Subclinical hypothyroidism is an independent predictor of adverse cardiovascular outcomes in patients with acute decompensated heart failure.
OBJECTIVE
Altered thyroid hormone metabolism characterized by a low triiodothyronine (T3), so-called low-T3 syndrome, is a common finding in patients with severe systemic diseases. Additionally, subclinical thyroid dysfunction, defined as abnormal thyroid stimulating hormone (TSH) and normal thyroxine (T4), causes left ventricular dysfunction. Our objective was to identify the prevalence and prognostic impact of low-T3 syndrome and subclinical thyroid dysfunction in patients with acute decompensated heart failure (ADHF).


RESULTS
We examined 274 ADHF patients who were not receiving thyroid medication or amiodarone on admission (70 ± 15 years, 156 male), who underwent thyroid function tests. Euthyroidism was defined as TSH of 0.45 to 4.49 mIU/L; subclinical hypothyroidism as TSH of 4.5 to 19.9 mIU/L; and subclinical hyperthyroidism as TSH < 0.45 mIU/L, with normal free T4 level for the last two. Additionally, low-T3 syndrome was defined as free T3 < 4.0 pmol/L among euthyroidism subjects. On admission, 188 patients (69%) showed euthyroidism, 58 (21%) subclinical hypothyroidism, 5 (2%) subclinical hyperthyroidism, and 95 (35%) low-T3 syndrome. Cox proportional hazards models revealed that higher TSH, but not free T3 and free T4, was independently associated with composite cardiovascular events, including cardiac death and re-hospitalization for heart failure. Indeed, subclinical hypothyroidism was an independent predictor (hazard ratio: 2.31; 95% confidence interval: 1.44 to 3.67;P< 0.001), whereas low-T3 syndrome and subclinical hyperthyroidism were not.


CONCLUSIONS
Subclinical hypothyroidism on admission was an independent predictor of adverse cardiovascular outcomes in ADHF patients, suggesting a possible interaction between thyroid dysfunction and the pathophysiology of ADHF.
Department of Cardiovascular MedicineNational Cerebral and Cardiovascular CenterSuitaJapan; Division of Cardiovascular Medicine, Department of Internal MedicineKobe University Graduate School of MedicineKobeJapan.
Tomohiro
T
Hayashi
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Takuya
T
Hasegawa
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Hideaki
H
Kanzaki
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Akira
A
Funada
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Makoto
M
Amaki
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Hiroyuki
H
Takahama
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Takahiro
T
Ohara
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Yasuo
Y
Sugano
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Satoshi
S
Yasuda
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Hisao
H
Ogawa
Department of Cardiovascular Medicine National Cerebral and Cardiovascular Center Suita Japan.
Toshihisa
T
Anzai
Acute decompensated heart failure; Subclinical thyroid dysfunction; Thyroid hormones