Vergleich aktiv und passiv beschichteter Stents im Hinblick auf Restenoseprophylaxe - eine vergleichende tierexperimentelle Studie

Background: Over the last years DES became more important in the treatment of coronary heart disease due to their superiority over BMS. Different DES have proven to be safe and are capable of reducing the complications occurring after BMS implantation such as in-stent restenosis and especially neointimaproliferation within the stent lumen, which is one of the major limitations in BMS usage. In the literature there are still two main limitations to the use of DES: There was evidence that DES still lead to restenosis in general and particularly to restenosis on the stent edges, which is known as the “candy-wrapper-effect”. Furthermore there are studies that showed that the neointimal coverage after DES implantation was not as good as expected possibly due to the anti-proliferative and immunosuppressant effects of the drugs used for the stent coating eventually leading to stent thrombosis. This study focuses on these limitations evaluating restenosis and neointimal coverage in the Camouflage®-Stent (passive coating) (Eucatech, Rheinfelden, Germany) and comparing the results with the Rapamycin (+ Camouflage®- Nanocoating)- DES (active + passive coating) (Eucatech, Rheinfelden, Germany). Material and Methods: Using 9 New Zealand White Rabbits 3 interventions took place. By inflating a balloon catheter in the target vessel and pushing it back and forth three times the induction of an arteriosclerotic plaque was performed. This process was supported by a 1%-cholesterol diet, which all laboratory animals received starting a week after intervention. Four weeks later a PCI was performed and the above mentioned stents were implanted in the superficial femoral arteries of the animal to dilate the induced stenosis. After another four weeks the animals were euthanized and the SFAs (superficial femoral arteries) were taken out for fixation in Technovit 9100 (Kulzer GmbH Wehrheim, Germany), which induces a chemical polymerization. The plastic blocs were thin-sectioned, polished and Giemsa stained so that the microscopic evaluation of the neointimal proliferation was possible. Results: Comparing the Camouflage®-Stent (passive coating) and Rapamycin (+ Camouflage®- Nanocoating)-DES (active + passive coating) we found significantly less intimaproliferation in the Rapamycin (763,2 mm²) coated stent than in the stent that was covered with Camouflage coating only (878,3 mm²) (p = 0.0088). We also took a closer look on the restenosis specifically on the stent edges and in the middle of the stent and found that there is significantly more restenosis on the stent edges for both groups (Camouflage p < 0,0001, Rapamycin p - 0,0006), but comparing the intimaproliferation on the stent edges between the two groups there was significantly less restenosis for the Rapamycin group ( p < 0,0001). The slightly increased restenosis in the middle of the Rapamycin stent was not significant (p - 0,2115). Furthermore we evaluated the stent strut coverage microscopically and found 26,89% naked stent struts and 3,361% extended overgrowth resulting in a thick neointima in the Rapamycin group, whereas in the Camouflage group there was missing stent coverage in 41,66% and extended overgrowth in 11,66%. Conclusion: On the basis of the results in this study, we conclude that the use of an actively and passively coated CoCr-Stent (Rapamycin (+ Camouflage®- Nanocoating)- DES) may reduce in-stent restenosis due to less intimaproliferation and may therefore lead to decreased in-stent thrombosis and improved healing in the vessel wall due to better strut coverage. But further evaluation will be necessary to state a general recommendation.