Background: Systolic strain rate (SR) has been shown to correlate with the transmural extent of myocardial infarction (MI). Ischemic postconditioning (PC) decreases MI size. We aimed to determine whether SR may predict the reduction of left ventricular (LV) remodeling induced by PC in a murine model of ischemia-reperfusion.
Methods and results: C57BL6 mice underwent 60 minutes of left coronary artery occlusion followed by reperfusion. PC consisted of 3 cycles of 1 minute of reperfusion and 1 minute of ischemia performed immediately after reperfusion. After 24 hours of reperfusion, a first subset of mice was euthanized for determination of infarct size. An additional subset of mice underwent 3 months of reperfusion. Echocardiography and SR were serially assessed at baseline, 3 days, and 1, 2, 3 months after reperfusion. PC decreased the infarct size and increased SR values within infarcted segments as soon as 24 hours after reperfusion as compared with controls (14 ± 1 versus 6 ± 1 s(-1), P<0.001). Systolic SR was correlated with MI size assessed by the area of infarction/area at risk (r=-0.88, P<0.001). At 3 months, PC improved LV ejection fraction (55 ± 4 versus 45 ± 3%; P<0.05) and decreased LV dimensions as compared with controls. Strain rate at day 3 correlated with LV ejection fraction (0.75; P<0.001), end-systolic (r=-0.75; P=0.001), and end-diastolic volumes (r=-0.70; P<0.001) at month 3.
Conclusions: In this murine model of MI, SR accurately assessed the reduction in MI size induced by PC early after reperfusion and the subsequent reduction of LV remodeling.