Noninvasive Measurement of Three- Dimensional Myocardial Deformation with Tagged Magnetic Resonance Imaging During Graded Local Ischemia

The purpose of this study was to investigate the relationship between three-dimensional (30) deformation patterns in the canine lefr ventricle and localized graded reductions in perfusion. Magnetic resanance (MR) tissue tagging in a clinical scanner was used to determine systolic 30 deformation throughout the left ventricle with 32-msec time resolution. Six dogs were studied at normal and reduced left anterior descending coronary arteryjow levels, for a total of 14 studies. Deformation was calculated by jtting a 30 displacement field to tag displacement data from three orthogonal sets of tags and taking spatial derivatives. A novel index of 30 radial mechanical function, calculated from the 30 strain tensor cornponents and the tissue incompressibility constraint, had a higher correlation (R = 0.94) with perfusion (colored microspheres) than any of the 30 kgrangian j5nite strain tensor components or wall thickening, As a function of the fraction of baseline perfusion, it was well jt by a linear relationship for subnormal perfusion with a slope of 0.46 I+- 0.05 and an intercept of -0.156 -t 0.026. Longitudinal strain was lost first with decreasing perfusion (48%), followed by circumferential (40%) andjnally radial function (35%). The strain method detected perfusion drops as small as 20%, and early paradoxical strain transients lasting 100 msec were seen only with ischemia. 30 strain changes can be noninvasively measured throughout the left ventricle with MR tissue tagging. MR imaging-derived strain indices, unique to 30 analysis, correlate most sensitively with regional perji4sion in the canine left ventricle.