The follow‐up of progressive hypertrophic cardiomyopathy using magnetic resonance rotating frame relaxation times

Magnetic resonance rotating frame relaxation times are an alternative non‐contrast agent choice for the diagnosis of chronic myocardial infarct. Fibrosis typically occurs in progressive hypertrophic cardiomyopathy. Fibrosis has been imaged in myocardial infarcted tissue using rotating frame relaxation times, which provides the possibility to follow up progressive cardiomyopathy without contrast agents. Mild and severe left ventricular hypertrophy were induced in mice by transverse aortic constriction, and the longitudinal rotating frame relaxation times (T_1ρ) and relaxation along the fictitious field (T_RAFF2, T_RAFF3) were measured at 5, 10, 24, 62 and 89 days after transverse aortic constriction in vivo. Myocardial fibrosis was verified using Masson's trichrome staining. Increases in the relative relaxation time differences of T_1ρ, together with T_RAFF2 and T_RAFF3, between fibrotic and remote tissues over time were observed. Furthermore, T_RAFF2 and T_RAFF3 showed higher relaxation times overall in fibrotic tissue than T_1ρ. Relaxation time differences were highly correlated with an excess of histologically verified fibrosis. We found that T_RAFF2 and T_RAFF3 are more sensitive than T_1ρ to hypertrophic cardiomyopathy‐related tissue changes and can serve as non‐invasive diagnostic magnetic resonance imaging markers to follow up the mouse model of progressive hypertrophic cardiomyopathy.