Abstract 216: Change of Myocardial Strain With Mild Afterload Augmentation Can Reveal Concealed Functional Abnormalities in the Recently Ischemic Myocardium
Background: Wall motion abnormalities induced by myocardial ischemia disappear shortly after its relief. Therefore, to identify recently ischemic myocardium, ischemic “memory” imaging is desirable. Because afterload affects myocardial deformation, we hypothesized that afterload augmentation could reveal concealed functional abnormalities in the myocardium exposed to transient ischemia.
Methods: Left circumflex coronary artery was occluded for 4 minutes followed by 30-minute reperfusion in 10 dogs. After recovery of wall motion, afterload was mildly increased with phenylephrine infusion (PE, 1.0 μg/kg/min). Short-axis images were acquired at baseline, during occlusion, after reperfusion, and during PE using Vivid 7 (GE). The radial direction of peak systolic strain (ϵS), peak systolic strain rate (SRS), peak diastolic strain rate (SRD) and peak positive strain rate during isovolumic relaxation (as a parameter of postsystolic thickening, SRIVR) were measured in the risk and the opposite normal areas using speckle tracking echocardiography.
Results: Each parameter returned to the baseline level after reperfusion. Left ventricular systolic pressure increased from 113±9 to 146±22 mmHg. Before and during PE, ϵS and SRD did not change in the risk and normal areas. However, SRS decreased and SRIVR increased significantly only in the risk area (SRS 1.65±0.40 vs. 1.26±0.29/s, p < 0.05, SRIVR 0.14±0.23 vs. 0.32±0.31/s, p < 0.05). The receiver operating characteristics curve analysis demonstrated that the change of SRS (ΔSRS) after PE was most sensitive and specific for detecting ischemic memory (area under the curve 0.74).
Conclusion: The analysis of SRS with mild afterload augmentation can reveal concealed functional abnormalities in the recently ischemic myocardium and may be useful for ischemic memory imaging.