Perioperative low tetraiodothyronine (T4) levels and adverse outcomes after heart transplantation: A retrospective observational study

ABSTRACT Objective(s) Thyroid dysfunction have shown to be associated with increased all-cause of mortality and increased severity of chronic heart failure in critical illness and severe cardiac diseases. We conducted our study to ascertain the relationship between perioperative free triiodothyronine (fT3) and free tetraiodothyronine (fT4) levels and postoperative adverse outcomes after heart transplantation. Design Retrospective observational study. Setting Single center study in a quaternary care university clinical center. Participants Adult patients who underwent heart transplantation (HTX) between 2015 and 2019 and had at least one perioperative thyroid hormone laboratory test on the day of surgery, or in the 24 hours before/after the procedure (fT3, fT4 and TSH) were included. Interventions No interventions were applied. Measurements and Main Results The primary outcome was primary graft dysfunction (PGD) defined by the consensus conference of The International Society for Heart & Lung Transplantation. A total of 151 patients were included in the final analyses. Twenty-nine (19.2%) patients had PGD. Fourteen (9.3%) patients had low fT4 levels. We found an independent association between fT4 and PGD (OR: 6.49; 95% CI: 2.26-18.61; p=0.001) with adjusted multivariate Cox regression models. Conclusion Perioperative fT4 level could be a prognostic marker of adverse outcomes in HTX. We suggest appropriate peri-operative monitoring of fT4 levels. To examine the optimal timing, dosage and the way of replacement warrant further research.