Cardiac fibrosis. Collagen volume analysis of the left ventricle from Sham, MI and MI rats treated with açaí extract (100 mg/kg) during 4 weeks. (A) Picrosirius red staining of left ventricle under light microscopy (magnification 20×), showing collagen fibers in red color. (B) Collagen volume fraction of left ventricle (%). Values are mean ± S.E.M. *P < 0.05 vs. Sham. # P < 0.05 vs. MI.