Predicting Myocardial Functional Recovery After Acute Myocardial Infarction: Relationship Between Myocardial Strain and Coronary Flow Reserve

Background and Objectives: The purpose of this study was to evaluate the relationship between myocardial strain and coronary flow reserve (CFR) in the prediction of myocardial functional recovery after acute myocardial infarction (AMI). Subjects and Methods: Consecutive patients with anterior ST elevation AMI were analyzed. Left ventricular (LV) strain, determined by 2-dimensional speckle tracking imaging and CFR, determined by intracoronary flow measurement, were obtained on the same day, 3-5 days after primary percutaneous coronary intervention. A-strain was defined as the mean systolic longitudinal strain of 11 LV segments (out of 18) assumed to be supplied by the left anterior descending coronary artery (LAD). Functional recovery was defined as improved wall motion >1 grade seen in at least 2 contiguous dysfunctional segments by echocardiography at the 6-month follow-up. Results: Of 20 patients, 8 patients had preserved CFR (>2.0) and 12 patients had impaired CFR (${\leq}$2.0). There were no differences between the 2 CFR groups in LV ejection fractions and wall motion score indices in the LAD territory. However, A-strain was greater in patients with preserved CFR than in patients with impaired CFR (-6.4${\pm}$2.0% vs. -4.6${\pm}$1.4%, p=0.03). A-strain and CFR correlated well with each other (r=-0.49, p=0.03). Ten of 20 patients showed functional recovery at 6 months. Of clinical and echocardiographic parameters, A-strain was the only predictor of recovery (odds ratio 2.02, 95% confidence interval=1.03-3.97, p=0.04). For predicting recovery, the sensitivity and specificity were 80.0% and 80.0%, respectively, for CFR (cutoff=1.60), and 60.0% and 90.0%, respectively, for A-strain (cutoff=-6.13%). Conclusion: Myocardial strain correlates well with the extent of microvascular integrity and can be used as a noninvasive method for predicting recovery after AMI.