Matching Donor and Recipient Size in Pediatric Heart Transplantation

Individual Association of Predicted Left and Right Ventricular Mass Ratios With Survival After Heart Transplantation: A UNOS Database Analysis

BACKGROUND

Predicted heart mass (PHM) ratio is a commonly used metric for donor-to-recipient size matching that has been associated with survival after heart transplantation (HTx). PHM represents a sum of two separate statistical models for predicted left ventricular mass (PLVM) and predicted right ventricular mass (PRVM); however, their individual contributions have not been sufficiently studied. We sought to assess the association of donor-to-recipient PLVM (PLVMR) and PRVM ratios (PRVMR) with overall posttransplant survival individually.

METHODS

Adult heart transplant recipients from 2005 to 2021 were queried from the UNOS database. A three-dimensional tensor product spline model assessed the association of PLVMR and PRVMR with survival simultaneously on a continuous distribution. Subsequently, PLVMR and PRVMR were explored individually using individual restricted cubic spline models.

RESULTS

A total of 25 549 patients were analyzed. Of these, female recipients comprised 26.7% (n = 6818), and the median age was 56 [IQR 46-63] years. In the three-dimensional restricted cubic spline (3D-RCS) model, PLVMR and PRVMR were significantly associated with survival (p value: overall = 0.002, PLVMR = 0.0006, PRVMR = 0.0006, PLVMR*PRVMR = 0.0002). When analyzed with two-dimensional restricted cubic spline (2D-RCS) models, PLVMR was not associated with survival (p = 0.59), while PRVMR retained its significant association (p = 0.04).

CONCLUSION

While both PLVMR and PRVMR appear to be associated with posttransplant survival, the effect of PRVMR might be disproportionately high as PRVM makes up a much smaller fraction of PHM than PLVM.

Metrics for size-matching in paediatric cardiac transplantation: A narrative review

Several metrics exist for matching the size of donor to recipient in paediatric cardiac transplantation. Different centres employ different metrics for size-matching to determine the viability of donor hearts. Inconsistent evidence exists, with limited consensus as to the metric for size-matching that is most predictive of outcomes after cardiac transplantation. Furthermore, any metric must function within the tight timeline available for the assessment of the suitability of the donor. At the time of the writing of this paper, the most commonly used metric for size-matching in paediatric cardiac transplantation is the donor-to-recipient body weight ratio. In this article, we review published literature evaluating commonly used metrics for size-matching in paediatric cardiac transplantation, including weight, height, body surface area, and imaging parameters.

De Novo and Progressive Pulmonary Vein Stenosis Following Pediatric Heart Transplantation: A Multicenter Retrospective Study

BACKGROUND

Pulmonary vein stenosis (PVS) is a rare condition in which neointimal proliferation leads to venous and arterial hypertension. Little is known about PVS after heart transplant (HTx) in children. We sought to describe the characteristics and outcomes of children who develop PVS after HTx.

METHODS

We performed a retrospective review of patients ≤18 years old who underwent HTx at two HTx centers between April 2012 and October 2023. Patients with PVS were identified via database queries. Cardiac diagnosis, PVS location and extent, and outcomes were recorded.

RESULTS

Over 11.5 years, 422 patients underwent HTx across both centers. Nineteen patients with PVS (10 male) were identified, 15 with de novo PVS. Sixteen had underlying congenital heart disease (CHD), two with anomalous pulmonary venous return. PVS was diagnosed at a median of 2 months (range 2 weeks to 14 years) after HTx. At time of initial diagnosis, 13 patients had one-vessel PVS. At final follow-up, 7/19 (37%) had increases in the number of vessels involved. Six patients underwent surgery, and nine patients had stent or balloon angioplasty. Two patients were treated for pulmonary hypertension following PVS diagnosis. Three patients died from right heart failure secondary to PVS.

CONCLUSIONS

This is the largest study to describe the characteristics of post-HTx PVS in children. PVS occurs in 4.5% of HTx, and underlying CHD is a strong risk factor. Multiple vessels can be involved and may require catheter-based or surgical intervention. Clinicians must be vigilant in monitoring the development of PVS in this population.

Review of pediatric combined heart-liver transplantation: A roadmap to success

BACKGROUND

Combined heart-liver transplantation (CHLT) is a promising technique to address end stage organ failure in patients with concomitant heart failure and chronic liver disease. While most experience with CHLT has involved adult patients, the expanding population of children born with univentricular congenital heart disease who underwent the Fontan procedure and develop Fontan-associated liver disease (FALD) has emerged as a growing indication for pediatric CHLT.

METHODS

Currently, CHLT is performed at a select subset of experienced transplant centers, especially in the pediatric population.

RESULTS

While technically demanding, CHLT may offer survival benefit when compared to heart transplant alone with decreased rejection of both synchronous allografts and equivalent outcomes with respect to waitlist time and post-operative complications. Limitations in the technique can be attributed to need for an appropriate multidisciplinary care center, challenges with donor organ availability and allocation, and the complexity associated with patient selection and peri-operative management.

CONCLUSION

In this review, we summarize the history of CHLT, discuss patient selection, and highlight key facets of peri-operative care in the pediatric population.

Predicted heart mass based on ideal body weight for donor-to-recipient size matching

BACKGROUND

Predicted heart mass (PHM) is a commonly used tool for donor-to-recipient size matching. However, incorporating body weight as part of PHM can be considered problematic given its high variability, and low metabolic nature of fat. We sought to assess whether substituting the actual donor and recipient weight with the ideal body weight (IBW) would affect the association of donor-to-recipient PHM ratio with 1-year and overall survival after heart transplantation.

METHODS

The United Network for Organ Sharing (UNOS) database was queried for adult patients who received a primary heart transplant between January 2000 and September 2021.

RESULTS

Both PHM and ideal PHM (IPHM) ratios were associated with one-year (PHM: p = .003; IPHM: p = .0007) and overall (PHM: p = .02; IPHM: p = .02) survival. In the continuous analysis with restricted cubic splines, both PHM (p = .0003) and IPHM (p = .00001) were associated with relative hazards of death.

CONCLUSION

IPHM is significantly associated with post-transplant survival and may be a useful compliment to PHM.

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.