Objectives: This study attempted to determine the benefit of a 5-min dobutamine stress echocardiographic stage versus a 3-min stage in a canine model.
Background: Dobutamine stress echocardiography, as currently performed, uses a variety of different protocols. Among the many aspects of dobutamine stress echocardiographic protocols that vary is stage duration. Because dobutamine has specific pharmacodynamics, it is possible that stages of different durations may have different cardiovascular effects.
Methods: Paired dobutamine stress echocardiograms were obtained in 10 open chest instrumented dogs. The stage duration for the initial dobutamine stress echocardiogram was randomly allocated to either 3 or 5 min, and all hemodynamic and echocardiographic variables were allowed to return to baseline before the second dobutamine stress echocardiogram was obtained using the alternative stage duration. At each stage, heart rate, systolic blood pressure, coronary flow, myocardial wall thickness and left ventricular cavity area were recorded. Cavity obliteration, hypotension, ventricular tachycardia or a maximal dose of 40 micrograms/kg body weight per min served as the dobutamine stress echocardiographic end point.
Results: At baseline, no difference was detected between the 3- or 5-min protocols for heart rate, systolic blood pressure, rate-pressure product, coronary blood flow, wall thickness or percent area change. Heart rate, systolic blood pressure and coronary flow increased more by the 10-micrograms/kg per min dose with the 5-min protocol than with the 3-min protocol. The dobutamine stress echocardiographic end points were achieved at a lower dobutamine dose (15.0 +/- 4.1 vs. 11.0 +/- 2.1 micrograms/kg per min [mean +/- SD], p = 0.01) with the longer stage duration.
Conclusions: In this canine model, a longer stage produced a greater hemodynamic effect at a lower peak dose. Thus, extending stage duration in clinical dobutamine stress echocardiography may achieve equivalent physiologic stress at lower doses and contribute to the optimization of dobutamine stress echocardiographic protocols.