Stent thrombogenicity early in high-risk interventional settings is driven by stent design and deployment and protected by polymer-drug coatings.

BACKGROUND: Stent thrombosis is a lethal complication of endovascular intervention. Concern has been raised about the inherent risk associated with specific stent designs and drug-eluting coatings, yet clinical and animal support is equivocal. METHODS AND RESULTS: We examined whether drug-eluting coatings are inherently thrombogenic and if the response to these materials was determined to a greater degree by stent design and deployment with custom-built stents. Drug/polymer coatings uniformly reduce rather than increase thrombogenicity relative to matched bare metal counterparts (0.65-fold; P=0.011). Thick-strutted (162 µm) stents were 1.5-fold more thrombogenic than otherwise identical thin-strutted (81 µm) devices in ex vivo flow loops (P<0.001), commensurate with 1.6-fold greater thrombus coverage 3 days after implantation in porcine coronary arteries (P=0.004). When bare metal stents were deployed in malapposed or overlapping configurations, thrombogenicity increased compared with apposed, length-matched controls (1.58-fold, P=0.001; and 2.32-fold, P<0.001). The thrombogenicity of polymer-coated stents with thin struts was lowest in all configurations and remained insensitive to incomplete deployment. Computational modeling-based predictions of stent-induced flow derangements correlated with spatial distribution of formed clots. CONCLUSIONS: Contrary to popular perception, drug/polymer coatings do not inherently increase acute stent clotting; they reduce thrombosis. However, strut dimensions and positioning relative to the vessel wall are critical factors in modulating stent thrombogenicity. Optimal stent geometries and surfaces, as demonstrated with thin stent struts, help reduce the potential for thrombosis despite complex stent configurations and variability in deployment.

Factors influencing changes in articular cartilage following hemiarthroplasty in sheep.

This study examined the relationship between acetabular cartilage properties after hemiarthroplasty surgery and surgical variables including femoral head size and position. Nineteen sheep received unilateral hip arthroplasties and were euthanized one year post-operatively to harvest the femora and acetabula. Cartilage histology, biochemistry and material properties were determined from samples located in the superior load-bearing region. Femoral head size mismatch, leg length difference, anterior-posterior and medial lateral offset and anteversion were measured. In the acetabulum. substantial cartilage degradation occurred with widespread librillation and significant changes in the biochemical and material properties compared to the intact contralateral joint. Regression analyses on the surgical variables explained 75-80% of the changes in tissue biochemistry but did not explain the material changes. Head size mismatch and leg length difference were the most significant contributors of the five variables examined and therefore may be critical to successful outcome in hemiarthroplasty.