Healing and Long-Term Viability of Grafts in the Venae Cavae Reconstruction

Abstract

The need for superior vena cava (SVC) or inferior vena cava (IVC) recon struction is not uncommon: lung cancer, mediastinal tumors, or retroperitoneal neoplasms are the most frequent indications for caval replacement. Since auto genous veins, which represent the most satisfactory venous substitute, have not been applicable to caval replacement, because of the lack of suitable length and caliber, many types of materials have been tested in the venous system. The present study was planned to compare the potential of expanded polytetrafluoroethylene (e-PTFE) and glutaraldehyde-tanned human umbilical vein (HUV) grafts as caval substitutes. Patch (4 x 5 cm) reconstruction of the SVC was carried out in 10 dogs, tubu lar (3 x 10 mm) reconstruction of the SVC in 5 dogs, and patch (1 x 2 cm) recon struction of the IVC in 8 dogs. In the patch reconstruction groups, HUV grafts were used in half of the cases and 30 μm pore sizes e-PTFE grafts in the other half, while in the tubular SVC replacement group, only e-PTFE grafts were employed. The grafts were removed fifteen to thirty days after IVC patch re construction, thirty to two hundred seventy days after SVC patch reconstruc tion, and thirty-three to forty-one months after SVC tubular replacement. In every instance, specimens were obtained for light microscopy (LM) and scan ning electron microscopy (SEM). HUV patches implanted in the SVC showed hemorrhagic foci at their central portion and marked constriction at the anastomotic regions. On the contrary, the inner surface of e-PTFE patch grafts was covered with a uniform and glis tening neointima. By LM, e-PTFE patches showed a smooth and regular lumi nal surface, while the inner surface of HUV patches was irregular, with hemorrhagic areas in the underlying layers. By SEM, e-PTFE patches revealed a more rapid and orderly endothelialization of their inner surface than HUV patches did. Tubular SVC reconstruction showed the good long-term viability of the e-PTFE neointima (as long as forty-one months after grafting). Only spotty areas revealed neointima alterations, such as fibrinoid degeneration, fo cal necrosis, or minor thrombotic foci. In the IVC patch reconstruction model, HUV grafts showed an exuberant fibrin deposition on their inner surface and delayed endothelialization patterns, as compared with e-PTFE grafts. Since rapid healing with rapid endothelialization is accepted as the most important factor providing the graft luminal surface with the best antithrombotic proper ties, the present study demonstrated that e-PTFE is a more suitable material than HUV for SVC and IVC reconstruction.