Background: Homeostasis of thyroid hormones has significant effects on
the cardiovascular system. The aim of this study was to investigate the
association between free triiodothyronine (FT3) and adverse cardiovascular events
in patients with acute coronary syndrome (ACS) who were undergoing percutaneous
coronary intervention (PCI). Methods: A total of 1701 patients with ACS
undergoing PCI were included in this study. All patients were divided into three
groups according to the tertiles of FT3 level: the lowest tertile (FT3 4.51
pmol/L), the middle tertile (4.51 pmol/L FT3 4.89 pmol/L) and the
highest tertile group (FT3 4.89 pmol/L). The primary study endpoint was a
composite of major adverse cardiovascular events (MACE), which included all-cause
death, ischemic stroke, myocardial infarction, or unplanned repeat
revascularization. Results: During a median follow-up period of 927
days, 349 patients had at least one event. Compared with patients with the
highest tertile, those with the lowest tertile had a significantly higher
incidence of MACE, all-cause death, MI, ischemic stroke and repeat
revascularization (all p values 0.05). In the multivariate Cox
regression analysis, the middle tertile had similar risk of MACE (HR = 0.986,
95% CI 0.728–1.336, p = 0.929) as the highest tertile, but the
patients with the lowest tertile had a 92.9% higher risk of MACE (HR = 1.929,
95% CI 1.467–2.535, p 0.001). There was a non-linear relationship
between FT3 and MACE and unplanned repeat revascularization (all p
values for non-linear association 0.001). Adding the tertiles of FT3 level
into the baseline model yielded a significant improvement in discrimination for
predicting MACE (AUC = 0.013, p = 0.025).
Conclusions: A significantly reduced FT3 level was independently
associated with a worse prognosis in patients with ACS undergoing PCI.