenital aetiology (HR 2.35, 95% CI 1.62 to 3.41, moderate quality), diabetes (HR 1.37, 95% CI 1.15 to 1.62, high quality), creatinine (HR 1.11 per 1 mg/dL increase, 95% CI 1.06 to 1.16, high quality), mechanical ventilation (HR 2.46, 95% CI 1.48 to 4.09, low quality) and short-term mechanical circulatory support (MCS) (HR 2.47, 95% CI 1.04 to 5.87, low quality) were significantly associated with 1-year mortality. Donor age (HR 1.20 per 10-year increase, 95% CI 1.14 to 1.26, high quality) and female donor to male recipient sex mismatch (HR 1.38, 95% CI 1.06 to 1.80, high quality) were significantly associated with 1-year mortality. None of the operative factors proved significant predictors.

Conclusion

High-quality and moderate-quality evidence demonstrates that recipient age, congenital aetiology, creatinine, pulsatile MCS, donor age and female donor to male recipient sex mismatch are associated with 1-year mortality post heart transplant. The results of this study should inform future guideline and predictive model development.

Sex differences on solid organ histological characteristics after brain death1

PURPOSE

To investigate gender differences in the evolution of the inflammatory process in rats subjected to brain death (BD).

METHODS

Adult Wistar rats were divided into three groups: female; ovariectomized female; and male rats. BD was induced using intracranial balloon inflation and confirmed by maximal pupil dilatation, apnea, absence of reflex, and drop of mean arterial pressure. Six hours after BD, histological evaluation was performed in lungs, heart, liver and kidneys, and levels of inflammatory proteins, estrogen, progesterone, and corticosterone were determined in plasma.

RESULTS

In the lungs, females presented more leukocyte infiltration compared to males (p<0.01). Ovariectomized female rat lungs were more hemorrhagic compared to other groups (p<0.001). In the heart, females had higher leukocyte infiltration and tissue edema compared to males (p<0.05). In the liver and kidneys, there were no differences among groups. In female group estradiol and progesterone were sharply reduced 6 hours after BD (p<0.001) to values observed in ovariectomized females and males. Corticosterone levels were similar.

CONCLUSIONS

Sex hormones influence the development of inflammation and the status of organs. The increased inflammation in lungs and heart of female rats might be associated with the acute reduction in female hormones triggered by BD.