Maximizing donor allocation: A review of UNOS region 9 donor heart turn-downs

Short stature is a risk factor for heart transplant morbidity and mortality

BACKGROUND

Short stature is associated with mortality after cardiac surgery and may increase size mismatch risk among transplant recipients. Yet, stature's impact on heart transplant outcomes is not well-characterized.

METHODS

The Scientific Registry of Transplant Recipients was queried for data on all adult heart transplants in the United States from 2000 to 2022. Recipients were stratified into five cohorts by sex-corrected stature. Morbidity was assessed with Kruskal-Wallis and chi-squared tests. Mortality was analyzed using Kaplan-Meier estimation. Risk factors for mortality were assessed with multivariable Cox regression.

RESULTS

Among 43,420 transplant recipients, 5321 (12.2%) had short stature (females >4'11″ & ≤5'1″; males >5'4″ & ≤5'7″) and 765 (1.8%) had very short stature (females ≤4'11″; males ≤5'4″). Very short stature patients had higher waitlist status (1A and 1), more congenital heart disease, and received more oversized donor hearts than other cohorts (all p < 0.05). Very short stature patients had decreased 30-day, 1-, 5-, and 10-year survival (94.6%, 84.3%, 69.3% and 52.5%, respectively, all p < 0.001), but less acute rejection (p = 0.005) and comparable stroke rates (p = 0.107). On multivariable regression adjusting for congenital heart disease and oversized donor hearts, very short and short stature were associated with 10-year mortality (hazard ratios: 1.40 and 1.12, respectively, both p < 0.005).

CONCLUSIONS

Short stature confers increased mortality risk for heart transplant recipients and merits inclusion in prognostic models.

The Role of Purinergic Signaling in Heart Transplantation

Heart transplantation remains the optimal treatment option for patients with end-stage heart disease. Growing evidence demonstrates that purinergic signals mediated by purine nucleotides and nucleosides play vital roles in heart transplantation, especially in the era of ischemia-reperfusion injury (IRI) and allograft rejection. Purinergic signaling consists of extracellular nucleotides and nucleosides, ecto-enzymes, and cell surface receptors; it participates in the regulation of many physiological and pathological processes. During transplantation, excess adenosine triphosphate (ATP) levels are released from damaged cells, and driver detrimental inflammatory responses largely via purinergic P2 receptors. Ecto-nucleosidases sequentially dephosphorylate extracellular ATP to ADP, AMP, and finally adenosine. Adenosine exerts a cardioprotective effect by its anti-inflammatory, antiplatelet, and vasodilation properties. This review focused on the role of purinergic signaling in IRI and rejection after heart transplantation, as well as the clinical applications and prospects of purinergic signaling.

Better together: a reappraisal of heterotopic heart transplantation

Heterotopic heart transplantation (HHT) is rare in the modern era. When used as a biologic left ventricular assist, HHT provides pulsatile flow, supports the left ventricle with a physiologic cardiac output, responds to humoral stimuli, and with modern immunosuppression may offer long-term untethered survival. This study was undertaken to compare survival of HHT with orthotopic heart transplantation (OHT) to assess its viability in the modern era. In the United Network for Organ Sharing database, from January 1999 to December 2020, there were 27691 bicaval OHT, 13836 biatrial OHT, 1271 total OHT, and 51 HHT with sufficient follow-up. Survival was analyzed using restricted mean survival time (RMST) through 4 years as the outcome. In the first 4 years after transplant, compared with HHT, differences in RMST were 0.1 years (99% CI: -0.4 to 0.5 years) for bicaval OHT, 0.0 years (99% CI: -0.4 to 0.5 years) for biatrial OHT, and 0.0 years (99% CI: -0.5 to 0.4 years) for total OHT. In this cohort, survival was indistinguishable between HHT and OHT recipients in the first four years. Thus, HHT might be a viable alternative to durable mechanical circulatory assist particularly with size mismatched grafts or for patients with refractory pulmonary hypertension.

Donor risk analysis and validation in heart transplants: a single-centre experience

OBJECTIVES

A heart transplant (Htx) remains the gold standard treatment for patients with advanced heart failure. Considering the limited availability of organs, donor risk scores might improve organ selection and allocation. The objective of the study was to compare United Network for Organ Sharing, RADIAL and Eurotransplant scoring models in calculating post-Htx outcomes in an Italian Htx population.

METHODS

Between January 2000 and December 2017, a total of 461 adult patients underwent Htxs. United Network for Organ Sharing, RADIAL and Eurotransplant scores were calculated. Clinical features and donor risk scores were tested to identify preoperative, intraoperative and postoperative risk variables and eventually validate the scores on our population.

RESULTS

Early graft failure was detected in 16.1% (74/461). Post-Htx extracorporeal life support was used in 11.1% (51/461). Of the donor-related factors, the use of noradrenaline (P = 0.015) negatively influenced early outcomes, whereas an ischaemic time >240 min (P = 0.037) influenced early graft failure occurrence. The Eurotransplant donor score did not impact outcomes; the RADIAL score significantly influenced both early and late mortality; and the United Network for Organ Sharing score influenced only late mortality. On the multivariable analysis, after adjustment of scores per cohort, noradrenaline infusion was the main independent predictor of in-hospital mortality for the donors, whereas age of the recipient [odds ratio (OR) 1.003, 1.003-1.081; P = 0.032] and use of preoperative extracorporeal membrane oxygenation (OR 3.320, 1.124-9.805; P = 0.030) were the main independent predictors for the recipients.

CONCLUSIONS

None of the validated donor scoring systems fully behave as reliable predictors of transplant outcomes. According to our 'local only' graft selection, specific donor and recipient risk variables should be monitored in order to predict early and late outcomes satisfactorily.

Prolonged Cold Ischemia Time in Mouse Heart Transplantation Using Supercooling Preservation

BACKGROUND

Supercooling preservation techniques store a donor organ below 0°C without freezing. This has great advantages in inhibiting metabolism and preserving the organ in comparison to conventional preservation at 4°C. We developed a novel supercooling technique using a liquid cooling apparatus and novel preservation and perfusion solutions. The purpose of this study was to evaluate the preservation effect of our supercooling preservation technique in a mouse heart transplantation model.

METHODS

Syngeneic heterotopic heart transplantation was performed in 3 groups of mice: (1) the nonpreservation group, in which the cardiac grafts were transplanted immediately after retrieval; (2) the conventional University of Wisconsin (UW) group, in which the cardiac grafts were stored in UW solution at 4°C for different periods of time; and (3) the supercooling group, in which the cardiac grafts were stored in a novel supercooling preservation solution at -8°C for different periods of time. The maximal preservation time was investigated. Twenty-four-hour sample data were collected and analyzed to compare supercooling preservation to conventional UW preservation.

RESULTS

Our technique yielded a stable -8°C supercooling state. Cardiac graft revival was successfully achieved after supercooling preservation for 144 hours, and long-term survival was observed after supercooling preservation for 96 hours. Posttransplant outcomes, including myocardial ischemia-reperfusion injury, oxidative stress-related damage, and myocardial cell apoptosis, were improved in comparison to conventional 4°C UW preservation.

CONCLUSIONS

Supercooling heart preservation at -8°C greatly prolonged the preservation time and improved the posttransplant outcomes in comparison to conventional 4°C UW preservation. Supercooling preservation is a promising technique for organ preservation.

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.

Predicted heart mass is the optimal metric for size match in heart transplantation

BACKGROUND

Donor-recipient size match is traditionally assessed by body weight. We assessed the ability of 5 size match metrics-predicted heart mass (PHM), weight, height, body mass index (BMI) and body surface area (BSA)-to predict 1-year mortality after heart transplant and to assess the effect of size match on donor heart turn down for size.

METHODS

The study cohort comprised 19,168 adult heart transplant recipients in the United Network for Organ Sharing registry between 2007 and 2016. Each size match metric was divided into 7 equally sized groups using the donor-recipient ratio for each metric. Single and multivariable Cox proportional hazard models for mortality 1 year after transplant were constructed.

RESULTS

Recipients in the severely (donor-recipient PHM ratio 0.54-0.86) undersized group for PHM experienced increased mortality, with a hazard ratio of 1.34 (95% confidence interval, 1.13-1.59; p < 0.001). There was no increased risk of death at 1 year if donors were undersized for weight, height, BMI, or BSA. We found that 32% of heart offers turned down for donor size would be acceptable using a PHM threshold of 0.86 or greater and that 14% of offers accepted (most of which are female donor to male recipient) were below this threshold.

CONCLUSIONS

PHM is the optimal donor-recipient size match metric for prediction of mortality after heart transplant. Many offers turned down for donor size were above the threshold for adequacy of size match by PHM identified, and thus, the use of PHM could improve donor heart utilization and post-transplant survival.