Normal changes in left ventricular filling and hemodynamics during dobutamine stress echocardiography.

During high-dose dobutamine infusion, there is a dose-dependent increase in cardiac output, a reduction in systemic vascular resistance, a reduction in left ventricular size, an increase in the mitral A wave velocity, a reduction in the E/A velocity ratio, and a reduction in the isovolumic relaxation time, with little change in the rate-corrected isovolumic relaxation time. Left ventricular cavity obliteration is common. This information may be useful in defining the mechanism of hypotension commonly seen during dobutamine stress echocardiography. It is speculated that the diastolic behavior of the left ventricle during dobutamine stress echocardiography, especially the isovolumic relaxation time, may provide an additional indicator of early myocardial ischemia, but this needs to be confirmed by larger independent studies.