Abnormal left ventricular longitudinal functional reserve in patients with diabetes mellitus: implication for detecting subclinical myocardial dysfunction using exercise tissue Doppler echocardiography

Background: Sublinical myocardial dysfunction occurs in a significant number of patients with type 2 diabetes. Assessment of ventricular long- axis function by measuring mitral annular velocities using tissue Doppler echocardiography ( TDE) is thought to provide a more sensitive index of systolic and diastolic function. We hypothesised that augmentation of left ventricular ( LV) longitudinal contraction and relaxation during exercise would be blunted in patients with type 2 diabetes. Methods: Mitral annular systolic ( S') and early diastolic ( E') velocities were measured at rest and during supine bicycle exercise ( 25 W, 3 min increments) in 53 patients ( 27 male, mean age 53 +/- 14 years) with type 2 diabetes and 53 subjects with age and gender- matched control. None had echocardiographic evidence of resting or inducible myocardial ischaemia. Results: There were no significant differences in mitral inflow velocities at rest between the two groups. E' and S' at rest were also similar between the groups. However, S' (7.1 +/- 1.3 vs 8.3 +/- 1.8 cm/ s at 25 W, p = 0.0021; 8.1 +/- 1.5 vs 9.1 +/- 2.0 cm/ s at 50 W, p = 0.026) and E' (8.5 +/- 2.3 vs 9.9 +/- 3.1 cm/ s at 25 W, p = 0.054; 9.1 +/- 2.1 vs 10.9 +/- 2.5 cm/ s at 50 W, p = 0.0093) during exercise were significantly lower in patients with diabetes compared with controls. Longitudinal systolic and diastolic function reserve indices were significantly lower in patients with diabetes compared with that of controls ( systolic index, 0.6 +/- 0.70 vs 1.2 +/- 1.5 cm/ s at 25 W, p = 0.029; 1.2 +/- 1.2 vs 2.1 +/- 1.6 cm/ s at 50 W, p = 0.009; diastolic index, 1.9 +/- 1.2 vs 2.5 +/- 2.2 cm/ s at 25 W, p = 0.07; 2.3 +/- 1.3 vs 3.2 +/- 2.2 cm/ s at 50 W, p = 0.031). Conclusion: In conclusion, unlike resting mitral inflow and annular velocities, changes of systolic and diastolic velocities of the mitral annulus during exercise were significantly reduced in patients with type 2 diabetes compared with the control group. The assessment of LV longitudinal functional reserve with exercise using TDE appears to be helpful in identifying early myocardial dysfunction in patients with type 2 diabetes.