We sought to explore the use of triiodothyronine (T₃) concentrations as an adjunct to clinical and functional parameters when estimating prognosis in patients with chronic heart failure.

We enrolled 281 patients with postischemic (n = 153) or nonischemic (n = 128) dilated cardiomyopathy. Total and free T₃ concentrations, and traditional clinical and functional cardiac parameters, were measured 2 to 5 days after hospital admission. A multivariate model was utilized to predict all-cause and cardiac mortality.

All-cause mortality was 23% (n = 64) after a mean (±SD) of 12 ± 7 months of follow-up; 47 (73%) of the patients died from cardiac causes. The mean ejection fraction was lower in those patients who died than in those who survived (26% ± 8% vs. 31% ± 8%, P < 0.001), as were levels of total T₃ (1.0 ± 0.4 nmol/L vs. 1.3 ± 0.3 nmol/L, P < 0.001) and free T₃ (3.2 ± 1.4 pmol/L vs. 3.7 ± 1.0 pmol/L, P < 0.001). In a multivariate model, ejection fraction (odds ratio [OR] = 2.0 per 10% decrease; 95% confidence interval [CI]: 1.4 to 2.8 per 10% decrease; P < 0.001) and total T₃ level (OR = 0.3 per 1-nmol/L increase; 95% CI: 0.1 to 0.5 per 1-nmol/L increase; P < 0.001) were the only independent predictors of all-cause mortality. In an alternative model using free T₃ levels, ejection fraction (OR = 1.9; 95% CI: 1.4 to 2.7; P < 0.001) and free T₃ level (OR = 0.6 per 1 pmol/L; 95% CI: 0.5 to 0.8 per 1 pmol/L; P <0.02) were associated with all-cause mortality. When we considered cardiac mortality alone, male sex (OR = 3.5; 95% CI: 1.7 to 13; P < 0.04), ejection fraction (OR = 1.7; 95% CI: 1.2 to 2.5; P < 0.006), and total T₃ level (OR = 0.3; 95% CI: 0.2 to 0.7; P < 0.002) were independent predictors with the multivariate model.

Low T₃ levels are an independent predictor of mortality in patients with chronic heart failure, adding prognostic information to conventional clinical and functional cardiac parameters.