Oversized donor heart transplantation-clinical experience with an underestimated problem

Transthoracic echocardiography is a simple tool for size matching in cardiac xenotransplantation

BACKGROUND

Preoperative size matching is essential for both allogeneic and xenogeneic heart transplantation. In preclinical pig-to-baboon xenotransplantation experiments, porcine donor organs are usually matched to recipients by using indirect parameters, such as age and total body weight. For clinical use of xenotransplantation, a more precise method of size measurement would be desirable to guarantee a "perfect match." Here, we investigated the use of transthoracic echocardiography (TTE) and described a new method to estimate organ size prior to xenotransplantation.

METHODS

Hearts from n = 17 genetically modified piglets were analyzed by TTE and total heart weight (THW) was measured prior to xenotransplantation into baboons between March 2018 and April 2022. Left ventricular (LV) mass was calculated according to the previously published method by Devereux et al. and a newly adapted formula. Hearts from n = 5 sibling piglets served as controls for the determination of relative LV and right ventricular (RV) mass. After explantation, THW and LV and RV mass were measured.

RESULTS

THW correlated significantly with donor age and total body weight. The strongest correlation was found between THW and LV mass calculated by TTE. Compared to necropsy data of the control piglets, the Devereux formula underestimated both absolute and relative LV mass, whereas the adapted formula yielded better results. Combining the adapted formula and the relative LV mass data, THW can be predicted with TTE.

CONCLUSIONS

We demonstrate reliable LV mass estimation by TTE for size matching prior to xenotransplantation. An adapted formula provides more accurate results of LV mass estimation than the generally used Devereux formula in the xenotransplantation setting. TTE measurement of LV mass is superior for the prediction of porcine heart sizes compared to conventional parameters such as age and total body weight.

Heart Transplantation

Heart transplantation (HTx) remains the last therapeutic resort for patients with advanced heart failure. The present work is a clinically focused review discussing current issues in heart transplantation. Several factors have been associated with the outcome of HTx, such as ABO and HLA compatibility, graft size, ischemic time, age, infections, and the cause of death, as well as imaging and laboratory tests. In 2018, UNOS changed the organ allocation policy for HTx. The aim of this change was to prioritize patients with a more severe clinical condition resulting in a reduction in mortality of people on the waiting list. Advanced heart failure and resistant angina are among the main indications of HTx, whereas active infection, peripheral vascular disease, malignancies, and increased body mass index (BMI) are important contraindications. The main complications of HTx include graft rejection, graft angiopathy, primary graft failure, infection, neoplasms, and retransplantation. Recent advances in the field of HTx include the first two porcine-to-human xenotransplantations, the inclusion of hepatitis C donors, donation after circulatory death, novel monitoring for acute cellular rejection and antibody-mediated rejection, and advances in donor heart preservation and transportation. Lastly, novel immunosuppression therapies such as daratumumab, belatacept, IL 6 directed therapy, and IgG endopeptidase have shown promising results.

Increasing donor-recipient weight mismatch in infant heart transplantation is associated with shorter waitlist duration and no increased morbidity or mortality

OBJECTIVES

Infants awaiting paediatric heart transplantation (PHT) experience long waitlist duration and high mortality due to donor shortage. Using the United Network for Organ Sharing database, we explored if increasing donor-recipient weight ratio (DRWR) >2.0 (recommended cutoff) was associated with adverse outcomes.

METHODS

Between 2007 and 2020, 1392 infants received PHT. We divided cohort into 3 groups: A (DRWR ≤1.0, n = 239, 17%), B (DRWR 1.0-2.0, n = 947, 68%), C (DRWR >2.0, n = 206, 15%). Group characteristics and PHT outcomes were analysed.

RESULTS

DRWR ranged between 0.5 and 4.1. Underlying pathology (congenital versus cardiomyopathy), gender, race, renal function and mechanical circulatory support were comparable between groups. Group C patients were more likely to be ventilated, to receive ABO blood group (ABO)-incompatible heart and to have longer donor ischaemic time. Waitlist duration was significantly shorter for group C (33 vs 50 days, P < 0.1). Early outcomes for groups A, B and C were the following (respectively): operative death (6%, 4%, 3%, P = 0.29), primary graft dysfunction (5%, 3%, 3%, P = 0.30), renal failure (10%, 7%, 7%, P = 0.42) and stroke (3%, 4%, 1%, P = 0.36). The DRWR group was not associated with operative death in either congenital (odds ratio (OR) = 0.819, 95% confidence interval (CI) = 0.523-1.282) or cardiomyopathy (OR = 1.221, 95% CI = 0.780-1.912) patients and only significant factor was pre-PHT extracorporeal membrane oxygenation (OR = 4.400, 95% CI = 2.761-7.010). Additionally, survival at 1 year (87%, 87%, 85%, P = 0.80) and 5 years (76%, 78%, 77%, P = 0.80) was comparable between the DRWR groups.

CONCLUSIONS

Infants who received PHT with DRWR >2.0, up to 4.1, experienced shorter waitlist duration with no demonstrable increase in peri-transplant complications, operative or late mortality. Historic practice to avoid DRWR > 2.0 due to complications (e.g. hypertension-related stroke, graft dysfunction, death) is not currently supported in infants and stretching DRWR acceptance criteria would decrease PHT waitlist duration and potentially improve waitlist complications and mortality.

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 2-year postoperative left heart function in marginal donor heart recipients assessing by speckle tracking echocardiography

This study analyzed the differences and explored the donor/recipient factors between marginal and standard donor heart recipients after heart transplantation (HT) by speckle tracking echocardiography (STE). Seventy-two HT patients were enrolled: 25 standard and 47 marginal donor heart recipients. Thirty HT patients completed 2-year continuous follow-up (1, 6, 12, 24 months). Thirty healthy volunteers were controls. STE was used to track the strain characteristics of the left ventricle and atrium for detecting early changes in marginal donor heart recipients, including left ventricular global longitudinal, circumferential and radial strain (LVGLS, LVGCS, LVGRS) and left atrial strain in systole (LAS-S) and late diastole (LAS-A). The perioperative parameters were similar between the standard and marginal groups. No significant differences were found in left heart size, systolic and diastolic function parameters. Left ventricular systolic strain (LVGLS, LVGCS, LVGRS) and systolic and late diastolic left atrial strain (LAS-S, LAS-A) were lower in the HT recipients than the control group (P < 0.05), but there was no difference between the marginal and standard groups (P > 0.05). LVGLS, LVGCS, and LAS-S were low in the marginal group 1 month after surgery but recovered gradually at 6 months. The patients with donor/recipient body weight ratio < 0.8 group had lower LVGLS and LAS-S. STE showed no significant difference between marginal and standard donor recipients. The LVGLS and LAS-S were lower in those with a smaller donor/recipient body weight ratio. The cardiac function of HT patients was lower in the early postoperative period but gradually recovered over time.

Influence of Body Mass Index in Donor-Recipient Size Mismatch in Pediatric Heart Transplantation

BACKGROUND

Body weight is the traditional metric for matching donor and recipient size for pediatric heart transplantation (pHT). We hypothesized that mismatch in body mass index (BMI) or body surface area (BSA) rather than weight is better associated with outcomes of transplantation and therefore should be used for donor-recipient size matching.

METHODS

Analysis of the United Network for Organ Sharing database limited to pHT recipients was performed. Donor and recipient mismatch groups were created for weight, BMI, and BSA ratios. Differences in recipient characteristics between each cohort and the impact of mismatch on outcomes were statistically analyzed.

RESULTS

A total of 4,465 patients were included in the analysis of which 43% had congenital heart disease (CHD). There were significant differences in patient characteristics by matching, independent of the matching parameter. Multivariable regression analysis showed that a low donor-recipient BMI ratio (compared to normal) (CHD OR 1.70; non-CHD 2.78) was a predictor of one-year mortality (all P < .001) in both CHD and non-CHD cohorts. Low BMI ratio was also associated with worse long-term survival in non-CHD groups, but not in the CHD cohort. Weight and BSA ratio did not predict one year or long-term survival.

CONCLUSION

The use of low BMI donors compared to recipient may predict poor early and long-term survival and therefore should be avoided in pHT. The use of BMI matching may improve donor-recipient matching in pHT.