Abstract 15006: Speckle Tracking Based Quantitative Echocardiography in the Mouse Model of Closed Chest Ischemia-Reperfusion
Introduction: This study examined the reliability of non-invasive measurements of area-at-risk (AAR), infarct size (IS), and LV remodeling using speckle tracking based quantitative echocardiography in a clinically relevant closed-chest mouse model of ischemia-reperfusion (CCIR).
Methods: All mice were surgically instrumented 1 wk prior to CCIR by placing a loose suture-attached occluder over the LAD and externalizing sutures subcutaneously. To induce ischemia, suture ends were exposed and pulled tight for maximal ST elevation. Long-axis and serial short-axis echo cine-loops of the LV were obtained and analyzed by 3
Methods: 1) traditional visual based wall motion assessment (WMA), 2) speckle tracking (VevoStrain) analysis of segmental and global radial LV strain (SRI-S), and 3) VevoStrain analysis of a single long-axis image (SRI-L). Ex-vivo AAR and IS were assessed by histology.
Results: Two groups were examined. In an acute study, 13 mice with occluders placed at various LAD levels were made ischemic and imaged simultaneously before determining AAR by vital dyes. A close correlation existed between histologic and echo based AAR using all 3 methods, the strongest being SRI-S(r=0.9). In a chronic study, proximal LAD occlusion with AAR of 45±5% was used and ischemia duration was varied between 30, 60, and 90 min. Echoes were done during IR, and 1, 7, and 14 days post IR. Histologic IS was measured at 14 days. Echo data showed significant LV remodeling in the 90 min IR group (end-diastolic LV volume increased from 61±4 to 102±10 ul, p<0.01), while there was no significant remodeling in the 30 or 60 min groups. IS analysis showed a nearly equal strong correlation between both SRI-S and SRI-L (r=0.89 and 0.84) compared to histologic IS, again with SRI-S being stronger. In contrast, WMA showed a weak correlation with histologic IS (r=0.55), likely due to the non-transmural nature of infarcts in CCIR.
Conclusion: CCIR is a clinically relevant model of ischemic heart disease which eliminates the effects of an inflammatory response to thoracotomy and allows flexibility in choosing the duration and frequency of ischemia. Importantly, quantitative echo in its simplified version is an accurate and practical method to evaluate all aspects of post-IR remodeling.
- © 2013 by American Heart Association, Inc.