Abstract 18780: Diminished Left Ventricular Myocardial Oxygen Demand During Dobutamine Stress Testing in the Elderly Reduces the Appearance of Inducible Wall Motion Abnormalities Indicative of Ischemia

Abstract

Background: It has been observed that dobutamine stress may be less sensitive in the elderly and in those with LVH. We hypothesized that, in the elderly, a reduced increment in myocardial oxygen demand with dobutamine produces false negative results. Methods: We prospectively performed dobutamine cardiovascular magnetic resonance (DCMR) on 276 consecutively recruited individuals aged 55-85 years with risk factors for CAD. Rate pressure product (RPP), assessment of LV wall motion and volumes, aortic pulse wave velocity (PWV a measure of aortic stiffness) and first pass gadolinium enhanced LV perfusion defects (PD) indicative of ischemia were obtained on a 1.5T scanner at rest and after dobutamine infused to achieve 80% of the maximum predicted heart rate. Myocardial oxygen demand was assessed by the systolic pressure volume area (PVA), measured as LV stroke work (SW), [mean arterial pressure * stroke volume] plus potential energy [(1/2*end-systolic pressure) * end-systolic volume]}. All measures were assessed independently by personnel blinded to other data or participant identifiers. Differences were assessed with t-test; p < 0.05 was significant. DCMR PD was considered as the gold standard for the detection of ischemia. Results: Participants averaged 68±8 years, were 80% white, 90% hypertensive, 43% diabetic and 55% men; all achieved target heart rate. With dobutamine, RPP increased 85% and LV end-diastolic volume index decreased. No subject had an inducible WMA without concomitant PD, but 28 had PD without inducible WMA (Table). In these false negatives, PVA was significantly lower (p= 0.03) and LVSW (p = 0.06) and PWV (p= 0.13) had strong trends toward being lower. The sensitivity of DCMR WMA for identifying PD indicative of ischemia was 33%. Conclusion: With dobutamine stress testing, the elderly had declines in LV preload and PVA. These findings provide a novel mechanistic explanation of why the elderly may have false negative wall motion during dobutamine stress.