Fig. 1

Quantification of cardiac fibrosis in heart failure (HF) patients (n = 11) pre- and post-high-intensity interval trainings (HIIT). A. The region of interest (square) in short axis T1 mapping cardiovascular magnetic resonance with late-gadolinium enhanced (CMR-LGE) imaging of the left ventricle (LV) was used for myocardium extracellular volume (ECV) fraction studies to quantify the severity of LV fibrosis. B. The left panel shows the relaxation time (T1) of each region of interest (ROI) in a slice at middle cavity. The T1 was used to calculate the extracellular volume (ECV) fraction determined by the CMR-LGE system to estimate the myocardial fibrosis in the slice. The right panel shows the corresponding ROI. C. CMR-LGE imaging demonstrated ECV fractions at the basal, mid-cavity (Middle) and apical (Apex) myocardium segments pre- and post-HIIT. D. The mean ECV fractions of the total, Base, Middle, and Apex LV myocardium segments decreased significantly post-HIIT. Ant., Anterior; Post, Posterior; Sup., Superior; Inf., Inferior; RV, Right ventricle