Donor heart preservation in an empty beating state under mild hypothermia

Cardiac Graft Assessment in the Era of Machine Perfusion: Current and Future Biomarkers

Heart transplantation remains the treatment of reference for patients experiencing end‐stage heart failure; unfortunately, graft availability through conventional donation after brain death is insufficient to meet the demand. Use of extended‐criteria donors or donation after circulatory death has emerged to increase organ availability; however, clinical protocols require optimization to limit or prevent damage in hearts possessing greater susceptibility to injury than conventional grafts. The emergence of cardiac ex situ machine perfusion not only facilitates the use of extended‐criteria donor and donation after circulatory death hearts through the avoidance of potentially damaging ischemia during graft storage and transport, it also opens the door to multiple opportunities for more sensitive monitoring of graft quality. With this review, we aim to bring together the current knowledge of biomarkers that hold particular promise for cardiac graft evaluation to improve precision and reliability in the identification of hearts for transplantation, thereby facilitating the safe increase in graft availability. Information about the utility of potential biomarkers was categorized into 5 themes: (1) functional, (2) metabolic, (3) hormone/prohormone, (4) cellular damage/death, and (5) inflammatory markers. Several promising biomarkers are identified, and recommendations for potential improvements to current clinical protocols are provided.

Effect of Shenfu Injection on Isolated Empty Beating Hearts from Miniature Pigs

OBJECTIVE

To investigate the effect of Shenfu (SF) injection on donor heart preservation.

METHODS

Twelve pigs were randomly divided into SF group (n=6) and control group (n=6). After eight hours of perfusion, the differences in hemoglobin, the expression of Bcl-2 and BAX, and changes in the myocardial ultrastructure were compared to illustrate the effects of SF injection in heart preservation.

RESULTS

The differences in free hemoglobin between the SF group and the control group were statistically significant (P=0.001), and there was significant interaction of groups with times (P=0.019), but the perfusion time may not be associated with the hemoglobin concentration (P=0.616). According to Western blotting analysis, the expression of Bcl-2 was higher in the SF group than in the control group, while the expression of BAX was not different between the two groups. As to ultrastructural changes, both groups exhibited mitochondrial swelling and myofilament lysis, but the degree of damage in the SF group was smaller.

CONCLUSION

Our study suggests that the application of SF injection for heart preservation may protect against cardiomyocytes and erythrocytes apoptosis, and Bcl-2 protein may play a role in these physiological processes.

Induced functional modulations of isolated large mammalian hearts

In this study we used Visible Heart® methodologies featuring cyclic temperature modulation of porcine hearts in order to establish characteristic temperature responses. This isolated and perfused model is a more predictable and modifiable analog for human heart preservation and isolates the response of the cardiac tissue. We comprehensively monitored isolated porcine hearts undergoing temperature change and demonstrated optimization of isolated cardiac function under mild hypothermia. We tracked metrics of cardiac function as continuous variables during temperature changes (~ 31 to 39 °C), eliciting a well-defined reduction in metabolic demand and in heart rate modulation. Optimization of function appeared to occur around 34.7 ± 0.9 °C (n = 13). Cardiac response was further investigated in the presence of active pacing in order to assess pacing capture and the heart's functional response without a means of regulating rate. Our results may have direct clinical implications for emerging heart preservation methods prior to transplantation, as well as benefits for investigators using isolated heart models for preclinical device testing. Clinically, this porcine model is a basis for finding new ways to extend the window of viability for transplantable organs, thereby restoring or improving graft function and potentially enhancing recipient outcomes.

Transplantation of Hearts Donated after Circulatory Death

Cardiac transplantation has become limited by a critical shortage of suitable organs from brain-dead donors. Reports describing the successful clinical transplantation of hearts donated after circulatory death (DCD) have recently emerged. Hearts from DCD donors suffer significant ischemic injury prior to organ procurement; therefore, the traditional approach to the transplantation of hearts from brain-dead donors is not applicable to the DCD context. Advances in our understanding of ischemic post-conditioning have facilitated the development of DCD heart resuscitation strategies that can be used to minimize ischemia-reperfusion injury at the time of organ procurement. The availability of a clinically approved ex situ heart perfusion device now allows DCD heart preservation in a normothermic beating state and minimizes exposure to incremental cold ischemia. This technology also facilitates assessments of organ viability to be undertaken prior to transplantation, thereby minimizing the risk of primary graft dysfunction. The application of a tailored approach to DCD heart transplantation that focuses on organ resuscitation at the time of procurement, ex situ preservation, and pre-transplant assessments of organ viability has facilitated the successful clinical application of DCD heart transplantation. The transplantation of hearts from DCD donors is now a clinical reality. Investigating ways to optimize the resuscitation, preservation, evaluation, and long-term outcomes is vital to ensure a broader application of DCD heart transplantation in the future.

Keeping donor hearts in completely beating status with normothermic blood perfusion for transplants

BACKGROUND

Previously, we reported the preservation method of donor hearts in an empty beating status with mild hypothermic perfusion. To completely avoid cardiac arrest and myocardial ischemia, we performed the beating preservation technique from procurement of hearts to transplants and assessed its efficacy for long-term preservation and feasibility for heart transplantation.

METHODS

Thirty-two swine donor hearts were preserved in beating status (group A, n = 8 pairs, perfused continuously with normothermic blood) or in static cold storage (group B, n = 8 pairs, stored in 4°C histidine-tryptophan-ketoglutarate solutions) for 8 hours. Then the donor hearts were implanted either in beating or static status. During transplantation, the incidence of arrhythmia, duration of anastomosis and cardiopulmonary bypass, and dosage of inotropic drugs were recorded. Hemodynamics of left ventricle and serum level of creatine kinase-MB were measured during transplantation. Myocardial ultrastructure was observed.

RESULTS

Compared with group B, in group A the anastomotic time was significantly longer, the cardiopulmonary bypass time was significantly shorter, the cardiac output was larger, and the incidence of arrhythmia, dosage of cardiovascular-active drugs, and serum level of creatine kinase-MB were lower. After declamping for 2 hours and 3.5 hours, the left ventricular hemodynamics of group A was significantly better than that of group B. The myocardial ultrastructure of group A was superior to that of group B.

CONCLUSIONS

Preservation of donor hearts in beating status with continuous, normothermic, blood perfusion is an effective approach for long-term preservation and is appropriate for heart transplantation.