[Meta-analysis on the association between subclinical hypothyroidism and the left ventricular functions under Doppler...

To explore the association between subclinical hypothyroidism and the left ventricular functions under conventional 2D Doppler echocardiography and to provide evidence for the protection of heart function.

Literatures regarding the association of subclinical hypothyroidism and the left ventricular functions were retrieved in large databases from home and abroad for the last 12 years. The left ventricular systolic function was assessed by left ventricular ejection fraction and the shortening of left ventricular fraction. The left ventricular diastolic function was assessed by left ventricular early diastolic filling flow velocity, late diastolic filling flow velocity, their ratios (E/A), and the left ventricular isovolumic relaxation time. The relationship between subclinical hypothyroidism and the left ventricular functions were assessed by Meta-analysis with Stata 11 software. The weighted mean difference (WMD) and 95% confidence interval (CI) were calculated, and the publication bias was assessed by Begg's test.

13 eligible papers were included. (1) Statistics on the combined data showed that in the evaluation of left ventricular diastolic function indicators. There were significant differences in left ventricular late diastolic filling flow velocity (WMD = 4.51, 95%CI: 2.41 to 6.61) and E/A (WMD = -0.22, 95%CI: -0.30 to -0.13), as well as the left ventricular isovolumic relaxation time (WMD = 6.13, 95%CI: 2.79 to 9.48) between patients with subclinical hypothyroidism and normal controls but, no significant difference was found in left ventricular early diastolic filling flow velocity. Looking at the left ventricular systolic function indicators. There were no significant differences in the left ventricular ejection fraction and left ventricular fractional shortening between patients with subclinical hypothyroidism and normal controls. (2) Data from the subgroup analysis showed that the differences of left ventricular late diastolic filling flow velocity, E/A and left ventricular isovolumic relaxation time were significantly different between patients with subclinical hypothyroidism and normal controls in the mean heart rate ≥ 72 bpm group. The difference of left ventricular isovolumic relaxation time was significantly different in the mean heart rate < 72 bpm group, and the difference of left ventricular late diastolic filling flow velocity was significant in the mean age < 60-year-old group.

Subclinical hypothyroidism was associated with the left ventricular diastolic dysfunction, but not associated with the left ventricular systolic dysfunction. The results suggested that subclinical hypothyroidism might change the heart function which could be evaluated by Doppler echocardiography.