MR extracellular volume mapping and non-contrast T1ρ mapping allow early detection of myocardial fibrosis in diabetic monkeys

OBJECTIVE: To detect diffuse myocardial fibrosis in different severity levels of left ventricular diastolic dysfunction (DD) in spontaneous type 2 diabetes mellitus (T2DM) rhesus monkeys. METHODS: Eighteen spontaneous T2DM and nine healthy monkeys were studied. Echocardiography was performed for diastolic function classification. Cardiac magnetic resonance (CMR) imaging was performed to obtain extracellular volume fraction (ECV) maps and T1ρ maps at two different spin-locking frequencies. ECV values, T1ρ values, and myocardial fibrosis index (mFI) values which are based on the dispersion of T1ρ, were calculated. Global peak diastolic longitudinal strain rates (GSrL) were also obtained. RESULTS: Echocardiography results showed mild DD in nine T2DM monkeys and moderate DD in the other nine. The global ECV values were significantly different among healthy animals as compared with animals with mild DD or moderate DD, and the ECV values of animals with moderate DD were significantly higher as compared with those of mild DD. The mFI values increased progressively from healthy animals to those with mild DD and then to those with moderate DD. Diastolic function indicators (e.g., early diastolic mitral annulus velocity, GSrL) correlated well with ECV and mFI. CONCLUSIONS: Monkeys with T2DM exhibit increased ECV, T1ρ, and mFI values, which may be indicative of the expansion of extracellular volume and the deposition of excessive collagen. T1ρ mapping may have the potential to be used for diffuse myocardial fibrosis assessment. KEY POINTS: • Monkeys with T2DM exhibit increased ECV, T1ρ, and mFI values, which may be indicative of the expansion of extracellular volume and the deposition of excessive collagen. • The relationship between diastolic dysfunction and diffuse myocardial fibrosis may be demonstrated by imaging markers. • Non-contrast T1ρ mapping may have the potential to be used for diffuse myocardial assessment. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00330-018-5950-9) contains supplementary material, which is available to authorized users.