807-4 Normal Hemodynamic Responses to Dobutamine Infusion in the Elderly

Abstract

Elderly patients undergoing conventional exercise stress testing (CST) rely predominantly on an increased preload (Starling mechanism) to augment cardiac output (CO). In contrast, younger patients rely predominantly on an increased heart rate (HR) and decreased systemic vascular resistance (SVR) to augment CO. To determine normal physiologic hemodynamic responses to incremental dobutamine Infusion in young (<65 yo) as compared to elderly (≥65 yo) patients, we analyzed the results of 50 consecutive patients with normal regional wall motion and normal ejection fraction at rest. All patients underwent 2-D echocardiography and continuous wave Doppler evaluation of the left ventricular outflow tract (LVOT) during each stage of the dobutamine infusion protocol. No patients developed regional wall motion abnormalities during dobutamine infusion. HR, velocity time integral (VTI) across the lVOT and end diastolic dimensions (EDD) were recorded. Stroke volume (SV = VTI × cross sectional area of LVOTL, CO (HR × SV) and SVR (80 × mean arterial pressure ÷ CO) were calculated. The mean % change from baseline of HR, Sv. EDD, SVR and CO are shown: 1) There is no statistical difference in the hemodynamic response to dobutamine in young versus elderly patients. 2) Elderly patients undergoing dobutamine stress testing augment their CO by increasing HR and SV, decreasing SVR and with no change in EDD. 3) This is in contrast to that observed during CST. 4) Adequate heart rate response in the elderly might be more important during dobutamine infusion than during CST.