NORMAL STROKE VOLUME AND CARDIAC-OUTPUT RESPONSE DURING DOBUTAMINE STRESS ECHOCARDIOGRAPHY IN SUBJECTS WITHOUT LEFT-VENTRICULAR WALL-MOTIONABNORMALITIES

Dobutamine stress echocardiography has become widely utilized for eval uation of coronary artery disease, but the expected responses of strok e volume and cardiac output to the high doses of dobutamine administer ed in these studies are not known. To determine these responses, strok e volume and cardiac output were measured with 2-dimensional Doppler e chocardiography at each stage of dobutamine stress echocardiography an d after administration of atropine in 47 patients without resting or i nducible wall motion abnormalities. Heart rate increased significantly at each stage of dobutamine infusion and after atropine. Mean blood p ressure decreased at the 5 mu g/kg/min dose, then showed little change . Stroke volume increased 27 +/- 18% from baseline, with significant i ncreases occurring at both the 5 and 10 mu g/kg/min doses (p < 0.00001 ). With higher doses of dobutamine, stroke volume tended to plateau or decrease. Mean changes in stroke volume were not significant between the doses of 10, 20, and 30 mu g/kg/min. The mean change in stroke vol ume from the 30 to the 40 mu g/kg/min dose was a significant decrease of 6.3% (p = 0.004); the decrease from the 40 mu g/kg/min dose to atro pine approached statistical significance (p = 0.06). Cardiac output in creased throughout dobutamine infusion. Stroke volume during dobutamin e stress echocardiography is commonly maximum at a dose of 20 mu g/kg/ min and tends to decline at higher infusion rates. At higher doses, in creases in cardiac output are mediated primarily by increases in heart rate.