Overt hypothyroidism and low levels of free triiodothyronine (fT3) are both independent predictors of all-cause mortality in people hospitalized with acute heart failure, according to research published in Internal and Emergency Medicine.

Current literature on low thyroid function does not comparatively assess the effect of overt hypothyroidism, subclinical hypothyroidism, and low fT3 levels on in-hospital mortality among people hospitalized with acute heart failure. To mitigate this, researchers conducted a retrospective study to examine the prognostic role of these conditions in terms of all-cause mortality in this patient population.

A total of 6930 patients between 2016 and 2018 presented to the emergency department with suspected acute heart failure. After applying exclusion criteria, 6105 patients were admitted and included in the study, 17% of whom underwent an evaluation of their thyroid hormone levels within 72 hours of initial presentation (n=1018; average age, 81 years; 80% NYHA class III-IV).


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Among these patients, 798 had normal thyroid function, 105 had subclinical hypothyroidism, and 115 had overt hypothyroidism. The most common cardiovascular comorbidities included arterial hypertension, coronary artery disease, and atrial fibrillation.

All-cause, in-hospital mortality was higher among people with overt hypothyroidism compared with the subclinical hypothyroidism and normal thyroid function groups (27%, 17%, and 11%, respectively). Thirty-day survival was lower for patients with hypothyroidism but was statistically significant only in the overt hypothyroidism group.

Results of a univariate analysis found that older age, more severe NYHA class, higher levels of N-terminal prohormone brain natriuretic peptide (NT-proBNP), and diagnoses of COPD and dementia were all associated with in-hospital mortality. According to researchers, an fT3 cut-off level of less than 1.8 pg/mL was the best predictor of a worse outcome (sensitivity, 68.3; specificity, 77.4).

For NT-proBNP, a cut-off value of 5250 pg/mL was identified. A ROC analysis found that age greater than 80 years was the best predictor of intra-hospital death.

Finally, results of a multivariate Cox regression analysis found that overt hypothyroidism (hazard ratio [HR], 2.13; 95% CI, 1.41-3.22) and fT3 level less than 1.8 ng/mL were independent predictors of in-hospital death (HR, 3.39; 95% CI, 2.27-5.07); no significant association was found with subclinical hypothyroidism. Other statistically significant variables included age greater than 80 years, NYHA class IV, and NT-proBNP above 5250 pg/mL (HRs, 1.79, 2.02, and 3.00, respectively).

Study limitations include the single center design, which limits generalizability, minor variability in timing of thyroid hormone evaluation, and a lack of standardization of acute heart failure treatment between patients.

“Our findings confirm the importance of testing thyroid function in these patients, as already recommended by the guidelines on diagnosis and management of [acute heart failure],” the researchers concluded. “In addition, future studies should be considered to evaluate the treatment of selected patients with [acute heart failure] who could benefit from a T3 replacement approach.”

Reference

De Matteis G, Covino M, Burzo ML, et al. Prognostic role of hypothyroidism and low free-triiodothyronine levels in patients hospitalized with acute heart failure. Intern Emerg Med. Published online January 2, 2021. doi:10.1007/s11739-020-02582