Influence of Microporous Structures on Mural Thrombosis and Endothelialization at Blood-Contacting Surfaces

The influence of microporous structures in the walls of small-diameter arterial prostheses was investigated with the aim of minimizing thrombosis and enhancing endothelialization of blood-contacting surfaces. Six types of spongy polyurethane-polydimethylsiloxane grafts (PUG), 1.5-mm in an internal diameter and 1.5-2 cm in length, were implanted end-to-end in the infrarenal aorta of 66 adult rats. Some had a continuous inner skin and a hydraulic permeability (HP) of Oml/min/cm2at the standard transmural pressure of 120mmHg (PUG-S-0). Some had a discontinuous inner skin with some isolated windows connecting penetrating micropores though the graft wall and a mean HP ranging from 11 (PUG-S-11) to 37 (PUG-S-37) or 58 (PUG-S-58) ml/ min/cm2. The rest had a microporous inner surface with penetrating micropores through the graft wall and a mean HP of 2.7 (PUG-2.7) or 39 (PUG-39) ml/min/cm2. PUG which had a HP of less than 2.7 ml/min/cm2showed poor patency. PUG with a HP of more than 11 ml/min/cm2had acceptable patency, but endothelialization was limited to their anastomoses. In contrast, the patent PUG-S-37 and PUG-S-58 were largely endothelialized and all but one of the patent PUG-39 implants were completely endothelialized. In conclusion, penetrating micropores through the graft wall appear to inhibit critical mural thrombosis. A microporous inner surface seems to be superior to a skinned inner surface in achieving a high degree of endothelialization.