Abstract 4229: Subendocardial Ischemia May Explain ST-Segment Depression During Negative Stress Echocardiograms: A Study Of Endo-And Epicardial Strain With Velocity Vector Imaging
Purpose : ST depression (STD) is common during dobutamine stress echocardiography (DSE) and poorly predictive of coronary disease (CAD). We hypothesized that STD may be related to subendocardial ischaemia in individuals without inducible regional wall motion abnormalities (RWMA). We investigated this hypothesis using velocity vector imaging (VVI) to measure myocardial tissue deformation as an index of subendocardial ischemia.
Methods : Of a total study group of 50 patients without inducible RWMA (age 65 ± 12 years, 54% male), we studied 25 consecutive patients with a minimum of 1mm STD during DSE and compared them to 25 randomly selected controls without ST-depression. Mean Bethesda scores indicated a low 10-year risk of CAD (men 5.0±2.6%, women 6.1±3.0%). Longitudinal endocardial and epicardial peak strain (PS) and peak end-systolic strain (PESS) were measured (blinded) from 3 apical views using VVI. A total of 12 basal and mid-cavity segments at rest and peak stress were measured and averaged. 20 randomly selected patients were used to assess the inter-observer variability of the technique.
Results : There were no significant differences between groups in terms of baseline demographics, LV volumes, LV mass, EF, resting heart rate (HR) and peak systolic BP (SBP). The STD group had significantly higher resting SBP and lower peak HR. At rest, there were no significant differences in endocardial or epicardial PS or PESS. Intra-observer variability was low (mean ICC 0.55). At peak stress, the STD group had significantly lower endocardial PS (−16.8 ± 2.6% vs −14.6 ± 3.5%, p<0.05) and PESS (p<0.05, see table⇓) than the normal response group. There was no significant difference between groups in epicardial PS (p=NS) and PESS (p=NS, see table⇓).
Conclusion : ST-segment depression during DSE is associated with a significant reduction in endocardial but not epicardial strain when compared to those without ST segment change. This may reflect the influence of subendocardial ischemia.