Polymer coatings have been suggested to decrease the thrombogenicity of metallic intravascular
stents. The purpose of the present study was to investigate the intimal response to two different
polymers when used as coatings for
stents implanted in normal porcine coronary arteries. Non-articulated
stainless steel-slotted tube
stents were coated with either a biodegradable poly(organo)phosphazene with
amino-acid ester side groups or a biostable
polyurethane prepared from an amphiphilic polyether, dephenylmethane-4,4'-diisocyanate and
butane diol as chain extender. In order to induce vascular wall injury, the
stents were deployed using an oversized balloon. At 6 weeks follow-up, the angiographic
luminal diameter measured in four
polyurethane-coated
stents and in six bare metallic
stents was similar and 20% less than immediately post-stenting. However, in four
polyphosphazene-coated
stents the difference was 65% (P = 0.01 when compared to bare
metal). At post-mortem morphometry the degree of
luminal area
stenosis was also similar in
polyurethane-coated and in bare metallic
stents (32 +/- 7.6% vs. 39 +/- 14%, NS) but reached 81 +/- 19% in
polyphosphazene-coated
stents (P < 0.03 when compared to bare
metal). Thus, poly(organo)phosphazene induced a more pronounced histiolymphocytic and fibromuscular reaction than amphiphilic
polyurethane, which appeared to be promising as biocompatible
stent coating and, consequently, as a potential carrier for vasoactive drugs.