Low T3 Syndrome Is Associated With High Mortality in Hospitalized Patients With Heart Failure

We aimed to clarify the prognosis and pathophysiological parameters of low T3 syndrome in patients with heart failure (HF).

Hospitalized patients with HF and euthyroidism (n = 911) were divided into 2 groups on the basis of free triiodothyronine (FT3) serum levels: the normal FT3 group (FT3 ≥2.3 pg/mL; n = 590; 64.8%) and the low FT3 group (FT3 <2.3 pg/mL; n = 321; 35.2%). We compared post-discharge cardiac and all-cause mortality by means of Kaplan-Meier analysis and Cox proportional hazard analysis, and the parameters of echocardiography and cardiopulmonary exercise testing by means of Student t test. In the follow-up period of median 991 (interquartile range 534-1659) days, there were 193 all-cause deaths, including 88 cardiac deaths. Cardiac and all-cause mortality were higher in the low FT3 group (log-rank P < .01). Low FT3 was a predictor of cardiac death (hazard ratio 1.926, 95% confidence interval [CI] 1.268-2.927; P = .002) and all-cause death (hazard ratio 2.304, 95% CI 1.736-3.058; P < .001). Although left ventricular ejection fraction was similar between the groups, the low FT3 group showed lower peak VO₂ (13.6 ± 4.6 vs 16.6 ± 4.4 mL·kg^-1·min,^-oneP < .001) and higher VE/VCO₂ slope (36.5 ± 8.2 vs 33.0 ± 7.5; P = .001).

Low T3 syndrome in patients with HF is associated with higher cardiac and all cause-mortality.