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Three-dimensional left ventricular deformation in hypertrophic cardiomyopathy
A A Young1, C M Kramer, V A Ferrari
1Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia.
Insights
Hypertrophic cardiomyopathy (HCM) patients exhibit reduced three-dimensional (3D) myocardial shortening. However, their left ventricular (LV) torsion, a measure of twisting motion, was significantly increased compared to healthy individuals.
Area of Science:
- Cardiology
- Biomedical Engineering
- Medical Imaging
Background:
- Hypertrophic cardiomyopathy (HCM) is characterized by normal or increased ejection fraction and reduced force-length relations.
- Three-dimensional (3D) motion and deformation of the left ventricle (LV) in vivo have not been fully assessed in HCM.
- Previous studies lacked detailed 3D analysis of cardiac mechanics in HCM patients.
Purpose of the Study:
- To reconstruct and assess 3D left ventricular (LV) motion and deformation during systole in patients with hypertrophic cardiomyopathy (HCM).
- To quantify regional differences in myocardial motion and strain in HCM.
- To compare 3D cardiac mechanics between HCM patients and normal volunteers.
Main Methods:
- Magnetic resonance tagging was used to reconstruct 3D LV motion during systole in 7 HCM patients and 12 healthy volunteers.
- Transmural tagging stripes were tracked using an active contour model to subpixel resolution.
- A 3D finite-element model interpolated displacement data and registered it on a regional basis for analysis.
Main Results:
- Longitudinal displacement of the LV base toward the apex was markedly reduced in HCM patients (7.5 mm vs 12.5 mm).
- Circumferential and longitudinal shortening were significantly reduced in the septum of HCM patients.
- Left ventricular (LV) torsion was significantly greater in HCM patients (19.9 degrees vs 14.6 degrees).
Conclusions:
- Patients with hypertrophic cardiomyopathy (HCM) demonstrate regionally reduced 3D myocardial shortening.
- Despite reduced shortening, left ventricular (LV) torsion is increased in HCM.
- These findings highlight altered 3D mechanics in HCM, with compensatory hyper-rotation.
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 ventricle (LV) during systole in 7 patients with hypertrophic cardiomyopathy (HCM) and 12 normal volunteers by use of magnetic resonance tagging.
Methods And Results:
Transmural tagging stripes were automatically tracked to subpixel resolution with an active contour model. A 3D finite-element model was used to interpolate displacement information between short- and long-axis slices and register data on a regional basis. Displacement and strain data were averaged into septal, posterior, lateral, and anterior regions at basal, midventricular, and apical levels. 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 +/- 2.5mm (SD) versus 12.5 +/- 2.0 mm, P < .001. Circumferential and longitudinal shortening were both reduced in the septum (P < .01 at all levels). The principal strain associated with 3D maximal contraction was slightly depressed in many regions, significantly in the basal septum (-0.18 +/- 0.05 versus -0.22 +/- 0.02, P < .05) and anterior (-0.20 +/- 0.05 versus -0.23 +/- 0.02, P < .05) walls. In contrast, LV torsion (twist of the apex about the long axis relative to the base) was greater in HCM patients (19.9 +/- 2.4 degrees versus 14.6 +/- 2.7 degrees, P < .01).
Conclusions:
HCM patients had reduced 3D myocardial shortening on a regional basis; however, LV torsion was increased.