Introduction: Studies suggesting the the peak mitral annular (MA) early diastolic velocity (e‘) can be used as a marker of longitudinal LV relaxation have utilised dobutamine to increase e‘, based on supposed lusitropic properties of this drug. As dobutamine also has inotropic effects, e’ is proportional to early diastolic MA excursion (EDMAE) and any increase in EDMAE must be due to enhanced systolic contraction, we investigated whether the dobutamine effect on e’ might be related to its inotropic effect. Methods: In 10 healthy male volunteers tissue Doppler imaging of the septum was performed during dobutamine infusion at 5 and 10mcg/kg/min for measurement of e‘, EDMAE (integral of the early diastolic signal) and systolic MA excursion (SMAE; integral of the systolic signal). Results: Compared to baseline there was an increase at the 5 mcg/kg/min dobutamine dose of both SMAE (2.12 to 2.37cm, P=0.04) and EDMAE (1.52 to 1.73cm, P=0.006) but there was no significant increase in e’ (15.6 to 16.4cm/s, P=0.37). The increase in EDMAE was sustained (1.72cm, 14.5% from baseline, P=0.006) at the 10 mcg/kg/min dose, whilst e’ increased (15.6 to 17.1cm/s, 9.5% from baseline, P=0.034) and SMAE returned to baseline values (2.12 to 2.15cm, P=0.83). EDMAE was correlated with e’ (r2=0.71, p=0.001) at baseline but no correlation was observed during dobutamine infusion at either dose. Conclusion: Dobutamine infusion increased LV long-axis contraction and any increase in e’ was accompanied by an increase in EDMAE. These findings suggest that dobutamine's effect on e’ is mostly due to its inotropic action.