Background: The Tei index reflects both systolic and diastolic ventricular function. The aim of this study was to assess the Tei index by tissue Doppler imaging (TDI) and also to evaluate the correlation with growth hormone (GH) and the Tei index and left ventricular (LV) function assessed by TDI in patients with acromegaly. Methods: We prospectively evaluated 25 patients with acromegaly and 27 control subjects. LV systolic and diastolic function was assessed by conventional echocardiography and TDI. Results: Peak E velocity and E/A ratio were lower in those with acromegaly than in those without (P = 0.01; P = 0.002, respectively). Deceleration time of the mitral E-wave (P = 0.01) and isovolumic relaxation time (IVRT) (P = 0.01) were higher in acromegalic patients than those in controls (P = 0.006, P = 0.002). Em (P = 0.01) and Em/Am (P = 0.001) were lower in patients with acromegaly than in controls. In patients with acromegaly, the Tei index was significantly higher than that in controls (0.49 +/- 13.4 vs 0.39 +/- 5.2, P = 0.005). GH was positively correlated with the Tei index (r = 0.65, P = 0.041), Em/Am (r = 0.63, P = 0.021), and interventricular septum (IVS) thickness (r = 0.65, P = 0.008) only in patients with acromegaly. LV diastolic dysfunction was detected 36% by conventional echocardiography and 48% by the Tei index derived from TDI in acromegalic patients. Conclusion: TDI analysis of mitral annular velocities is useful to assess LV diastolic dysfunction in patients with acromegaly. GH was positively correlated with the Tei index and LV diastolic dysfunction. The Tei index may be superior to conventional mitral Doppler indices for identification of LV diastolic dysfunction in patients with acromegaly.