Aims:
Cardiac transplant recipients often suffer from diabetes mellitus (DM) but its influence on graft failure and post-transplant mortality remains unknown. The aim of this study was to investigate the long-term effects of DM in patients after heart transplantation (HTX).

Methods:
This study included a total of 377 adult patients who received HTX at Heidelberg Heart Center between 01/01/2000 and 01/10/2016. HTX recipients were stratified by diagnosis of DM at the time of HTX. Patients with DM were further subdivided by glycated hemoglobin (HbA1c ≥ 6.5%). Analysis included donor and recipient data, immunosuppressive drugs, concomitant medications, post-transplant mortality, and causes of death. Five-year post-transplant mortality was further assessed by multivariate analysis (Cox regression) and Kaplan–Meier estimator.

Results:
About one-third of all HTX recipients had DM (122 of 377 [32.4%]). Patients with DM showed an increased 5-year post-transplant mortality (41.0% versus 29.8%; P = 0.031) and had a higher percentage of death due to graft failure (14.8% versus 7.8%; P = 0.037). Multivariate analysis showed DM (HR: 1.54; 95% CI: 1.04–2.29; P = 0.031) as an independent risk factor for 5-year mortality after HTX. Stratified by glycated hemoglobin, Kaplan–Meier analysis showed a significantly better 5-year post-transplant survival of patients with DM and a HbA1c < 6.5% than patients with DM and a HbA1c ≥ 6.5% (69.7% versus 46.4%; P = 0.007) emphasizing the clinical relevance of a well-controlled DM in HTX recipients.

Conclusions:
DM in HTX recipients is associated with higher graft failure and increased 5-year post-transplant mortality.

Keywords: diabetes mellitus, graft failure, HbA1c, heart transplantation, mortality, survival