Mar 01, 1985 · The pericardial membranes were acellular. Histologically, all of the implanted e-PTFE membranes were acellular and covered by a thin fibrous Volume 89 Number 3 March. 1985 e-PTFE surgical membrane 4 5 3 Fig. 2. An e-PTFE surgical membrane (M) explanted 24 months after implantation. No epicardial reaction or adhesions were found.