Extended Static Hypothermic Preservation In Cardiac Transplantation: A Case Report

Utilization of hepatitis C virus infected donors in heart transplant recipients with elevated MELD-XI score

BACKGROUND

The advent of direct-acting antivirals has helped to increase the safe utilization of organs from hepatitis C virus positive (HCV+) donors. However, the outcomes of heart transplantation (HT) using an HCV+ donor are unclear in recipients with underlying liver disease represented by an elevated model for end-stage liver disease excluding international normalized ratio (MELD-XI).

METHODS

The United Network of Organ Sharing database was queried from Jan 2016 to Dec 2021. Post-transplant outcomes stratified by recipient MELD-XI score (low <10.37, medium, 10.38-13.39, and high >13.4) was compared between patients with HT from HCV+ (N = 792) and patients with HT from HCV-negative donors (N = 15,266).

RESULTS

The median MELD-XI score was comparable (HCV+, 12.1, vs. HCV-negative, 11.8, p = .37). In the HCV+ group, donors were older (33 vs. 31 years, p < .001). Ischemic time of donor hearts (3.48 vs. 3.28 h, p < .001) and travel distance (250 vs. 157 miles, p < .001) were longer in HCV+ group. In the Kaplan Meier analysis with a median follow-up of 750 days, survival was comparable between the two groups (2-year survival, MELD-XI Low: HCV+, 92.4 ± 3.6% vs. HCV-negative, 91.1 ±.8%, p = .83, Medium: HCV+ 89.2 ± 4.3% vs. HCV-negative, 88.2 ± 1.0%, p = .68, and High: HCV+, 84.9 ± 4.5% vs. HCV-negative, 84.6 ± 1.1%, p = .75) In multivariate Cox hazard models, HCV donors were not associated with mortality in each MELD-XI subgroup (Low: adjusted hazard ratio (aHR), 1.02, p = .94; Medium: aHR, .95, p = .81; and High: aHR, .93, p = .68).

CONCLUSION

Utilization of HCV+ hearts was not associated with an increased risk of adverse outcomes in recipients with an elevated MELD- XI score.

A Paradigm Shift in Heart Preservation: Improved Post-transplant Outcomes in Recipients of Donor Hearts Preserved With the SherpaPak System

Traditional ice storage has been the historic standard for preserving donor's hearts. However, this approach provides variability in cooling, increasing risks of freezing injury. To date, no preservation technology has been reported to improve survival after transplantation. The Paragonix SherpaPak Cardiac Transport System (SCTS) is a controlled hypothermic technology clinically used since 2018. Real-world evidence on clinical benefits of SCTS compared to conventional ice cold storage (ICS) was evaluated. Between October 2015 and January 2022, 569 US adults receiving donor hearts preserved and transported either in SCTS (n = 255) or ICS (n = 314) were analyzed from the Global Utilization And Registry Database for Improved heArt preservatioN (GUARDIAN-Heart) registry. Propensity matching and a subgroup analysis of >240 minutes ischemic time were performed to evaluate comparative outcomes. Overall, the SCTS cohort had significantly lower rates of severe primary graft dysfunction (PGD) ( p = 0.03). When propensity matched, SCTS had improving 1-year survival ( p = 0.10), significantly lower rates of severe PGD ( p = 0.011), and lower overall post-transplant MCS utilization ( p = 0.098). For patients with ischemic times >4 hours, the SCTS cohort had reduced post-transplant MCS utilization ( p = 0.01), reduced incidence of severe PGD ( p = 0.005), and improved 30-day survival ( p = 0.02). A multivariate analysis of independent risk factors revealed that compared to SCTS, use of ice results in a 3.4-fold greater chance of severe PGD ( p = 0.014). Utilization of SCTS is associated with a trend toward increased post-transplant survival and significantly lower severe PGD and MCS utilization. These findings fundamentally challenge the decades-long status quo of transporting donor hearts using ice.

Outcomes of Heart Transplantation Using a Temperature-controlled Hypothermic Storage System

BACKGROUND

The SherpaPak Cardiac Transport System is a novel technology that provides stable, optimal hypothermic control during organ transport. The objectives of this study were to describe our experience using the SherpaPak system and to compare outcomes after heart transplantation after using SherpaPak versus the conventional static cold storage method (non-SherpaPak).

METHODS

From 2018 to June 2021, 62 SherpaPak and 186 non-SherpaPak patients underwent primary heart transplantation at Stanford University with follow-up through May 2022. The primary end point was all-cause mortality, and secondary end points were postoperative complications. Optimal variable ratio matching, cox proportional hazards regression model, and Kaplan-Meier survival analyses were performed.

RESULTS

Before matching, the SherpaPak versus non-SherpaPak patients were older and received organs with significantly longer total allograft ischemic time. After matching, SherpaPak patients required fewer units of blood product for perioperative transfusion compared with non-SherpaPak patients but otherwise had similar postoperative outcomes such as hospital length of stay, primary graft dysfunction, inotrope score, mechanical circulatory support use, cerebral vascular accident, myocardial infarction, respiratory failure, new renal failure requiring dialysis, postoperative bleeding or tamponade requiring reoperation, infection, and survival.

CONCLUSIONS

In conclusion, this is one of the first retrospective comparison studies that evaluated the outcomes of heart transplantation using organs preserved and transported via the SherpaPak system. Given the excellent outcomes, despite prolonged total allograft ischemic time, it may be reasonable to adopt the SherpaPak system to accept organs from a remote location to further expand the donor pool.

Applications of Tissue Decellularization Techniques in Ventricular Myocardial Biofabrication

Ischemic heart disease is the leading cause of death around the world, and though the advent of coronary revascularization has revolutionized its treatment, many patients who sustain ischemic injury to the heart will go on to develop heart failure. Biofabrication of ventricular myocardium for replacement of irreversibly damaged ischemic myocardium is sought after as a potential therapy for ischemic heart failure, though challenges in reliably producing this biomaterial have limited its clinical application. One method that shows promise for generation of functional myocardium is the use of tissue decellularization to serve as a scaffold for biofabrication. This review outlines the methods, materials, challenges, and prospects of tissue decellularization techniques for ventricular myocardium biofabrication. Decellularization aims to preserve the architecture and composition of the extracellular matrix of the tissue it is applied to, allowing for the subsequent implantation of stem cells of the desired cell type. Decellularization can be achieved with multiple reagents, most of which have detergent properties. A variety of cell types can be implanted in the resulting scaffold, including cardiac progenitor cells, and embryonic or induced pluripotent stem cells to generate a range of tissue, from patches to beating myocardium. The future of this biofabrication method will likely emphasize patient specific tissue engineering to generate complex 3-dimensional constructs that can replace dysfunctional cardiac structures.

Cardiac Surgery in Advanced Heart Failure

Mechanical circulatory support and heart transplantation are established surgical options for treatment of advanced heart failure. Since the prevalence of advanced heart failure is progressively increasing, there is a clear need to treat more patients with mechanical circulatory support and to increase the number of heart transplantations. This narrative review summarizes recent progress in surgical treatment options of advanced heart failure and proposes an algorithm for treatment of the advanced heart failure patient at >65 years of age.