BIOCOMPATIBILITY OF POLYMER-COATED OVERSIZED METALLIC STENTS IMPLANTED IN NORMAL PORCINE CORONARY-ARTERIES

Polymer coatings have been suggested to decrease the thrombogenicity o f metallic intravascular stents. The purpose of the present study was to investigate the intimal response to two different polymers when use d 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 p olyether, dephenylmethane-4,4'-diisocyanate and butane diol as chain e xtender. In order to induce vascular wall injury, the stents were depl oyed using an oversized balloon. At 6 weeks follow-up, the angiographi c luminal diameter measured in four polyurethane-coated stents and in six bare metallic stents was similar and 20% less than immediately pos t-stenting. However, in four polyphosphazene-coated stents the differe nce was 65% (P = 0.01 when compared to bare metal). At post-mortem mor phometry the degree of luminal area stenosis was also similar in polyu rethane-coated and in bare metallic stents (32 +/- 7.6% vs. 39 +/- 14% , NS) but reached 81 +/- 19% in polyphosphazene-coated stents (P < 0.0 3 when compared to bare metal). Thus, poly(organo)phosphazene induced a more pronounced histiolymphocytic and fibromuscular reaction than am phiphilic polyurethane, which appeared to be promising as biocompatibl e stent coating and, consequently, as a potential carrier for vasoacti ve drugs.