ORIGINAL ARTICLE The significance of transient ischemic dilation in the setting of otherwise normal SPECT radionuclide myocardial perfusion images Carolina Valdiviezo, MD, a,b Apurva A. Motivala, MD, a,c Rory Hachamovitch, MD, MSc, d Murthy Chamarthy, MD, a,e Pablo C. Navarro, MD, a,f Robert J. Ostfeld, MD, MSc, a Mimi Kim, ScD, g and Mark I. Travin, MD a Background. Transient ischemic dilation (TID) in the setting of an abnormal SPECT radionuclide myocardial perfusion imaging (MPI) study is considered a marker of severe and extensive coronary artery disease (CAD). However, the clinical significance of TID and its association with CAD in patients with an otherwise normal MPI study is unclear. Methods. From a database of patients who underwent MPI over a 9-year period, 96 without known cardiac history who had normal image perfusion patterns, and who underwent coronary angiography within 6 months, were identified. TID quantitative values were derived. To adjust for varying stress and image protocols, a TID index based on published threshold values was derived for each patient, with >1 considered as TID. We examined the relationship of TID to the presence/extent of CAD, and to a CAD prognostic index. TID was also correlated with patient survival. To address referral bias, survival in a separate cohort of 3,691 patients with a normal perfusion MPI who did not undergo angiography in the 6-month interval was correlated with the presence and severity of TID. Results. For 28 (29.2%) patients with normal MPI perfusion patterns but with TID, there was no increased incidence of CAD, multivessel or left main disease, or a higher prognostic index compared with no TID. In addition, there was no increased mortality associated with TID in both the angiography cohort and in the patients who did not undergo immediate angiography. Conclusions. TID in patients with an otherwise normal SPECT MPI study does not increase the likelihood of CAD, its extent or severity, and is not associated with worsened patient survival. (J Nucl Cardiol 2011;18:220–9.) Key Words: Myocardial perfusion imaging Æ transient ischemic dilation Æ coronary artery disease INTRODUCTION Transient ischemic dilation (TID) of the left ven- tricle on a stress single-photon emission computed tomography (SPECT) radionuclide myocardial perfu- sion imaging (MPI) study is thought to reflect myocardial ischemia that is sufficiently severe and extensive to cause visually apparent LV enlargement on the post-stress relative to the post-rest images. Several pathophysiologic mechanisms have been proposed, including actual stress-induced transient cavity dila- tion, 1 a lack of subendocardial tracer uptake in the setting of extensive subendocardial ischemia without true anatomic cavity enlargement, 2 a stress induced decrease in LV systolic function from stunning that appears as TID in the summed SPECT images, 3,4 or perhaps various combinations of these. Regardless of the mechanism of the phenomenon, the presence of TID in patients with an abnormal MPI study has been shown to be a marker of severe and extensive CAD, 1,5-7 and in a few studies to confer increased risk for cardiovascular events. 8-10 From the Division of Cardiology/Department of Medicine, a Montefiore Medical Center, Bronx, NY; Johns Hopkins Medical Center, b Balti- more, MD; The New York Presbyterian Hospital, c New York, NY; Cleveland Clinic, d Cleveland, OH; Bridgeport Hospital, e Bridgeport, CT; Beth Israel Medical Center, f New York, NY; and Albert Einstein College of Medicine, g Bronx, NY. Presented in part at the American College of Cardiology 59th Annual Scientific Session, March 2010, Atlanta, GA. Received for publication Aug 17, 2010; final revision accepted Jan 19, 2011. Reprint requests: Mark I. Travin, MD, Division of Cardiology/ Department of Medicine, Montefiore Medical Center, Bronx, NY; mtravin@montefiore.org. 1071-3581/$34.00 Copyright Ó 2011 American Society of Nuclear Cardiology. doi:10.1007/s12350-011-9343-6 220