Objective To explore the impact of small doses of thyroid hormone on the level of thyroid hormone and heart rate variability（HRV）in elderly patients with chronic heart failure（CHF）.Method 99 cases of CHF elderly patients received in a hospital of Daye city from March 2012 to December 2013 were divided into a control group（47cases）and an observation group（52cases）with random stratified method.The control group was given the conventional therapy for heart failure and the observation group was given small doses of thyroid hormone on the basis of the conventional therapy.The cardiac function

HRV-related indicators and the level of thyroid hormone of patients in both groups were compared before and after treatment.Results For all patients after the treatment

HRV time-domain indexes like 24-hour all sinus R-R standard deviation of NN intervals（SDNN）

all near the sinus R-R root-mean-square deviation of intervals（rMSSD）

every five-minute sinus R-R standard deviation of average NN intervals（SDANN）

heart rate of two adjacent sinus R-R deviation of intervals higher than 50 ms in the total percentage of heart rate（pNN50）and cardiac function parameters of left ventricular ejection fraction（LVEF）

E peak to A peak ratio（E/A）

6-minute walk distance（6-MWD）increased noticeably

left ventricular end-diastolic diameter（LVDd）narrowed

indicators of thyroid hormone like serum triiodothyronine（T3）

thyroxine（T4）

free triiodothyronine（FT3）and free thyroxine（FT4）tended to be on normal levels（P<0.05）;the improvement of cardiac function

all HRV time-domain indexes and levels of thyroid hormone in the observation group were significantly greater than those in the control group（P<0.05）.Conclusions The combination of small doses of thyroid hormone and conventional therapy for heart failure can significantly improve their HRV in elderly patients with CHF and get thyroid hormone back to normal levels to promote cardiac function

worthy of clinical promotion.