3-DIMENSIONAL LEFT-VENTRICULAR DEFORMATION IN HYPERTROPHIC CARDIOMYOPATHY

Background In hypertrophic cardiomyopathy, ejection fraction is normal or increased, and force-length relations are reduced. However, three- dimensional (3D) motion and deformation in vivo have not been assessed in this condition. We have reconstructed the 3D motion of the left ve ntricle (LV) during systole in 7 patients with hypertrophic cardiomyop athy (HCM) and 12 normal volunteers by use of magnetic resonance taggi ng. Methods and Results Transmural tagging stripes were automatically tracked to subpixel resolution with an active contour model. A 3D fini te-element model was used to interpolate displacement information betw een short- and long-axis slices and register data on a regional basis. Displacement and strain data were averaged into septal, posterior, la teral, and anterior regions at basal, midventricular, and apical level s. Radial motion (toward the central long axis) decreased slightly in patients with HCM, whereas longitudinal displacement (parallel to the long axis) of the base toward the apex was markedly reduced: 7.5 +/- 2 .5 mm (SD) versus 12.5 +/- 2.0 mm, P<.001. Circumferential and longitu dinal shortening were both reduced in the septum (P<.01 at all levels) . The principal strain associated with 3D maximal contraction was slig htly depressed in many regions, significantly in the basal septum (-0. 18 +/- 0.05 versus -0.22 +/- 0.02, P<.05) walls. In contrast, LV torsi on (twist of the apex about the long axis relative to the base) was gr eater in HCM patients (19.9 +/- 2.4 degrees versus 14.6 +/- 2.7 degree s, P<.01). Conclusions HCM patients had reduced 3D myocardial shorteni ng on a regional basis; however, LV torsion was increased.