Seese L, Morell VO, Viegas M, Keebler M, Hickey G, Wang Y, Kilic A.Ann Thorac Surg. 2021 Jun;111(6):2033-2040. doi: 10.1016/j.athoracsur.2020.05.154. Epub 2020 Jul 29.PMID: 32738222
Take Home Points:
- The authors created a 13-point risk score predictive of mortality within 1 year of orthotopic heart transplantation, of possible use in informing patient selection for these types of transplants.
- The risk score, based on a North American/ USA cohort, was as follows:
- 0 points predicted a 1 year mortality of 14.6% and 13 points 49.9%, with a graduation seen in between.
Commentary by Dr. Simon MacDonald (London, UK), section editor of ACHD Journal Watch:
Advances in congenital heart disease treatment have allowed a greater number of congenital patients to survive to adulthood. Many require advanced heart failure treatment and consideration of heart transplantation. This can be orthotopic (where the recipients heart is removed for the donor heart ) or heterotopic (where the donor heart assists the failing recipient heart in a ‘piggy-back’ arrangement). The authors studied orthotopic transplantation, looking to derive and validate a risk score for 1 year mortality in ACHD patients.
They studied patients ≥18 years of age with congenital heart disease undergoing orthotopic heart transplantation between 1987 and 2018, within the United Network for Organ Sharing (UNOS) registry. This is a United States organisation that manages the US organ transplant system. Patients who received heterotopic, redo transplantation or multiorgan transplant (including heart-lung transplants) were excluded.
They split the study population into 2 groups; a derivation cohort of 66% of the patients and a validation cohort of the remaining 34% to test the score. A secondary outcome was risk score stratified rates of major morbidities and hospital length of stay. It was not stated how this randomisation occurred.
The UNOS registry contains 542 variables and they were evaluated using univariate logistic regression in the derivation cohort, adjusting for transplant year and average volume of transplant at each centre.
They used 1388 ACHD OHT patients, mean age 34.6≥13.0 years and women 38%. The majority of patients were white (83.2%). In terms of donors, mean age was 27.6≥11.3yrs, with traumatic injury the most common donor mechanism of death (50%, n=692).
Initial exploratory logistic regression analysis identified 26 covariates for 1 year mortality in the derivation cohort. Final multivariable model included 8 variables (p<0.05); greater than 30 years of age, pretransplant mechanical ventilation, pretransplant dialysis, serum bilirubin≥ 2.4mg/dl, male sex of donor, and later transplant era (2000-2010) (table 2 below) before they settled on the risk factors in table 3.
The authors comment that many ACHD patients have unique challenges such as need for complex vascular reconstruction, elevated panel reactive antibodies and ABO blood group sensitization and that, when listed for OHT, they are less likely to receive a transplant than with a patient with acquired heart failure.
The tool seemed predictive of 1 year mortality and adverse outcomes, with a graded increase in predicted and observed rates of 1 year mortality as the score increased from 0 to 13. Patients with a score≥4 had substantially higher risks of mortality at 30 days, 90 days and 1 year. Pretransplant dialysis dependence and mechanical ventilation conferred the highest risk.
There was not enough data to do subgroup analysis on the different types of ACHD needing transplant, nor was the numbers and types of simple to complex ACHD seen stated and the numbers and types of prior operation stated. Missing data in the transplant dataset was a problem in this regard. The authors state that failed Fontan palliation and single ventricle anatomy predicted OHT mortality with increased graft failure, infection and bleeding in an earlier study. The study was retrospective and only based in a North American cohort. Testing in European and Eastern cohorts would have given further confidence for the score in other populations. The Eisenmenger population, who largely get heart-lung transplantation, would also have been excluded from the study.
The risk score may help in the pretransplant assessment of ACHD patients regarding patient selection and provides a step forward in evaluating complex ACHD patients, suggesting future multi-centre studies of selection criteria.