Association between increased mortality and mild thyroid dysfunction in cardiac patients

Background. The effects of subclinical thyroid dysfunction on cardiac outcome are not well-defined.We though to assess the relationship between mild thyroid dysfunction and the incidence of death in cardiac patients. Methods. A total of 3121 cardiac patients underwent thyroid evaluation. Cardiac and overall deaths were considered. Four groups were defined: euthyroidism, subclinical hypothyroidism, subclinical hyperthyroidism, and low-triiodothyronine syndrome. Results. After a 32-month mean follow-up, the number of cardiac and overall death was 65 and 140 (3.4 and 7.3%) in euthyroidism, 15 and 27 (7.2 and 13%) in subclinical hypothyroidism, 8 and 9 (8.2 and 9.2%) in subclinical hyperthyroidism, 59 and 119 (6.5 and 13.1 %) in low-triiodothyronine syndrome patients, respectively. Survival rate for cardiac death was lower in subclinical hypothyroidism, subclinical hyperthyroidism and low-triodothyronine syndrome than in euthyroid patients (log rank test = 19.46, p0.001). Survival rate for overall death was lower in patients with subclinical hypothyroidism and low-triiodothyronine syndrome than in euthyroid patients (log rank test