| Backgroud: "EXCEL" is a new kind of stent with rapamycin-coated and biodegradable polymer, different from the current drug-eluting stent (DES). Previous animal study and preliminary clinical observations showed that this stent could prevent neointimal proliferation and in-stent restenosis (ISR).Objective To evaluate the safety and long-term efficacy of the EXCEL stent for CAD, to examine the pathological changes of local stent segment of the vessels, and to investigate the probable mechanisms for anti-restenosis of EXCEL stent. Methods:1. Clinical study: Seventeen in-hospital patients (Male/femal=14/3) with CAD who had indications for coronary stenting were included. Patients received the same anti-platelet and anti-coagulation treatment. All the coronary angiography and stenting procedures were performed by the same members of a cardiac interventional team. Patients were followed up for at least 6 months. Quantitative coronary angiography (QCA) studies were performed at a mean (±SD) of (181.21±63.47) days. In-stent restenosis(ISR), late luminal loss(LLL), target lesion revascularization(TLR) and major adverse cardiac events(MACE) were documented.2. Laboratory study:Animal experiment: Twelve healthy dogs were randomized into EXCEL group (implanted EXCEL stents, n=6) or BMS group (implanted BMS stents, n=6). One of dogs was selected from every group randomly to be put to death after 24h. One of dogs was put to death at aspirin cessation for 2 weeks after aspirin therapy already for 3 months. The rest dogs were sacrificed at 3 month. Inorder to get the information of coronary anatomy and the coronary diameter of the target region, all the dogs accepted computed tomography angiography (CTA) before procedure and were fledged by common forage during the study. ECG and CAG were performed before stenting and being sacrificed. The rates of ISR, edge-restenosis, and dilated like aneurysm were recorded. We get the information of endothelialization, thenumber of vascular smooth muscle cells (VMSC) of neointimal, and the changes of VSMCs phenotypes by SEM and TEM. The structure of the vascular wall, the degree of neointimal hyperplasia from the compression of struts, the thickness, area of the neointimal, the cross-luminal area, and cells composition of the neointimal were detected by optical microscope. Results:1. Clinical results: There were no acute and sub-acute stent thrombosis occurred in patients treated by EXCEL stent during 6 months follow up. The rates of MACE, TLR, and ISR were 0. LLL is -0.02mm. There was no adverse reaction happened from rapamycin.2. Laboratory study: There was no restenosis in two groups. The thickness and area of the neointimal, and the cross-luminal area in EXCEL group and BMS group were (0.05±0.02)mm vs (0.13±0.05)mm> (0.42±0.12)mm2 vs (0.79+0. 15)mm2, and (2.63±0. 12)mm2 vs (2.38 + 0. 19)mm2 respectively, P<0.05;The inflammatory corpuscles in EXCEL group were less than those of in BMS group and most of them were lymphocytes. There was the similarity endothelialization in two groups. The degree of the neointimal hyperplasia was related to the degree of the pressure to the medial and external in two groups, the more pressure the more proliferative, and there was the same relation even though in the location of different distribution of stent struts. The shapes and disposition of the neoendtheliocytes were not the same in different locations of the stent struts in two groups in all 7 dogs (except the dog of thromobosis at 3 month and 2 week). The "slabstone-shaped" neoendtheliocytes were located in the surface of the struts or near to the struts. The "fusiform-shaped" neoendtheliocytes were located in the position of away from the struts. The macroaxis of the neoendtheliocytes had the same direction to blood stream in the location of straight line of the struts. The disposition of the neoendtheliocytes was "swirl-shaped" and there was no stationary relationship between the macroaxis of the neoendtheliocytes and the long axis of the vessel in the position of loop line of the struts. But there was no stent thrombosis in the 7 dogs. The medial and external in that dog with stent thrombosis were thinner than those of in other dogs.Conclusions:1. Clinical study: (1) There were no acute and sub-acute stent thrombosis occurred in patients treated by EXCEL stent. The rates of MACE, TLR, and ISR were zero during 6 months follow up. There was no adverse reaction happened from rapamycin. (2) It was safe and efficacy in the patients treated with EXCEL stent at least in 6 months.2. Laboratory study: (1) EXCEL stent was better than BMS in prevention of neointimal hyperplasia significantly in dog;the inflammation respons to local vessel was gentle. (2) The degree of the neointimal hyperplasia was related to the degree of the pressure to the medial and external and not related to the distribution of stent struts;the time to complete endothelialization in EXCEL stent was similarity to bare metal stent (BMS) and less than that of in sirolimus-eluting stent (SES). (3) There was no significant endothelialization delay in EXCEL stent, but it needs to be researched further to know the strength and the period of antiplatelet. (4) Our study showed that the shape and disposition of the neoendtheliocytes were not the same in different locations of the stent struts, but the mechanism and meaning were not clear. (5) It may be easy to be thrombosis in the location of stent due to displasia of the vessel.
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