The 3 minutes increment of dobutamine dose protocol is most commonly used method in dobutamine stress echocardiography (DSE). But the precise hemodynamic response to dobutamine dosage and its difference by extending stage duration have not been well elucidated.

Nineteen healthy voluntary subjects with a mean age of 23.9±4.7 years were included. All subjects underwent 3-minutes incremental and 5-minnutes incremental protocol of DSE at random order in a same day. Heart rate, blood pressure, stroke volume, fractional shortening, rate-pressure product and cardiac output were measured every 3 minutes in 3-min protocol of DSE. In 5-min protocol, same variables were measured at 3 minutes of each stage as well as at 5 minutes.

1) Heart rate did not increase until 10 µg/kg/min dose and increased thereafter by increment of dobutamine dose 2) Fractional shortening and stroke volume increased markedly from the 5 µg/kg/min until 20 µg/kg/min dose and showed slow increase or plateau at a higher dobutamine dose. 3) Systolic blood pressure, cardiac output and rate-pressure product increased continuously from initial dose to maximal dose. 4) Although by extending stage duration to 5 minute in 5-min protocol produced greater hemodynamic effects than those measured at 3 minutes of each stage, there were no significant difference in the results of 3-min and 5-min protocol of DSE.

The increase of cardiac contractility most contributed to increase of cardiac output until 20µg/kg/min dose and the increase of herat rate contributed dominantly thereafter, thus the hemodynamic variables showed different responses to increment of dobutamine dose. There were no significant difference in hemodynamic effects between the two protocols. So it is considered that 3-min protocol of DSE gives similar hemodynamic information as 5-min protocol and is more time-saving method.