Cardiac magnetic resonance elastography: toward the diagnosis of abnormal myocardial relaxation

Abstract

Aim: To assess the potential of cardiac magnetic resonance elastography (MRE) for elasticity-based detection of abnormal left ventricular (LV) relaxation.

Materials and methods: Cardiac MRE was performed in 3 groups: young volunteers (n = 11; mean age, 31.7 years), older volunteers (n = 5; mean age, 54.8 years), and a group with relaxation abnormalities (n = 11; mean age, 58 years) identified by transthoracic echocardiography. Cine MR imaging served to measure LV volumes and global LV systolic function. Wave-amplitude-sensitive electrocardiograph-gated steady-state MRE was performed using an extended piston driver attached to the anterior chest wall. Phase contrast shear wave images were acquired in all 3 Cartesian components and combined to generate amplitude maps. This was done using the time-gradient operator for linear high-pass filtering and phase unwrapping followed by temporal Fourier transformation for extracting externally induced 24.13-Hz shear oscillations from intrinsic motion and blood flow. Amplitudes were evaluated in the left ventricle and normalized by wave amplitudes outside the heart, adjacent to the right ventricle.

Results: One patient and 1 young volunteer had to be excluded from final analysis because of considerable body movement during the acquisition of the MRE scans. Mean wave amplitudes in the remaining subjects were 0.22 ± 0.05 mm in young volunteers, 0.23 ± 0.09 in older volunteers, and 0.14 ± 0.03 mm in patients. The mean ratio of amplitudes inside the ventricle to the anterior chest wall was 0.62 ± 0.15 for young volunteers, 0.50 ± 0.09 for older volunteers, and 0.33 ± 0.08 for patients.

Conclusion: MRE identifies significantly reduced LV shear wave amplitudes in patients with mild relaxation abnormality. Thus, cardiac MRE provides a promising modality for an elasticity-based diagnosis of dysfunctional myocardial relaxation.