2-DIMENSIONAL LEFT-VENTRICULAR DEFORMATION DURING SYSTOLE USING MAGNETIC-RESONANCE-IMAGING WITH SPATIAL MODULATION OF MAGNETIZATION

Background Myocardial tissue tagging with the use of magnetic resonanc e imaging allows noninvasive regional analysis of heart wall motion an d deformation. However, any evaluation of the effect of disease or tre atment requires a baseline reference of normal values and variation. W e studied the two-dimensional motion of material points imaged within the left ventricular wall using spatial modulation of magnetization (S PAMM) in 12 normal human volunteers. Methods and Results Five parallel short-axis and five parallel long-axis slices were acquired at five t imes during systole. SPAMM tags were generated at end diastole using a 7-mm grid. Intersection point data were analyzed for displacement, ro tation, and torsion, and triangles of points were analyzed for local r otation and principal strains. Short-axis displacement was the least i n the septum for all longitudinal levels (P<.001). Torsion about the l ong axis was uniform circumferentially because of the motion of the ce ntroids used to reference the rotation. In the long-axis images, the b ase displaced longitudinally toward the apex, with the posterior wall moving farther than the anterior wall (13.4+/-2.2 versus 9.7+/-1.8 mm, P<.001) in this direction. The largest principal strain (maximum leng thening) was approximately radially oriented in both views. In the sho rt-axis images, the minimum principal strain (maximum shortening) incr eased in magnitude toward the apex (P<.001) with little circumferentia l variation, except at midventricle, where the anterior wall showed gr eater contraction than the posterior wall (-0.21+/-0.03 versus -0.19+/ -0.02, P<.02). Conclusions Consistent regional variations in deformati on are seen in the normal human heart, Displacement and maximum shorte ning strains are well characterized with two-dimensional magnetic reso nance tagging; however, higher-resolution images will be required to s tudy transmural variations.