Three-dimensional left ventricular deformation in hypertrophic cardiomyopathy

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.