Rotating Frame Spin-Lock Cardiac MRI Method at 9.4 T Can Characterize Diffuse Fibrosis in Progressing Hypertensive...

This study aimed to investigate the applicability of rotating frame spin-lock continuous wave (CW) T_1ρ and relaxation along a fictitious field with Rank 2 (RAFF2) methods complementary to native T₁ and late gadolinium enhancement (LGE) for cardiac magnetic resonance imaging (CMRI) of diffuse fibrosis in mice with advancing hypertensive heart disease (HHD) and diastolic dysfunction.

HHD was induced in mice with angiotensin II infusion for 28 days; sham operated were used as controls. Phenotype progression was assessed with echocardiography. Characterization of diffuse fibrosis was performed with CMRI. CW-T_1ρ and RAFF2 were compared with native T₁ and LGE acquired on Days 14 and 28 of the experiment. Regions of interest in CMRI relaxation time maps and Picrosirius red-stained histological cardiac sections were compared.

Diffuse fibrosis in the left ventricle was visible on Day 14 with T_RAFF2 relaxation time maps in the HHD group with early diastolic impairment, and CW-T_1ρ showed a slight increase. Both CW-T_1ρ and T_RAFF2 showed elevated values on Day 28 in HHD mice, whereas native T₁ showed an increase only on Day 28. LGE showed no accumulation. The presence of diffuse fibrosis was verified with cardiac histology.

Rotating frame spin-lock CW-T_1ρ and RAFF2 are more sensitive to native T₁ and LGE in the characterization of diffuse fibrosis in advancing HHD in mice, being an alternative for the imaging of fibrotic remodeling also in other cardiac pathologies.