Increasing arterial wall injury after long-term implantation of two types of stent in a porcine coronary model.

Aims: There is increased late loss in luminal diameter following long-term coronary stenting, compared with balloon angioplasty. We evaluated short- and long-term vessel wall injury after experimental implantation of two stent designs as well as balloon angioplasty and their relationship to neointimal hyperplasia.
Methods and Results: Wiktor stents and Palmaz-Schatz stents were implanted in normal coronary arteries of pigs (balloon/artery ratio: 0.9-1.1). In control coronary arteries, balloon angioplasty was performed. At 1, 4 and 12 weeks, the vessel injury score, neointimal thickness and inflammatory response were assessed by histology. The vessel injury score increased over time in both Wiktor and Palmaz-Schatz stents: 0.9 +/- 0.1, 1.5 +/- 0.5 and 1.7 +/- 0.6 (mean +/- SD) for Wiktor stents and 0.7 +/- 0.2, 1.0 +/- 0.1 and 1.2 +/- 0.3 for Palmaz-Schatz stents at 1, 4 and 12 weeks follow-up, respectively. No increase in injury was seen in balloon angioplasty controls. Inflammation was seen in both stented groups but was absent 12 weeks after balloon angioplasty. No strong correlation between injury and neointimal thickness was apparent.
Conclusion: Stents induce chronic injury in contrast to balloon angioplasty. Stent design (coil vs slotted tube) as well as inflammation may influence vessel response.