Abnormal Left Ventricular Longitudinal Functional Reserve Assessed by Exercise Pulsed Wave Tissue Doppler Imaging in Patients with Subclinical Hypothyroidism

Abstract

Response of systolic and diastolic velocities of mitral annulus to exercise in patients with subclinical hypothyroidism (SCH) has not been explored previously. We sought to investigate whether SCH is associated with abnormal left ventricular (LV) longitudinal function reserve to exercise. Mitral annular systolic (S') and early diastolic (E') velocities were measured at rest and during supine bicycle exercise using tissue Doppler echocardiography (TDE) in 23 patients with newly diagnosed SCH and 25 controls. LV diastolic and systolic longitudinal function reserve indices were calculated. There were no significant differences in mitral inflow velocities at rest between groups except for LV end-diastolic dimension and LV end-systolic dimension, which were higher in the control group. E' and S' at rest were also similar between the groups. However, S' (9.8 +/- 1.5 vs. 11.3 +/- 1.5 cm/sec at 25 W, P = 0.001; and 11.3 +/- 1.8 vs. 13.1 +/- 1.8 cm/sec at 50 W, P = 0.001) and E' (13.8 +/- 1.4 vs. 15.7 +/- 1.6 cm/sec at 25 W, P < 0.001; and 15.6 +/- 1.6 vs. 18.2 +/- 1.5 cm/sec at 50 W, P < 0.001) during exercise were significantly lower in patients with SCH. Longitudinal systolic and diastolic function reserve indices were significantly lower in patients with SCH (systolic index, 1.4 +/- 0.9 vs. 2.5 +/- 0.9 cm/sec at 25 W, P = 0.001; and 2.7 +/- 1.3 vs. 4.1 +/- 1.2 cm/sec at 50 W, P = 0.001; diastolic index, 2.3 +/- 1.3 vs. 3.6 +/- 1.5 cm/sec at 25 W, P = 0.003; and 3.9 +/- 1.6 vs. 5.9 +/- 1.3 cm/sec at 50 W, P < 0.001). Assessment of LV longitudinal functional reserve with exercise using TDE appears to be helpful in identifying early myocardial dysfunction in SCH.