Abstract： The first generation scaffolds of bare metal stents （BMS） and the second generation of drug eluting stents （DES） have been widely used in the treatment of coronary heart diseases. However, long term incidences of major adverse cardiovascular events and revascularization treatments are still high because of in-stent re-stenosis and thrombosis. These may be caused by chronic inflammations and vascular wall damages due to persistent metal stents stimulation. What’s more, the eluting drugs within metal stents could also disturb normal growth of vascular endothelial cell, intima, tunica media, smooth muscle and epimysium. Therefore, in order to meet these demands several fully biodegradable scaffolds and drug carried stents have been manufactured using polymers polyester, polycarbonate and polyphosphate, etc. Among them, the security and histo-and hemo-compatibilities of coronary scaffolds made from poly-lactic acid （PLA）, poly-glycolic acid（PGA）, chitosan as coating, poly-caprolactone （PCL） and other copolymer like poly-lactic-co-glycolic acid （PLGA） have been testified to be sound. Nevertheless, there exist several different shortages for these stents such as tensile strength deficiency and slow degradation. PLA is hard and brittle with slow degradation, while PGA is soft with insufficient support force and fast degradation. Whether stents degrade too fast or too slow, they could not supply sufficient strength and effective support after implantation, and also they may cause target vascular injuries and elastic shrink inducing restenosis and thrombosis in long terms. Using optimized molar ratio component of PLA and PGA with chitosan coating, we can get sound composite materials with better biocompatibility, moderate degradation （approximately 3 - 6 months of completedegradation）, adequate mechanical strength, lower inflammatory response and good range of extension, and establish an experiment ground for fully biodegradable vascular scaffolds fabrication.
Abstract:Objective To evaluate the effect of external stents on preventing vein graft neointima formation and medial thickening with non-restrictive macro porous polyester stent around porcine vein grafts. Methods Studies were performed by using ＂white race＂ pigs （n= 10） weight 25-30 kg. All the animals underwent bilateral saphenous vein into carotid artery bypass grafting. In each animal, a maeroporous stent was placed around a graft on one side and a control （unstented） graft on the opposite side. The polyester stent was shaped to cover both anastomoses completely. The size of the stem allowed unrestricted expansion of the graft in initial response to arterial pressure. After 35 days of surgery,all animals were taken to remove the grafts. Graft wall dimensions, platelet- derived growth factor （PDGF） expression and cell proliferation using proliferating cell nuclear antigen （PCNA） were measured on histological sections. Results Stents significantly reduced neointimal thickening （0. 4872 ± 0. 0706 mm vs. 0. 2259± 0. 0553mm,P〈0. 01）and medial thickening （0. 6246±0. 0859mm vs. 0. 4201±0. 0615mm,P〈0. 01）. Stents significantly reduced the percentage of cells expressing PDGF and PCNA. Media, intimal PCNA index was reduced from 7. 980/00± 4. 060/00 to 3.35±0.95%（P〈0.01）, PDGF index was reduced from 9.47%±5.35% to 2.67%± 0.97% （P 〈0. 01）. Conclusion External non-restrictive polyester stent can significantly inhibit neointimal formation and medial thickening, and may prevent late vein grafts restenosis.
Objective To systematically evaluate the efficacy and safety of sirolimus-eluting stents (SES) versus bare-metal stents (BMS) in treating patients with ST-segment elevation myocardial infarction. Methods The databases such as PubMed (1960 to Mar. 2011), EMbase (1980 to Mar. 2011), the Cochrane Central Register of Controlled Trials (1989 to Mar. 2011), CBM (1979 to Mar. 2011), VIP (1989 to Mar. 2011) and CNKI (1979 to Mar. 2011) were searched to collect all the randomized controlled trials (RCTs) on SES versus BMS in patients with ST-segment elevation myocardial infarction. After the data extraction and methodological quality evaluation, meta-analysis was conducted with RevMan 4.2 software. Results A total of 7 RCTs were included. Among 2 555 patients involved, 1 282 were in the SES group, while the other 1273 were in the BMS group. The results of meta-analyses showed that SES was superior to BMS in the target-lesion revascularization (OR=0.27, 95%CI 0.16 to 0.45, Plt;0.000 01) and target-vessel revascularization (OR=0.33, 95%CI 0.24 to 0.46, Plt;0.000 01). In contrast, there were no differences between SES and BMS in death, stent thrombosis and recurrence of myocardial infarction. Conclusion With the one-year clinical outcomes, SES is more effective than BMS in reducing the rate of target-vessel revascularization and target-lesion revascularization.
Objective To systematically review the efficacy and safety of different duration of dual antiplatelet therapies in patients undergoing new-generation drug-eluting stents implantation. Methods Such databases as MEDLINE, The Cochrane Library (Issue 2, 2015), EMbase, CBM, CNKI and WanFang Data were searched to collect studies on the different duration of dual antiplatelet therapies in patients undergoing new-generation drug-eluting stents implantation from inception to April 2015. Two reviewers independently screened literature, extracted data and assessed the risk of bias of included studies. Then, meta-analysis was performed using RevMan 5.3 software. Results Six trials were included. The results of meta-analysis showed: compared with 12 months dual antiplatelet therapy group, the incidence of bleeding in the 6 months dual antiplatelet therapy group was lower (OR=0.48, 95%CI 0.26 to 0.89, P=0.02). There were no significant differences in incidence of myocardial infarction, all cause mortality, stroke and stent thrombosis between two groups. Compared with 24 months dual antiplatelet therapy group, the incidence of stent thrombosis in the 12 months dual antiplatelet therapy group was higher (OR=2.50, 95%CI 1.13 to 5.61, P=0.02), but the incidence of bleeding in 12 months dual antiplatelet therapy group was lower (OR=0.25, 95%CI 0.07 to 0.89, P=0.03). No significant differences were found in the incidence of myocardial infarction, all cause mortality and stroke between 12 months dual antiplatelet therapy group and 24 months dual antiplatelet therapy group. Conclusions 6 months dual antiplatelet therapy following new-generation drug-eluting stent implantation is relatively more safe and efficacy. There is significant increase of incidence of bleeding in 12 or 24 months dual antiplatelet therapy. Due to the limited quantity and quality of included studies, the above results are needed to be validated by more high quality studies.
Coronary atherosclerotic heart disease is a serious threat to human life and health. In recent years, the main treatment for it is to implant the intravascular stent into the lesion to support blood vessels and reconstruct blood supply. However, a large number of experimental results showed that mechanical injury and anti-proliferative drugs caused great damage after stent implantation, and increased in-stent restenosis and late thrombosis risk. Thus, maintaining the integrity and normal function of the endothelium can significantly reduce the rate of thrombosis and restenosis. Stem cell mobilization, homing, differentiation and proliferation are the main mechanisms of endothelial repair after vascular stent implantation. Vascular factor and mechanical microenvironmental changes in implanted sites have a certain effect on re-endothelialization. In this paper, the process of injury caused by stent implantation, the repair mechanism after injury and its influencing factors are expounded in detail. And repairing strategies are analyzed and summarized. This review provides a reference for overcoming the in-stent restenosis, endothelialization delay and late thrombosis during the interventional treatment, as well as for designing drug-eluting and biodegradation stents.
In order to evaluate the safety performance of self-expandable NiTi alloy stents systematically, the dynamic safety factor drawn up by International Organization for Standardization, was used to quantitatively reflect the safety performance of stents. Based on the constitutive model of super-elastic memory alloy material in Abaqus and uniaxial tensile test data of NiTi alloy tube, finite element method and experiments on accelerated fatigue life were carried out to simulate the self-expansion process and the shape change process under the action of high and low blood pressure for three L-type stents of Φ8×30 mm, Φ10×30 mm, Φ12×30 mm. By analyzing the changes of stress and strain of self-expanding NiTi alloy stent, the maximum stress and strain, stress concentration position, fatigue strength and possible failure modes were studied, thus the dynamic safety factor of stent was calculated. The results showed that the maximum stress and plastic strain of the stent increased with the increase of grip pressure, but the maximum stress and strain distribution area of the stent had no significant change, which were all concentrated in the inner arc between the support and the connector. The dynamic safety factors of the three stents were 1.31, 1.23 and 1.14, respectively, which indicates that the three stents have better safety and reliability, and can meet the fatigue life requirements of more than 10 years, and safety performance of the three stents decreases with the increase of stent’s original diameter.
ObjectivesTo evaluate the efficacy and safety of four antiplatelet regimens after coronary drug-eluting stents by network meta-analysis.MethodsPubMed, The Cochrane Library, EMbase and Web of Science databases were electronically searched to collect randomized controlled trials (RCTs) of the comparison of different antiplatelet regimens after coronary drug-eluting stenting from inception to December 31st, 2019. Two reviewers independently screened literature, extracted data and assessed risk bias of included studies. Network meta-analysis was then performed by using Gemtc14.3 software, Stata16.0 software and RevMan5.3 software.ResultsA total of 23 RCTs involving 45 837 patients were included. The results of network meta-analysis showed that: in terms of prevention of myocardial infarction (MI) recurrence, the aspirin monotherapy after short-term dual antiplatelet therapy was inferior to the triple antiplatelet therapy (OR=2.13, 95%CI 1.08 to 4.03). In terms of reducing the incidence of ischemic compound events, the triple antiplatelet therapy was superior to the standard dual antiplatelet therapy (OR=0.53, 95%CI 0.39 to 0.72), the aspirin monotherapy after short-term dual antiplatelet therapy (OR=0.49, 95%CI 0.35 to 0.69) and the P2Y12 inhibitor monotherapy after short-term dual antiplatelet therapy (OR=0.51, 95%CI 0.35 to 0.73). There was no statistically significant difference among the four interventions in reducing the rate of in-stent thrombosis and all-cause mortality (P>0.05). In terms of safety, the bleeding rate of aspirin monotherapy after short-term dual antiplatelet therapy was lower than that of standard dual antiplatelet therapy (OR=0.70, 95%CI 0.55 to 0.86) and triple antiplatelet therapy (OR=0.58, 95%CI 0.36 to 0.90), and the bleeding rate of P2Y12 inhibitor monotherapy after short-term dual antiplatelet therapy was also lower than that of standard dual antiplatelet therapy (OR=0.51, 95%CI 0.39 to 0.65) and triple antiplatelet therapy (OR=0.43, 95%CI 0.26 to 0.67). The probability ranking diagram showed that: in terms of the recurrence rate of MI, the rate of in-stent thrombosis and the incidence of ischemic compound events, triple antiplatelet therapy was the lowest and aspirin monotherapy after short-term dual antiplatelet therapy was the highest. However, in terms of all-cause mortality and bleeding rate, aspirin or P2Y12 inhibitor monotherapy after short-term dual antiplatelet therapy was the lowest and triple antiplatelet therapy was the highest.ConclusionsThe available evidence suggests that when the risk of ischemia is low, we should choose aspirin or P2Y12 inhibitor monotherapy after short-term dual antiplatelet therapy, and P2Y12 inhibitor monotherapy may have a lower risk of ischemia and bleeding. When the risk of ischemia is high and bleeding is low, the triple or standard dual antiplatelet therapy should be selected, and the efficacy of triple antiplatelet therapy is superior, while the safety may be inferior.
Colorectal cancer is one of the common malignant tumor in the world, and about 57.6% of colorectal cancer surgical cases in our country are rectal cancer patients, which occupies a major proportion. Some patients with rectal cancer may already have emergencies such as intestinal obstruction or limited perforation at the time of consultation, which require immediate relevant treatment measures. Currently, there are multiple surgical and endoscopic treatment strategies available for obstructive and perforated rectal cancer. Surgeons need to perform an accurate and comprehensive assessment of the disease, define the goals of the current treatment, and formulate an appropriate treatment plan based on the patient’s clinical and oncological status in order to optimize the patient’s oncological outcome while minimizing the risk of complications associated with emergency colorectal surgery.