Mohammadali Ghodsitrad - Assistant professor of nuclear medicine, Shahid Beheshti University of Medical Sciences

Background: Transient ischemic dilation (TID) on myocardial perfusion imaging (MPI) has been recognized as specific indicator for multi-vessel coronary artery disease, especially in the setting of concomitant perfusion defects. The clinical significance of TID in an otherwise normal MPI has been a subject of debate. Our study aims to define the coronary angiographic specificity of TID in the absence of significant perfusion defects as well as normal limits of TID in different stress tests.Methods: MEDLINE, PubMed, and Google scholar databases were inspected for studies between 2104-2018 where TID was compared with invasive or CT coronary angiography for evaluation of coronary arterystenosis or TID limits were defined. The results are narrated in a descriptive method.Results: 42 studies met the criteria of our search. The ratio above which TID was deemed present ranged from 1.13 to 1.38. Most studies demonstrated increased cardiac event rates in patients with TID and an abnormal MPI. In otherwise normal perfusion, TID in some studies showed to be an indicator of poor prognosis in patients with diabetes and/or a history of coronary disease but not in low risk patients.in some studies however TID did not show added incremental value.Conclusion: Although some studies suggest that presence of TID with an otherwise normal SPECT MPI study does not translate into a greater extent of coronary artery disease or increased risk for future major adverse cardiac events but TID on MPI without perfusion defects may warrant further ischemic workup.

TID, CAD, CT angiography, SPECT MPI, Coronary arteries angiography