Abstract 337: Non-invasive Quantification of Myocardial Fibrosis in Diabetic Mice by T2 Time Measurement Using in-vivo High-resolution MRI and Correlation With Arrhythmias
Background: There is an established role for MRI in the assessment of myocardial fibrosis, in ischaemic and non-ischaemic cardiomyopathies. T2 relaxation time directly depends on physico-chemical properties of each tissue. Thus, myocardial T2 time determination can help in quantifying fibrosis. Diabetic cardiomyopathy usually includes interstitial fibrosis.
Purpose: To describe a non-invasive method using high-resolution myocardial T2 time measurement to assess myocardial fibrosis in diabetic mice in vivo and to correlate this fibrosis with ventricular arrhythmias.
Methods: Cine-FLASH sequences for morphology and function were followed by two multi-slice spin-echo sequences for T2 time assessment, respectively at 20 and 9 ms echo time (resolution 85×85 μm2, slice thickness 1.0 mm, imaging time 15 minutes), in ten 16-week old C57Bl/6J after 8 weeks of streptozotocin-induced diabetes, and ten control mice, under isoflurane anesthesia using a 11.75T system. Programmed atrial and ventricular stimulation was then realized to assess arrhythmias inducibility in both groups. MRI measurements were compared with histological quantification of collagen deposits using picrosirius red staining.
Results: T2 time was significantly lower in diabetic mice (13.8±2.8 ms versus 18.9±2.3 ms in the control group; p < 0.05). This was associated with a significant increase incollagen deposits, as evaluated by picrosirius red staining, in diabetic mice. Morphologic and functional analysis showed no difference in terms of ejection fraction (60.70±5 % versus 60.35±4 %) between the two groups, but end-systolic(1.28±0.26 μL/g versus 1.04±0.24 μL/g) and end-diastolic volumes (3.22±0.60 μL/g versus 2.67±0.65μL/g) were significantly increased in the diabetic group. During the electrophysiological study, 3 non sustained ventricular tachycardias were induced in diabetic mice (none in the control group) and 4 supra-ventricular arrhythmias (none in the control group).
Conclusion: In diabetic cardiomyopathy, T2 assessment can detect the presence of fibrosis at an early stage, before the apparition of a more obvious systolic dysfunction. Myocardial fibrosis may be a potential substrate for the genesis of (supra)-ventricular arrhythmias in diabetes mellitus.