Abstract 14344: The Magnitude and Time Course of Stress Induced Left Ventricular Transient Ischemic Dilation: A CMR Perspective

Abstract

Background: Transient ischemic dilation (TID) of the left ventricle is used in nuclear myocardial stress perfusion imaging to identify global myocardial ischemia due to multi-vessel atherosclerosis. Although the isotope is injected at peak stress, nuclear stress images are obtained 20-30 minutes later to allow for hepatic clearance of isotope. Cardiac MRI myocardial stress perfusion imaging is performed at peak regadenoson effect. Given the superior spatial resolution of CMR, it also useful for accurate assessment of LV dimensions, both at rest and after stress. This prospective study was designed to assess the time course of peak regadenoson TID with direct measurement of LV dimensions and volumes using CMR. Methods: A standard CMR myocardial perfusion protocol was modified by adding a short axis SSFP imaging sequence at the level of the papillary muscle tips, just before the 1st pass perfusion study at peak regadenoson effect, and again 20-30 minutes later, after delayed enhancement imaging was completed. Parameters for this study included LV end-diastolic diameter (EDD) and slice volume (EDV), LV end-systolic diameter (ESD) and slice volume (ESV). TID was defined as an increase in end-diastolic diameter at stress compared to rest. An independent sample t-test was used to compare mean values. Results: Data was obtained from 181 consecutive patients undergoing CMR stress studies over a 6 month period. Stress induced LV dilation occurred in 61 patients, but not in 120. Of 61 patients with stress induced LV dilation, the mean slice EDV at rest was 18.24 mL3 and increased to 19.83 mL3 at stress (p<.05). At 20-30 minutes post regadenoson, mean slice volume remained non-significantly elevated at 18.84mL3 (p=.415) relative to the baseline slice EDV. Of the 120 patients without stress induced dilation, mean slice EDV decreased from 21.10 mL3 at rest to 19.65 mL3 at stress (p<.05). Mean slice volume remained non-significantly decreased at 20-30 minutes post stress (p=.188). Conclusions: These data suggest that maximum TID occurs at the time of peak regadenoson effect and attenuates to baseline over 20-30 minutes. Because of the inherent delay in obtaining myocardial stress perfusion images with a nuclear technique, CMR stress assessment of TID may be preferable.