Ultrasound strain Imaging of altered myocardial stiffness - Stunned versus infarcted reperfused myocardium

Background - In this study we evaluate the diastolic deformation of ischemic/reperfused myocardium and relate this deformation to tissue elastic properties. Methods and Results - Farm pigs were subjected to left anterior descending coronary artery occlusion followed by reperfusion to create either stunning ( n = 12) or transmural myocardial infarction ( n = 12). Ultrasound-derived radial strain rates (SR) and strain were measured in the ischemic and remote walls. Myocardial stiffness was estimated from diastolic pressure - wall thickness relationship obtained from preload alterations. At reperfusion, end-systolic strain (epsilon(sys)) was significantly reduced in both stunned and infarcted walls compared with their remote walls ( 3 +/- 3% versus 26 +/- 2% and 1 +/- 0% versus 33 +/- 5%, respectively; P < 0.0001) or baseline values. Diastolic passive deformation (epsilon(A)) and rates of deformation during early (E-SR) and late (A(SR)) diastole were comparable between stunned and remote walls (epsilon(A): 7.3 +/- 1.6% versus 7.9 +/- 1.9%; E-SR: - 2.7 +/- 0.4 s(-1) versus - 2.6 +/- 0.5 s(-1); A(SR): - 1.8 +/- 0.2 s(-1) versus - 1.9 +/- 0.3 s(-1); P = NS for all) but were of significantly lower magnitude in infarcted walls versus remote walls (epsilon(A): 1.1 +/- 0.2% versus 11.4 +/- 1.9%; E-SR: - 0.3 +/- 0.1 s(-1) versus - 2.4 +/- 0.4 s(-1); A(SR): - 0.3 +/- 0.1 s(-1) versus - 2.5 +/- 0.4 s(-1); P < 0.0001 for all). Stiffness coefficient of exponential diastolic pressure - wall thickness relation was higher for infarcted ( P < 0.05) but not for stunned walls ( P = NS) compared with their remote walls. Conclusions - Early after postischemic reperfusion and in the presence of severely reduced systolic deformation, diastolic passive deformation ( and rates of deformation) can distinguish stiff, noncompliant, transmurally infarcted myocardial walls from those more compliant walls containing viable but stunned myocardium.