Histology of the right ventricular outflow tract seen with picrosirius red collagen stain. (a, arrows) Collagen fibres are seen between myocytes and at the epicardial area on day 1 after PE, (b, arrow) in the damaged region at day 4 after PE, (c, arrow) in the endocardial side of the debrided, thinned outflow tract week 1 after PE and (d) in the endocardial side 6 weeks after PE. Sections are serial to those in Figures 5 and 7. Endocardial side is downward.