An Adapted Process and Organ Procurement Perspective on Heart Retransplantation for a Healthy Heart’s Third Life

As organ procurement organizations nationwide see an increased opportunity to retransplant already transplanted hearts, we would like to share the overview and process of our 2 successful cases. Heart retransplantation increased our cardiac placement rates by 2.64% and 2% in 2015 and 2019, respectively. Spread across a nation that sees over 3500 heart placements annually, a 2% increase would be substantial. Since 2009, our cases stand as the only documented heart retransplantations in the United States. However, United Network for Organ Sharing data shows that potential exists. From a facilitation perspective, we have developed a protocol to ease the matching process. From a surgical perspective, these cases had no complications and saved 2 lives, with each heart now beating in a third person. We hope that by sharing our process and success, we can familiarize fellow organ procurement organizations and transplant communities with this viable opportunity.

Donor heart preservation with hypoxic conditioned medium derived from bone marrow mesenchymal stem cell improves cardiac function in a heart transplantation model

Background: In heart transplantation, donor hearts inevitably suffer from ischemia/reperfusion (I/R) injury, which leads to primary graft dysfunction and affects patients’ survival rate. Bone marrow mesenchymal stem cells (BMSCs) have been reported to attenuate myocardial I/R injury via their paracrine effects, which can be enhanced by hypoxic preconditioning. We hypothesized that the donor heart preservation with hypoxic conditioned medium (CdM) derived from BMSCs would improve post-transplant graft function. Methods: Normoxic or hypoxic CdM were isolated from rat BMSCs cultured under normoxic (20% O2) or hypoxic (1% O2) condition. Donor hearts were explanted, stored in cardioplegic solution supplemented with either a medium (Vehicle), normoxic CdM (N-CdM), or hypoxic CdM (H-CdM), and then heterotopically transplanted. Antibody arrays were performed to compare the differences between hypoxic and normoxic CdM.Results: After heart transplantation, the donor heart preservation with normoxic CdM was associated with a shorter time to return of spontaneous contraction and left ventricular systolic diameter, lower histopathological scores, higher ejection fraction, and fractional shortening of transplanted hearts. The cardioprotective effects may be associated with the inhibition of apoptosis and inflammation, as reflected by less TUNEL-positive cells and lower levels of plasma proinflammatory cytokines (Interleukin-1β, Interleukin-6, tumor necrosis factor-α) and cardiac troponin I in the N-CdM group compared with the vehicle group. These therapeutic effects can be further enhanced by hypoxic preconditioning. Antibody arrays revealed that nine proteins were significantly increased in hypoxic CdM compared with normoxic CdM. Furthermore, compared with vehicle and N-CdM groups, the protein levels of PI3K and p‐Akt/Akt ratio in the transplanted hearts significantly increased in the H-CdM group. However, no significant difference was found in the phosphorylation of Smad2 and Smad3 for the donor hearts among the three groups. Conclusions: Our results indicate that the cardioplegic solution-enriched with hypoxic CdM can be a novel and promising preservation solution for donor hearts.

A nationwide 16 year analysis of trends and impact of arrythmias in transplant recipients

Background Orthotopic heart transplantation is the most effective long-term therapy for end-stage heart disease. Denervation of transplanted heart with the loss of autonomic modulation, vasculopathy, utilization of immunosuppressant drugs, and risk of allograft rejection may result in change in the prevalence of arrhythmias in transplanted hearts. Purpose To describe the trends, distribution and the clinical impact of arrhythmias in transplanted hearts in a large nationwide population. Methods We queried the National Inpatient Sample with administrative codes. Cardiac transplant patients were identified using procedure ICD-9-CM codes 37.5 and 33.6. Common arrhythmias were extracted using appropriate validated ICD-9-CM codes. Statistical Analysis System (SAS) version 9.4 was used for analysis of data. Results There was a total of 30,020 hospitalizations of heart transplant recipients between 1999 and 2014 in the United States and 16342 (54.4%) of these had arrhythmias. The prevalence of total arrhythmias increased from 53.6% (n=1,158) in 1999 to 67.3% (n=1,575) in 2014. The most common arrhythmia was atrial fibrillation (26.83%) followed by ventricular tachycardia (22.86%) and the prevalence of individual arrhythmias is as shown in Figure 1. Cardiogenic shock was higher in transplanted hearts with arrhythmias when compared with patients without arrhythmias (25.96% vs 18.18%; p<0.001). Transplant recipients with arrhythmias were also associated with an increased use of mechanical circulatory device (18.22% vs 12.67%, p<0.001). The use of implantable cardiac defibrillators and permanent pacemaker was also higher in the arrhythmia group (2.19% vs 0.63% and 40.43% vs 30.24% respectively, p<0.0001). However, there was no significant difference in inpatient mortality between transplant recipients with arrhythmias and without arrhythmias (7.72% vs 6.90%, p=0.225). Further, there was no significant difference in frequency of strokes between the groups (4.98% vs 5.08%; p=0.857). The total hospital cost when adjusted for inflation was significantly higher in the arrhythmic patients, with an average cost of about $570,415±9,590 vs $439,707±8362 in patients without arrhythmias (p<0.0001). The mean length of hospitalization was 44.2±0.8 days in patients with arrhythmias compared to 33.9±0.8 days in patients without arrhythmias (p<0.0001). Conclusion A significant proportion of patients with heart transplant have cardiac arrhythmias and are associated with worse in-hospital outcomes of cardiogenic shock, increased length of stay, and cost of hospitalization. However, they are not associated with worse inpatient mortality. Funding Acknowledgement Type of funding source: None

Donor Heart Preservation with Hypoxic Conditioned Medium Derived from Bone Marrow Mesenchymal Stem cell improves Cardiac Function in a Heart Transplantation Model

Background: In heart transplantation, donor hearts inevitably suffer from ischemia/reperfusion (I/R) injury, which leads to primary graft dysfunction and affects patients’ survival rate. Bone marrow mesenchymal stem cells (BMSCs) have been reported to attenuate myocardial I/R injury via their paracrine effects, which can be enhanced by hypoxic preconditioning. We hypothesized that the donor heart preservation with hypoxic conditioned medium derived from BMSCs (CM-BMSCs) would improve post-transplant graft function. Methods: Normoxic CM and hypoxic CM were isolated from rat BMSCs cultured under normoxic (20% O2) or hypoxic (1% O2) condition. Donor hearts were explanted, stored in cardioplegic solution supplemented with either a medium (Vehicle), normoxic CM (N-CM), or hypoxic CM (H-CM), and then heterotopically transplanted. Antibody arrays were performed to compare the differences between hypoxic CM and normoxic CM.Results: After heart transplantation, the donor heart preservation with normoxic CM was associated with shorter re-beating time, histopathological scores, and left ventricular systolic diameter, higher ejection fraction, and fractional shortening of transplanted hearts. These protective effects may be associated with the inhibition of apoptosis and inflammation, as reflected by less TUNEL-positive cells and lower levels of serum proinflammatory cytokines (Interleukin-1β, Interleukin-6, tumor necrosis factor-α) and cardiac troponin I in the N-CM group compared with the vehicle group. These therapeutic effects can be further enhanced by hypoxic preconditioning. Antibody arrays revealed that nine proteins were significantly increased in hypoxic CM compared with normoxic CM. Furthermore, compared with vehicle and N-CM groups, the protein levels of PI3K and p‐Akt/Akt ratio in the transplanted hearts significantly increased in the H-CM group. Conclusions: Our results indicate that cardioplegic solution-enriched with hypoxic CM-BMSCs can be a novel and promising preservation solution for donor hearts.

The role of exogenous CD4+CD25+ Treg cells in heart transplantation tolerance

Background: CD4+CD25+regulatory T cells (CD4+CD25+ Treg cells) play major roles in immune regulation. Previous studies showed CD4+CD25+ Treg cells can maintain peripheral immune tolerance and increase survival time of transplanted organs. However, the biological characteristics and the functional roles of these exogenous CD4+CD25+ Treg cells in transplantation tolerance remain unknown. The current study was conducted to observe the effect of CD4+CD25+ Treg cells on heart allograft in rats and to investigate the underlying mechanism of the exogenous CD4+CD25+ Treg cells.Methods: 5 x 107 spleen cells of SD rats were inoculated into the thymus gland of Wistar rats. The level of CD4+CD25+ Treg cells was examined by the flow cytometry method, and the biological activity of CD4+CD25+ Treg cells was detected by the 3H-TdR method. Hearts were transplanted from SD rats (donors) to Wistar rats (recipients) and the animals were assigned into four groups: HT, HT+Ii,HT+Treg, HT+Treg+Ii. At various time points after the transplantation, the transplanted hearts were collected and histologically examined. The rate of lymphocyte apoptosis and T cell subsets in the peripheral blood of Wistar rats were analyzed with flow cytometry.Results: The CD4+CD25+ Treg cells in Wistar rats were sharply increased. The results show that these exogenous CD4+CD25+ Treg cells have a significant inhibitory effect: the mean survival time of the transplanted hearts was 8.1 ± 1.2 days, 35.7 ± 4.7 days，53.7 ± 6.2 days, 75.7 ± 11.3 days in HT, HT+Ii, HT+Treg, and HT+Ii+Treg group, respectively (n = 12-14/group). Among them, HT vs. HT+Treg and HT vs. HT+Treg+Ii were both significantly different (p < 0.001). In addition, we found that exogenous CD4+CD25+ Treg cells improved the pathological changes of the transplanted hearts, increased the rate of lymphocyte apoptosis, upregulated CD3+CD8+T cells, and suppressed CD3+CD4+ T cells.Conclusions: Exogenous CD4+CD25+ Treg cells appear to induce heart transplantation tolerance. The underlying mechanism is associated with the exogenous CD4+CD25+ Treg cells-dependent induction of lymphocyte apoptosis and modulation of the ratio of T cell subsets.

Myocardial bridging in the era of a drug epidemic: a case report addressing the need to revisit donor organ assessment

Background Myocardial bridging (MB), though typically a benign finding, may occasionally lead to syncope, myocardial infarction, arrhythmia, or sudden death. Surgical denervation of transplanted hearts complicates the management of such incidentally detected post-transplant coronary anomalies due to the lack of classic ischaemic symptoms. Case summary A middle-aged female underwent an uncomplicated cardiac transplantation from a healthy male donor in his early 20s who had suffered a cardiac arrest while using cocaine. Given the young donor age, a pre-transplant coronary angiogram (CAG) was deferred. However, 6-week post-transplant, routine CAG, and intravascular ultrasound revealed an extensive MB spanning a significant portion of the left anterior descending coronary artery with substantial myocardium at risk. A stress test with myocardial perfusion imaging performed to evaluate the functional significance of the bridge did not reveal any perfusion abnormalities in the myocardium at risk. Discussion In current practice, younger donors often do not undergo pre-transplantation CAG routinely performed in older donors given the lower prevalence of significant coronary disease. However, post-operatively this young donor was found to have passed on a potentially life-threatening MB to a denervated recipient, who cannot manifest typical anginal symptoms during ischaemia, thereby challenging providers to choose among strategies of watchful waiting, risk stratification, or pre-emptive intervention. In retrospect, the donor’s mode of death may have signalled an underlying structural abnormality that warranted further pre-transplant characterization. In order to ensure optimal quality of transplanted hearts, young donors may warrant pre-transplant CAG despite their age, particularly those with a history of drug use or suspicious mode of death.