Endogenous Contrast T1rho Cardiac Magnetic Resonance for Myocardial Fibrosis in Hypertrophic Cardiomyopathy Patients

Background: Late gadolinium enhancement (LGE) is a standard method to evaluate myocardial fibrosis, but restricted due to contrast agent contraindications. Non-contrast T1rho can generate endogenous contrast, and detect fibrosis in chronic myocardial infarction. However, T1rho for hypertrophic cardiomyopathy (HCM) patients is still unreported. The present study aimed to investigate T1rho for fibrotic assessment and the clinical implication in HCM patients.

Methods: 18 HCM patients and 8 controls underwent T1rho, cine, and LGE cardiac magnetic resonance (CMR). T1rho relaxation time maps were created. Left ventricular (LV) parameters assessed included wall thickness, wall thickening, chamber volumes, ejection function, and fibrotic size. New York Heart Association (NYHA) functional classification was conducted.

Results: Hyper-T1rho value was identified in 12 HCM patients, consistent with LGE. The mean T1rho values of controls, LGE-negative patients, and remote myocardium of LGE-positive patients were 42.2±1.6ms, 43.9±2.5ms, and 42.5±1.2ms respectively, and these values showed no significant difference (all p>0.05). T1rho-3-SD and T1rho-4-SD fibrotic sizes (32.5±14.0% and 25.1±11.5%) did not differ from LGE fibrotic size (28.1±11.2%) (both p>0.05). For the fibrotic size, T1rho-3-SD method obtained the strongest correlation with LGE (r=0.88, p<0.001), and T1rho-4-SD obtained the minimal mean difference with LGE (-3.1%; -15.2 to 9.1%), compared with other SDs. All the fibrotic sizes assessed by both methods correlated directly with LV maximal end-diastolic thickness (all p<0.05). Negative correlation was found between T1rho-4-SD fibrotic size and LV ejection fraction (r=-0.49, p=0.11). T1rho-4-SD fibrotic size showed positive correlation with NYHA class (r=0.46, p=0.13).

Conclusions: T1rho CMR has potential to detect fibrosis in HCM patients. 4-SD may be the appropriate threshold for assessment.