Sato Y, Yoshihisa A, Kimishima Y, Kiko T, Watanabe S, Kanno Y,
Abe S, Miyata M, Sato T, Suzuki S, Oikawa M, Kobayashi A,
Yamaki T, Kunii H, Nakazato K, Ishida T, Takeishi Y.

Can J Cardiol. 2018 Jan;34(1):80-87. doi: 10.1016/j.cjca.2017.10.021. Epub 2017
Nov 8.
Comment in:
Can J Cardiol. 2018 Jan;34(1):11-12.

BACKGROUND: It is widely recognized that overt hyper- as well as hypothyroidism
are potential causes of heart failure (HF). Additionally it has been recently
reported that subclinical hypothyroidism (sub-hypo) is associated with
atherosclerosis, development of HF, and cardiovascular death. We aimed to clarify
the effect of sub-hypo on prognosis of HF, and underlying hemodynamics and
exercise capacity.
METHODS: We measured the serum levels of thyroid stimulating hormone (TSH) and
free thyroxine (FT4) in 1100 consecutive HF patients. We divided these patients
into 5 groups on the basis of plasma levels of TSH and FT4, and focused on
euthyroidism (0.4 ≤ TSH ≤ 4 μIU/mL and 0.7 ≤ FT4 ≤ 1.9 ng/dL; n = 911; 82.8%) and
sub-hypo groups (TSH > 4 μIU/mL and 0.7 ≤ FT4 ≤ 1.9 ng/dL; n = 132; 12.0%). We
compared parameters of echocardiography, cardiopulmonary exercise testing, and
cardiac catheterization, and followed up for cardiac event rate and all-cause
mortality between the 2 groups.
RESULTS: Although left ventricular ejection fraction did not differ between the 2
groups, the sub-hypo group had lower peak breath-by-breath oxygen consumption and
higher mean pulmonary arterial pressure than the euthyroidism group (peak
breath-by-breath oxygen consumption, 14.0 vs 15.9 mL/min/kg; P = 0.012; mean
pulmonary arterial pressure, 26.8 vs 23.5 mm Hg, P = 0.020). In Kaplan-Meier
analysis (mean 1098 days), the cardiac event rate and all-cause mortality were
significantly higher in the sub-hypo group than those in the euthyroidism group
(log rank, P < 0.01, respectively). In Cox proportional hazard analysis, sub-hypo
was a predictor of cardiac event rate and all-cause mortality in HF patients (P <
0.05, respectively).
CONCLUSIONS: Sub-hypo might be associated with adverse prognosis, accompanied by
impaired exercise capacity and higher pulmonary arterial pressure, in HF
patients.