EFFECT OF INCREMENTAL DOBUTAMINE INFUSION ON CARDIAC VOLUMETRIC AND PERFORMANCE RESPONSES IN HEALTHY VOLUNTEERS

Abstract

Results: Nine of ten subjects experienced their maximal cardiac index (CI) response at the maximum dose of dobutamine. At this point, the mean cardiac index more than doubled over baseline (3.92 ± 0.35 to 7.81 ± 0.50 L/min/m2, p<.0001). A mean increase in heart rate of 67.8 ± 6.4 at baseline to 72.7 ± 4.9 (p<.0001) accounted for as much as 75.3% of the increase in CI. The remaining increase in CI was associated with the percent increase of stroke volume index of 22.6 ± 6.6% (p=.0081) from the baseline of 54.4 ± 3.7 mL/m2. Mean right and left ejection fractions were both increased signiicantly by approximately 15% (relative change) over baseline. Biventricular end-systolic volume indices either reached or strongly trended towards signiicant reductions but increases in end-diastolic volume indices did not. Conclusions: The cardiac response of normal volunteers to graded dobutamine infusion is characterized by a marked increase in cardiac index that is due primarily to an increase in heart rate. Increased ejection fraction with reduced end-systolic volumes contributed to at least half the increase in stroke volume with the remaining increase caused by dobutamine-associated augmentation of end-diastolic volumes. Dobutamine increases indices of cardiac contractility. How the response to dobutamine in disease states may differ will require additional studies.