Although dobutamine stress combined with echocardiographic visualization of the heart has been used with success in patients with coronary artery disease, the technique relies on a qualitative assessment of the myocardial response. A quantitative assessment of the response to dobutamine may provide more accurate information. However, no data are available regarding the normal myocardial response to graded doses of dobutamine. To address this issue, we performed transesophageal echocardiography combined with dobutamine stress in 21 normal volunteers (15 men; age 56plus/minus7 years). The myocardial response was assessed as the systolic thickening of the myocardium at baseline and during the infusion of increasing doses of dobutamine. Analysis was performed utilizing the centerwall method which consists of measurements of the thickness of the myocardium in diastole and in systole. Dobutamine produced a dose-dependent increase in systolic thickening. This dose- response relationship was steep at low doses of dobutamine and became more gradual from 15 to 40 mcg/kg/min. In contrast, heart rate initially showed a slight rise and was then followed by sharp increases from 5-20 mcg/min with subsequent plateau from 25-40 mcg/min. No significant differences were observed during diffusion of dobutamine in the different myocardial regions. These data represent the quantitative myocardial response to dobutamine in normal humans and provide the basis for a quantitative analysis of the myocardial response to this form of stress in patients with coronary artery disease.
