Thyroid dysfunction only weakly predictive of survival in chronic heart failure

While thyroid dysfunction does worsen survival among patients with chronic heart failure (CHF), there are other stronger predictive factors of adverse outcomes in these patients, a new study has shown.

Researchers retrospectively assessed 4,492 heart failure patients, in whom thyroid function was evaluated according to levels of the thyroid-stimulating hormone (TSH) and free thyroxine. The primary outcome of interest was all-cause mortality, while a secondary outcome was the composite between mortality or hospitalization with heart failure.

Over a median follow-up duration of 4.6 years, a total of 2,879 participants died, yielding a mortality rate of 58 percent. Unadjusted analyses found that participants with either hypo- or hyperthyroidism were at greater risk of all-cause mortality.

When excluding the lowest quintile of TSH from the analysis, increasing levels of TSH correlated with an increasing risk of death. However, when the highest quintile of TSH was removed from the analysis, no clear interaction was observed. Kaplan-Meier confirmed that hyper- and hypothyroid CHF patients had impaired survival than their euthyroid comparators.

However, multivariable adjustments for confounders attenuated the effect of all three thyroid dysfunction measures (hyperthyroidism, hypothyroidism, and increasing TSH concentrations) on survival.

Instead, age, a higher New York Heart Association class, and increasing levels of the N-terminal pro-B-type natriuretic peptide were found to be the strongest independent predictors of mortality. The same three factors were significantly predictive of the secondary outcome, while thyroid dysfunction was not.