- A bioabsorbable (polyglactin), nonrestrictive, external sheath inhibits porcine saphenous vein graft thickening. Jeremy, J.Y., Bulbulia, R., Johnson, J.L., Gadsdon, P., Vijayan, V., Shukla, N., Smith, F.C., Angelini, G.D. J. Thorac. Cardiovasc. Surg. (2004)