Prevalence and functional significance of transient ST-segment depression during daily life activity: Comparisons of ambulatory ECG with stress redistribution thallium 201 single-photon emission computed tomographic imaging

Abstract To assess the prevalence and functional significance of ischemic ambulatory ECG responses, we prospectively performed ambulatory ECG monitoring in 244 patients (mean age 61 ± 10 years) referred for stress redistribution thallium 201 myocardial perfusion scintigraphy. The prevalence of ST-segment depression during ambulatory ECG was 33% among patients with a positive exercise ECG, but prevalence varied in selected patient subgroups. Among three groups with coronary artery disease (CAD), the group with ambulatory ECG ischemia (group 1) had a greater frequency of ischemic thallium responses ( p = 0.07), a greater median number of reversible thallium defects ( p p p = 0.002), occurred at a lower heart rate threshold ( p = 0.002), and lasted longer after exercise ( p = 0.001). Notably, one third of group 1 patients also manifested evidence of transient ischemic dilation of the left ventricle after exercise ( p