ObjectiveTo evaluate the changes of left atrium structure and function in patients with subclinicalhypothyroidism（SCH）before and after treatment by real-time three-dimensional echocardiography（RT-3 DE）.MethodsThirty-one SCH patients（SCH group）who were received levothyroxine tablets in our hospital were selected.Another 33 cases of healthysubjects at the same period were selected as the control group.Follow-up echocardiography was performed in SCH group afterthyroid function returned to normal for 3 months. Left atrial conventional parameters were obtained by two-dimensionalultrasound

including left atrium diameter（LAD）

left ventricular ejection fraction（LVEF）

left atrium volume（LAV）

left atrialvolume index（LAVI）normalized by body surface area

early and late mitral diastolic blood flow velocity（peak E

peak A）

mitralvalve E peak deceleration time（EDT）

average value e’and E/e’. Left atrium structure parameters including left atriummaximum volume（LAVmax）

left atrium pre-systolic volume（LAVpre）

left atrium minimum volume（LAVmin）

left atrium totalemptying index（LAEF）

left atrium passive emptying index（LAp EF）and the left atrial active evacuation index（LAa EF）

the strain parameters including the left atrial reserve strain（LASr）

the left atrial duct strain（LAScd）and the left atrial contractionstrain（LASct）were obtained by RT-3 DE.The differences of the above parameters before and after treatment in SCH group andcontrol group were compared.Pearson correlation analysis was used to detect the correlation between TSH levels and LAEF

LAp EF

and LAa EF before treatment.ResultsThere were no statistical differences of LAD

LAV

LVEF

E peak

A peak

EDT

Late e’

Sep e’

e’

E/e’between the control group and the SCH group before and after treatment.Compared with the controlgroup and the SCH group before treatment

LAVpre A

LAVmin and LAa EF in the SCH group after treatment were decreased

while LAEF and LAp EF were increased

and the differences were statistically significant（all P<0.05）. LAVmax

LAVpre A

LAVmin

LAEF

LAp EF and LAa EF in the SCH group after treatment were not statistically significant compared with the controlgroup. There was no statistically significant difference of LAVmax among the groups. Compared with the SCH group beforetreatment

LASr and LAScd in the SCH group after treatment were increased

while LASct was decreased

and the differenceswere statistically significant（all P<0.05）.Compared with the control group

LASr and LAScd in the SCH group after treatmentwere decreased

while LASct was increased

the differences were statistically significant（all P<0.05）. Pearson correlationanalysis showed that TSH level was not correlated with LAEF before treatment（r=0.16

P=0.39）

negatively correlated withLAp EF（r=-0.44

P=0.01）

and positively correlated with LAa EF（r=0.45

P=0.01）.ConclusionThe left atrial volume andmechanical function damage of SCH patients can be detected early by RT-3 DE technology

and the left atrial damage of SCHpatients is significantly improved after treatment with levothyroxine tablets.