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 (nϭ12) or transmural myocardial infarction (nϭ12). Ultrasound-derived radial strain rates (SR) and strain were measured in the ischemic and remote walls. Myocardial stiffness was estimated from
... as estimated from diastolic pressure-wall thickness relationship obtained from preload alterations. At reperfusion, end-systolic strain (⑀ sys ) was significantly reduced in both stunned and infarcted walls compared with their remote walls ( 3Ϯ3% versus 26Ϯ2% and 1Ϯ0% versus 33Ϯ5%, respectively; PϽ0.0001) or baseline values. Diastolic passive deformation (⑀ A ) and rates of deformation during early (E SR ) and late (A SR ) diastole were comparable between stunned and remote walls (⑀ A : 7.3Ϯ1.6% versus 7.9Ϯ1.9%; E SR : Ϫ2.7Ϯ0.4 s Ϫ1 versus Ϫ2.6Ϯ0.5 s Ϫ1 ; A SR : Ϫ1.8Ϯ0.2 s Ϫ1 versus Ϫ1.9Ϯ0.3 s Ϫ1 ; PϭNS for all) but were of significantly lower magnitude in infarcted walls versus remote walls (⑀ A : 1.1Ϯ0.2% versus 11.4Ϯ1.9%; E SR : Ϫ0.3Ϯ0.1 s Ϫ1 versus Ϫ2.4Ϯ0.4 s Ϫ1 ; A SR : Ϫ0.3Ϯ0.1 s Ϫ1 versus Ϫ2.5Ϯ0.4 s Ϫ1 ; PϽ0.0001 for all). Stiffness coefficient of exponential diastolic pressure-wall thickness relation was higher for infarcted (PϽ0.05) but not for stunned walls (PϭNS) 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.