Contemporary relevance of TID: Based on the company it keeps

Excerpt

A fundamental strength of SPECT myocardial perfusion imaging (MPI) has been the low event rate in most patients with a negative scan, as low as 0.6%·year⁻¹ in those undergoing exercise stress.1 However, the rate is higher in other populations such as those undergoing vasodilator stress (1.8%·year⁻¹), in part due to the occurrence of balanced ischemia, in which patients with multivessel ischemia have normal relative perfusion patterns.2 Multiple ancillary variables assist in detecting high-risk patients with normal perfusion scans, including exercise workload, ischemic ST-changes, and functional abnormalities on gated-SPECT.3,4 One such marker, transient ischemic dilation (TID), is well documented to provide incremental diagnostic and prognostic value, although there is controversy regarding its appropriate application across varying clinical situations. …