Abstract 18615: Subclinical Thyroid Dysfunction, Rather than Low-T3 Syndrome, is an Independent Predictor of Adverse Cardiac Events in Patients with Acute Decompensated Heart Failure

Abstract

Background: Altered thyroid hormone metabolism characterized by low triiodothyronine (T3) levels is a common finding in patients with severe systemic diseases, called low T3 syndrome (LT3-S). Additionally, subclinical thyroid dysfunction, defined as abnormal thyroid-stimulation hormone (TSH) and normal thyroxine (T4) levels, causes left ventricular dysfunction. However, the prevalence and prognostic impact of LT3-S and subclinical thyroid dysfunction in patients with acute decompensated heart failure (ADHF) have not been investigated. Methods: We examined consecutive 287 patients with ADHF who received thyroid function tests and no thyroid medications at admission (age 69±15 years, 166 male). Thyroid dysfunction was defined as follows: LT3-S as free T3< 4.0 pmol/L; euthyroidism as TSH of 0.45 to 4.49 mIU/L; subclinical hypothyroidism (Sc-hypo) as TSH of 4.5 to 19.9 mIU/L; subclinical hyperthyroidism (Sc-hyper) as TSH< 0.45mIU/L with normal free T4 levels for the last two. We sought to investigate the impact of the indices of thyroid function and the thyroid disorders above to predict cardiac death and re-hospitalization for heart failure after discharge. Results: At admission for ADHF, 155 patients (54%) showed LT3-S, and 62 (22%) Sc-hypo, and 5 (2%) Sc-hyper, and 196 (68%) euthyroidism. Cox proportional hazards model analysis revealed that TSH and fT4, not fT3, were independent predictors of adverse cardiac events among variables including age, sex, estimated glomerular filtration rate, left ventricular ejection fraction and B-type natriuretic peptide. Indeed, Sc-hypo was an independent predictor (HR 2.21, 95% CI 1.41-3.43, p< 0.001), whereas LT3-S and SC-hyper was not (p = 0.49 and 0.24, respectively). Conclusion: Although LT3-S was observed in about half of ADHF patients, the presence of LT3-S did not indicate poor prognosis after discharge. Meanwhile, Sc-hypo at admission was an independent predictor of adverse cardiac events in ADHF patients.