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.


METHODS
To assess the relationship between mild thyroid dysfunction and the incidence of death in cardiac patients, we evaluated 3121 cardiac patients. Cardiac and overall deaths were considered. Four groups were defined: euthyroidism, subclinical hypothyroidism (SCH), subclinical hyperthyroidism (SCT), and low triiodothyronine syndrome (low T3).


RESULTS
After mean follow-up of 32 months, there were 65 and 140 cardiac and overall deaths (3.4% and 7.3%), respectively, in euthyroidism, 15 and 27 (7.2% and 13.0%) in SCH, 8 and 9 (8.2% and 9.2%) in SCT, and 59 and 119 (6.5% and 13.1%) in low T3. Survival rates for cardiac death were lower in SCH, SCT, and low T3 than in euthyroidism (log-rank test; chi2 = 19.46; P < .001). Survival rates for overall death were lower in SCH and low T3 than in euthyroidism (log-rank test; chi2 = 26.67; P < .001). After adjustment for several risk factors, hazard ratios (HRs) for cardiac death were higher in SCH (HR, 2.40; 95% confidence interval [CI], 1.36-4.21; P = .02), SCT (HR, 2.32; 95% CI, 1.11-4.85; P = .02), and low T(3) (HR, 1.63; 95% CI, 1.14-2.33; P = .007) than in euthyroidism; HRs for overall death were higher in SCH (HR, 2.01; 95% CI, 1.33-3.04; P < .001) and low T3 (HR, 1.57; 95% CI, 1.22-2.01; P < .001) but not in SCT.


CONCLUSIONS
A mildly altered thyroid status is associated with an increased risk of mortality in patients with cardiac disease.
Iervasi
Giorgio
G
Clinical Physiology Institute, National Council of Research, Via Moruzzi 1, 56124 Pisa, Italy. iervasi@ifc.cnr.it
Molinaro
Sabrina
S
Landi
Patrizia
P
Taddei
Maria Chiara
MC
Galli
Elena
E
Mariani
Fabio
F
L'Abbate
Antonio
A
Pingitore
Alessandro
A
D003327:Coronary Disease / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006980:Hyperthyroidism / Q000150:complications*; D007037:Hypothyroidism / Q000150:complications*; D008297:Male; D008875:Middle Aged; D009026:Mortality; D016016:Proportional Hazards Models; D015996:Survival Rate; D014284:Triiodothyronine / Q000097:blood
D014284:Triiodothyronine