807-3 The Effect of Age on the Hemodynamic Response to Dobutamine

Although aging is associated with decreased beta-adrenergic responsiveness and many patients undergoing dobutamine stress echocardiography (DSE) are elderly, the effect of age on the hemodynamic response to dobutamine DOB) has not been reported. Furthermore, hypotension is frequently observed during DSE and the mechanism is controversial. Therefore, we examined the heart rate IHR) and systolic blood pressure (SBP) responses in2 gender-matched groups of subjects widely separated in age by 2 decades: an older group (age 73±4, n=42) and a younger group (age 53±7, n=41), during graded 3 minute infusions of DOB at 5, 10, and 20μg/kg/min, We excluded subjects who were on cardioactive medications or who had abnormal LV function or conduction defects.ResultsHR responses of the two groups were nearly identical at all doses. In contrast, SSP responses differed markedly (see figure). With increasing DOS dose, the young had an increase in SSP while the old had a progressive decrease in SBP (p<0.01 by ANOVA), even after adjusting for higher resting SBP in the old. The SSP response was not affected by wall motion or lV function.ConclusionAging markedly alters the blood pressure but not the heart rate response to DOB. These data may help explain the frequency of hypotension during DSE