AimTo study the effect of simvastatin on cardiac fibrosis of rats with diastolic heart failure (DHF).Methods30 SD rats were randomly divided into three groups: control group, DHF group and simvastatin group.DHF model was produced by abdominal aortic coarctation in the rats.The rats in simvastatin group were given simvastatin 2 mg/(kg·d) by intragastric administration for 4 weeks, the others were treated with equal isotonic Na chloride.After 4 weeks, cardiac function and hemorheology were assessed by echocardiography and catheterization.HE and Masson stainings were applied to observe altered myocardial histopathology and myocardial fibrosis, respectively.ResultsIn DHF group, IVS, LVPWT, LVMI, E/A ratio, SBP, DBP, LVSP, LVEDP, fiber tissue， ventricular perivascular collagen area (CA), inflammatory cell invasion and collagen volume fraction (CVF) were increased.Tau was prolonged and LV-dp/dtmax was decreased.While in simvastatin group E/A ratio, IVS, LVPWT, LVMI, SBP, DBP, LVSP, LVEDP, inflammatory cell invasion, fiber tissue, CA and CVF were significantly decreased, prolonged Tau was shortened, and LV-dp/dtmax was increased compared with DHF group.ConclusionSimvastatin improves cardiac diastolic function in rats with DHF by ameliorating myocardial fibrosis.