BACKGROUND: We aimed to clarify the prognosis and pathophysiological parameters of low T3 syndrome in patients with heart failure (HF). METHODS AND RESULTS: 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). CONCLUSION: Low T3 syndrome in patients with HF is associated with higher cardiac and all cause-mortality.
BACKGROUND: We aimed to clarify the prognosis and pathophysiological parameters of low T3 syndrome in patients with heart failure (HF). METHODS AND RESULTS: 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). CONCLUSION:Low T3 syndrome in patients with HF is associated with higher cardiac and all cause-mortality.