Orthotopic Cardiac Transplantation (OCTx) is the gold standard treatment for advanced heart failure (AHF).1 Globally, the number of patients on OCTx transplant waitlists is growing, largely owing to improved overall survival in heart failure (HF).2 In the United Kingdom (UK), routine-listed patients have an average waitlist time of between 18 and 24 months.3 Efforts are being made to reduce waitlist times, such as through increasing usage of donor hearts following circulatory death (DCD); 237 UK OCTx procedures were performed between March 2023-2024.4 Currently, successful OCTx results in a median survival of between 11 and 13 years.5

Both patients and care-providers face uncertainty with regards to how long patients will remain on the waitlist until an appropriate organ offer is made. Predicting the time to transplant from being waitlisted is a difficult entity, with understandable associated apprehension.6 There are numerous factors that can impact whether a patient will receive an available donor organ. In the UK, patients undergo central waitlist allocation from routine to super-urgent; correspondingly shorter wait-times exist for those patients on the super-urgent list.7 Aside from the allocation status, recipient factors can influence the time taken to undergo a transplant offer. Recognised factors include age, gender, the presence and extent of human leukocyte antigens (HLA, %), blood group (BG), body mass index (BMI) and utility of pre-transplant mechanical circulatory support. Additionally, waitlist times vary upon a transplant centre-upon-centre basis.7

Currently, the UK National Health Service Blood and Transplant (NHSBT) service provide a predictive tool, using data from the cardiothoracic transplant centres nationally, that gives a likelihood of a recipient receiving a heart transplant from the various waitlist priorities at different timepoints (3-, 6-, 9- and 12 month timepoints per cardiothoracic transplant centre).8 The variables included in the NHSBT model include: previous registration [on OCTx waitlist], reason for urgent listing (for example owing to urgent intravenous inotrope use or owing to complications with long term ventricular assist device [VAD]), BG, primary disease, recipient weight and height, recipient cytomegalovirus (CMV) positivity and presence of cerebrovascular disease. However, the predictive tool does not include important variables, such as age or HLA%, that are known to influence likelihood of receiving a transplant. Additionally, it includes recipient CMV status, a variable that should not theoretically alter likelihood of receiving a transplant.

As one of the largest cardiothoracic transplant centres in the UK, Harefield Hospital (Royal Brompton and Harefield Hospitals, part of Guy’s and St Thomas’ NHS Foundation Trust) conducts approximately 40 OCTx procedures annually. In this study, we sought to ascertain if development of a predictive model, incorporating HLA with known prognostic risk-stratification variables, could accurately predict probability of OCTx at 3-, 6-, 9- and 12-month timeframes.