BACKGROUND: Cardiopulmonary exercise test (CPT) has a prominent value in 
assessing clinical severity in chronic heart failure (HF) patients. Reduced free 
triiodothyronine (fT3) plasma level is associated with a more severe disease and 
prognosis. The aim of this study was to evaluate the relationship between low 
fT3 plasma level and reduced exercise capacity in chronic HF, and to determine 
the influence of a low T3 status in subsets of patients with different 
functional impairment.
METHODS AND RESULTS: 240 HF patients (79% males; age 62 ± 12 years, mean ± 
standard deviation; left ventricular ejection fraction, EF, 30 ± 9%) underwent a 
CPT, clinical and neurohormonal characterization (assay for plasma brain 
natriuretic peptide, BNP, norepinephrine, aldosterone, renin activity, fT3, free 
T4, thyroid-stimulating hormone). At multivariate analysis in the whole 
population, age, gender and BNP level were independently associated with peak 
VO2, whereas in patients with severe functional impairment (peak VO2 < 14 
ml/min/kg) fT3 resulted independently related to peak VO2, together with gender 
and BNP. When patients with peak VO2 < 14 ml/min/kg were divided according to 
fT3 levels, patients with low T3 syndrome showed reduced exercise capacity and 
worse ventilatory efficiency.
CONCLUSIONS: BNP and fT3 are independently associated with exercise capacity in 
severely compromised HF patients.