SEGMENTAL MOTION AND DEFORMATION OF TRANSMURALLY INFARCTED MYOCARDIUM IN ACUTE POSTINFARCT PERIOD

Mechanical behavior of infarcted myocardium in the first week following coronary occlusion has not been well characterized. Prior unidimensional studies failed to account for perpendicular deformation or shearing. This study characterizes three-dimensional motion and deformation of transmural infarcts 1 wk after coronary ligation in seven sheep. Principal strains and systolic in-plane translation and rotation were calculated for triangular elements defined by tissue tagging in short- and long-axis magnetic resonance images. The magnitudes of the first and second principal strains were reduced in both the short- and long-ards planes 1 wk after infarction. In addition, the absolute angular difference between the direction of the first principal strain and the radial direction increased from 14.7 +/- 1.9 to 43.5 +/- 2.7 degrees in the short-axis plane and from 19.6 +/- 7.3 to 43.9 +/- 10.0 degrees (P < 0.05) in the long-axis plane. In-plane rigid-body translation and rotation were also reduced in both planes. In conclusion, marked reduction and reorientation of principal strains and reduction in segmental rigid-body motion characterize nonreperfused transmural myocardial infarctions 1 wk after coronary occlusion.