Perioperative Low Tetraiodothyronine Levels and Adverse Outcomes After Heart Transplantation: A Retrospective, Observational Study

Objectives: Thyroid dysfunction has been shown to be associated with increased all-cause mortality and severity of chronic heart failure in critical illness and severe cardiac diseases. The present study was conducted to ascertain the relationship between perioperative free triiodothyronine and free tetraiodothyronine (fT4) levels and postoperative adverse outcomes after heart transplantation (HTX).

Design: Retrospective, observational study.

Setting: Single-center study in a quaternary care university clinical center.

Participants: The study comprised adult patients who underwent HTX between 2015 and 2019 and had at least 1 perioperative thyroid hormone laboratory test on the day of surgery or in the 24 hours before/after the procedure (free triiodothyronine, fT4, and thyroid-stimulating hormone).

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 and 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. An independent association was found between fT4 and PGD (odds ratio 6.49; 95% confidence interval 2.26-18.61; p = 0.001), with adjusted multivariate Cox regression models.

Conclusion: The perioperative fT4 level could be a prognostic marker of adverse outcomes in HTX. The authors suggest appropriate perioperative monitoring of fT4 levels. Additional research is warranted to examine the optimal timing, dosage, and method of replacement.