Do we need a new definition for post-stress reduction in LVEF beyond the numerical values?

Is a reduction in LVEF post stress simply a percentage drop in EF that exceeds inter- and intraobserver variability of the technique used? Regardless of whether the resting EF is normal or abnormal, and more importantl point is if the post-stress EF remains within normal limits or becomes significantly abnormal? Indeed, gated SPECT variables are necessarily subject to error due to poor edge detection especially when we consider the different loading conditions in the post-stress and rest states. In such cases, outlying measurements lead to false values especially with otherwise normal MPI. Because post-stress reductions in LVEF and TID are inherently “high-risk” findings, it is essential to understand the probability of being falsely positive. However, before reaching to this conclusion, we need to make sure that we chose the true index of severity: TID versus mere post-stress reduction in LVEF. Mandour Ali et al. reported that simple post-stress LV cavity dilatation in otherwise normal MPI studies should be only cautiously reported as a high-risk finding of significant CAD, instead it is better considered as a measurement variance.5 This is particularly true for vasodilator stressors based on the reports that showed that vasodilator-stress by itself was associated with post-stress reduction in LVEF. So that in such situation TID should be only cautiously interpreted as a marker of high-risk CAD.16 Valdiviezo et al. reported that there was neither significant difference between survival nor in severity of CAD among those with normal SPECT scans in the presence of TID after 9 years of follow-up.17 Abidov et al. reported approximately 1% per year increase in event rate among patients with normal MPI in presence of TID, but only in the highest quartile of elevated TID values.18 Gomez et al. demonstrated that, a decrease in post-regadenoson LVEF showed low specificity for severe/extensive CAD and conferred no prognostic value even among those with > 10% reduction in post-stress LVEF.4 So, on basis of these multiple reports do we need to set a new definition of this phenomenon that could improve its predictive accuracy and eliminate the confounder factors? Authors of this editorial suggest that establishing a new definition of post-stress reduction in LVEF is probably the key word to rearrange the mixed data in this area and improve specificity of this finding in predicting high-risk CAD.