Transient ischemic dilation: A powerful diagnostic and prognostic finding of stress myocardial perfusion imaging

TID is an abnormal finding in stress myocardial perfusion imaging that suggests severe and extensive CAD and signifies a worse prognosis. TID has been reported with exercise and pharmacologic stress testing, planar and SPECT imaging, and Tl-201, Tc-99m, and dual-isotope protocols. Underlying mechanisms include a combination of stress-induced subendocardial hypoperfusion, ischemic systolic dysfunction, and less likely physical LV dilation with severe ischemia. TID appears to represent a significant ischemic burden and, compared with increased pulmonary Tl-201 uptake, suggests less permanent LV dysfunction and more myocardium at risk. Stress-to-rest LV volume ratios of 1.12 (epicardial) and 1.22 (endocardial) have been consistently shown to be highly specific for severe and extensive CAD.[PUBLICATION ABSTRACT]