Drug-eluting stents and stent thrombosis: a cause for concern?

Drug-eluting stents, most commonly sirolimus-eluting stents and polymer-based paclitaxel-eluting stents, are now widely used during percutaneous coronary interventions, and have largely replaced bare-metal stents to treat a variety of native coronary artery and saphenous vein graft lesions. Stent thrombosis, a complication of both bare-metal and drug-eluting stents, is associated with significant morbidity and mortality including high rates of myocardial infarction and death. Recently, several studies in the literature have raised concern about increased rates of overall stent thrombosis and late stent thrombosis in drug-eluting stents in the so-called 'real world' where off-label uses of drug-eluting stents are common. Hypersensitivity reactions to the polymers used in drug-eluting stents, delayed endothelialization of the stents, and discontinuation of dual antiplatelet therapy have all been implicated in the pathophysiology of drug-eluting stents stent thrombosis. The incidence of total stent thrombosis as well as late stent thrombosis, however, does not seem to be significantly higher in drug-eluting stents than in bare-metal stents. An important risk factor for stent thrombosis in both types of stents appears to be the premature discontinuation of dual antiplatelet therapy, and physicians should educate their patients about the importance of adhering to dual antiplatelet therapy, given the dire clinical consequences of stent thrombosis.     

The conundrum of late and very late stent thrombosis following drug-eluting stent implantation

PURPOSE OF REVIEW: Drug-eluting stents reduce restenosis compared with bare metal stents, but there is growing concern that drug-eluting stents may lead to higher rates of late stent thrombosis, a rare and potentially catastrophic complication following stenting. RECENT FINDINGS: While the data on the risk of late stent thrombosis are not definitive, several general conclusions may be drawn from the available data. Late thrombosis, while associated with high mortality and morbidity, is an uncommon complication of both drug-eluting stents and bare metal stents. Randomized trials of approved drug-eluting stents versus bare metal stents have shown additional cases of late stent thrombosis in drug-eluting stents, but no significant difference in the cumulative incidence of stent thrombosis, myocardial infarction, or cardiac death at 4 years of follow-up. Observational studies suggest higher very late stent thrombosis incidence, but the relative risks of drug-eluting stents versus bare metal stents in specific high-risk groups require further study. Although the etiology of late stent thrombosis is multifactorial, premature discontinuation of clopidogrel appears to be the most important risk factor. SUMMARY: Long-term follow-up of patients after coronary stenting has identified stent thrombosis as a rare but serious event. Ongoing clinical trials in broader patient populations will be helpful to understand the risk of late stent thrombosis with greater certainty.     

Endoscopic management and prevention of migrated esophageal stents Martins BC,Retes FA,Medrado BF,Lima MS,Pennacchi CMPS,Kawaguti FS,简

The use of self-expandable metallic stents has increased recently to palliate inoperable esophageal neoplasia and also in the management of benign strictures. Migration is one of the most common complications after stent placement and the endoscopist should be able to recognize and manage this situation. Several techniques for managing migrated stents have been described, as well as new techniques for preventing stent migration. Most stents have a “lasso” at the upper flange which facilitates stent repositioning or removal. An overtube, endoloop and large polypectomy snare may be useful for the retrieval of stents migrated into the stomach. External fixation of the stent with Shim’s technique is efficient in preventing stent migration. Suturing the stent to the esophageal wall, new stent designs with larger flanges and double-layered stents are promising techniques to prevent stent migration but they warrant validation in a larger cohort of patients.     

Endoscopic management and prevention of migrated esophageal stents

The use of self-expandable metallic stents has increased recently to palliate inoperable esophageal neoplasia and also in the management of benign strictures. Migration is one of the most common complications after stent placement and the endoscopist should be able to recognize and manage this situation. Several techniques for managing migrated stents have been described, as well as new techniques for preventing stent migration. Most stents have a "lasso" at the upper flange which facilitates stent repositioning or removal. An overtube, endoloop and large polypectomy snare may be useful for the retrieval of stents migrated into the stomach. External fixation of the stent with Shim's technique is efficient in preventing stent migration. Suturing the stent to the esophageal wall, new stent designs with larger flanges and double-layered stents are promising techniques to prevent stent migration but they warrant validation in a larger cohort of patients.     

Airway stenting in Japan

Various types of outstanding airway stents have been made commercially available. In Japan, a total of 1004 airway stents (Dumon stents (Novatech, Aubagne, France), Gianturco Z stents (Cook Ins, Bloomington, USA), Ultraflex stents (Boston Scientific Corp, Natick, MA, USA), and Dynamic Y stents (Ruesch AG, Kernen, Germany)) were implanted from July 1991 until February 1998. Of all the various stents, the Dumon stent has become the standard worldwide. Also, the Dumon stent has been replacing the Gianturco Z stent as the preferred stent throughout Japan. The Dumon stent was the first stent covered by Japanese National Health Insurance. Therefore, we present our 5-year experience with the Dumon stent at our institution. In our experience, stenting is effective for the immediate and lasting relief of symptoms in patients with severe malignant obstruction of major airways.     

The future of esophageal endoprosthetics including the use of biodegradable materials

Endoscopic esophageal stent placement is an effective palliative treatment for malignant dysphagia and complications related to esophageal malignancies. Lately, esophageal stents have also been successfully used for benign indications including anastomotic stricture, iatrogenic perforation or leak, achalasia, fistula and to stabilize patients with esophageal variceal bleeding. At present, there are a wide variety of esophageal stents available to choose from; however, an ideal esophageal stent, which is both effective and without complications, has yet to be developed. Despite the evolution in this field, challenges such as stent migration, malignant tissue ingrowth, and recurrent stricture are some of the unsolved problems. In this article, we discuss about currently available esophageal stents including biodegradable stents, various stent materials, stent designs, indications for esophageal stent placement in treating both benign and malignant esophageal diseases, clinical outcomes, complications, novel esophageal stents including drug fiber coated stents, dynamic esophageal stents, and the future direction of esophageal endoprosthetics.     

Stenting and interventional radiology for obstructive jaundice in patients with unresectable biliary tract carcinomas

Together with biliary drainage, which is an appropriate procedure for unresectable biliary cancer, biliary stent placement is used to improve symptoms associated with jaundice. Owing to investigations comparing percutaneous transhepatic biliary drainage (PTBD), surgical drainage, and endoscopic drainage, many types of stents are now available that can be placed endoscopically. The stents used are classified roughly as plastic stents and metal stents. Compared with plastic stents, metal stents are of large diameter, and have long-term patency (although they are expensive). For this reason, the use of metal stents is preferred for patients who are expected to survive for more than 6 months, whereas for patients who are likely to survive for less than 6 months, the use of plastic stents is not considered to be improper. Obstruction in a metal stent is caused by a tumor that grows within the stent through the mesh interstices. To overcome such problems, a covered metal stent was developed, and these stents are now used in patients with malignant distal biliary obstruction. However, this type of stent has been reported to have several shortcomings, such as being associated with the development of acute cholecystitis and stent migration. In spite of these shortcomings, evidence is expected to demonstrate its superiority over other types of stent.     

Uncovered Hanaro Versus Luminex metal stents for palliation of malignant biliary strictures

BACKGROUND: Endoscopic stent insertion is the optimum method of palliation for malignant biliary obstruction. Various types of self-expanding metal stents have been introduced in the market. Whether one type of stents is superior to the others in terms of stent patency remains undefined. GOALS: This randomized trial compared 2 uncovered metal stents with similar technical characteristics, but significant cost difference, in the palliation of inoperable malignant biliary strictures. STUDY: Ninety-two patients with inoperable biliary obstruction were randomized to receive either a 10-mm diameter Hanaro or Luminex uncovered metal stent. The duration of stent patency, the overall patient survival, the mechanism of stent occlusion, and the adverse events were analyzed. RESULTS: Eighty-nine patients were included in the analysis; 44 received Hanaro stents and 45 Luminex stents. The overall median patency rates between the 2 stents did not differ (328 d for the Hanaro vs. 289 d for the Luminex stent; P=0.815). Similarly, no difference was found between the overall median survival rates by the 2 stents (347 d for the Hanaro vs. 307 d for the Luminex stent; P=0.654). Two major procedure-related complications occurred, perforation (Hanaro stent) and proximal stent migration (Luminex stent). Stent occlusion requiring reintervention occurred in 25 patients (11 with the Hanaro vs. 14 with the Luminex stent; P=0.521). CONCLUSIONS: The 2 uncovered metal stents are comparable in terms of placement, occlusion rates, overall stent patency, and patient survival; Hanaro stent insertion, however, seems to be a cost-saving strategy at least in Greece.     

The paclitaxel-eluting stent in percutaneous coronary intervention: Part II. Comparison with the sirolimus-eluting stent, economics, and unanswered questions

The paclitaxel- and sirolimus-eluting stents are currently the only drug-eluting stents approved for use in the United States. These 2 stents differ in terms of mechanism of drug action, the construct of the stent itself, and the drug delivery polymer. Clinical trials have demonstrated superiority of both paclitaxel- and sirolimus-eluting stents when compared with bare-metal stents in terms of reducing restenosis and the need for target vessel revascularization. Recently published head-to-head trials have not conclusively shown 1 drug-eluting stent to be superior to the other, but have demonstrated more favorable angiographic results with the sirolimus-eluting stent compared with the paclitaxel-eluting stent; however, no significant difference has been demonstrated in clinical outcomes such as myocardial infarction or death. In terms of economics, the paclitaxel-eluting stent is substantially more expensive than the bare-metal stent. However, by significantly reducing the risk of restenosis and need for repeat revascularization, the higher direct cost of the paclitaxel-eluting stent may in theory be offset by lower overall healthcare costs, although economic analyses have yet to definitively establish that the paclitaxel-eluting stent is truly cost-effective. There is still much to be discovered regarding the paclitaxel-eluting stent, specifically the optimal stent design and drug release mechanism, the relative safety and efficacy of the paclitaxel-eluting stent compared with other drug-eluting stents, the long-term effects of the paclitaxel-eluting stent, the ideal antiplatelet regimen to use in patients with a paclitaxel-eluting stent, the safety and efficacy of the paclitaxel-eluting stent in various high-risk patient groups, and the ultimate cost-effectiveness of this device.     

Intravascular ultrasound observations during iliac stent deployment.

BACKGROUND: To evaluate the role of intravascular ultrasound (IVUS) during iliac stent deployment, with comparison of four major types of iliac stents. METHODS: Thirty-eight iliac arteries of 37 patients were observed with intravascular ultrasound after implantation of various stents including Palmaz stents in 10, Memotherm stents in 11, Wallstent in 10, and Strecker stents in 7. Quantitative measurements on ultrasound included the ratio of the short-axial to the long-axial diameters of the stent (symmetry index), the ratio of stent cross-sectional area to that of the reference lumen (expansion index), and stent-to-wall apposition. RESULTS: Intravascular ultrasound revealed significant differences among four major types of iliac stent, in spite of satisfactory angiographic appearances in all patients. It demonstrated significant deformity of the Strecker stent (symmetry index of 0.76-0.09) compared with other stents. The Memotherm stent and the Palmaz stent were superior to other stents in terms of degree of expansion (mean expansion index of 0.87 and 0.82 respectively). Stent cross-sectional area greater than 80% of the reference lumen could be sufficient for iliac stent deployment. The Palmaz stent was superior to other stents in terms of stent-to-wall apposition. CONCLUSIONS: Intravascular ultrasound can provide precise and useful cross-sectional morphological and quantitative information in terms of stent configuration, degree of stent expansion, and stent-to-wall apposition.     

Incidence and risk factors for biliary and pancreatic stent migration.

Endoprostheses are commonly used in the treatment of biliary and pancreatic disorders. The frequency of and potential risk factors for stent migration, however, remain largely unknown. From January 1986 to June 1990, 807 biliary and pancreatic stents were placed at our institution. Our study analyzed the occurrence of stent migration among the 589 stents for which follow-up data were available. Results demonstrated incidence rates of 4.9 and 5.9% for proximal (into the duct) and distal (out of the duct) biliary stent migration, respectively. Likewise, incidence rates of 5.2 and 7.5% were observed for proximal and distal pancreatic stent migration, respectively. Malignant strictures, larger diameter stents, and shorter stents were significantly associated with proximal biliary stent migration. Sphincter of Oddi dysfunction and longer stents were associated with proximal pancreatic stent migration. Migration of stents out of the common bile duct occurred more frequently in papillary stenosis. No other significant risk factors for distal migration were found. These results indicate that stent migration is an important complication. Multiple risk factors were associated with stent migration and need to be considered in the development of new stent types.     

支架携带放射性核素能力的实验研究

目的携带放射性核素32P的支架是实施冠状动脉(冠脉)局部放射治疗以预防再狭窄的重要方法之一。本研究采用一种新的支架包被方法,以评价其携带放射性核素的能力。方法自行研制的四种核素32P支架血浆包被32P支架、明胶包被32P支架、32P直接涂层支架、32P静脉包被支架。每种6支,均含32P胶体10μCi。置于压力为90mm?Hg的流水管中冲洗。冲洗前和冲洗后1、4、14、21d各取1支架测定放射活度。放射性包被支架制作的同时,留置5份5μCi32P胶体液作为自然衰减对照品,于1、4、7、14、21d后各取1份32P胶体液,测定其放射活度。4只犬每只犬冠脉内置入同样方法制成的血浆包被32P支架2个,于术前和术后1d、2周、7周、10周测定放射活度。3只犬冠脉内置入自体静脉包被32P支架1个,于术后1、2、3个月测定放射活度。结果流水冲洗实验示四种支架冲洗前携带32P放射活度分别为4.81、4.32、1.96、4.82μCi,冲洗21天后放射活度分别为0.33、0.12、0.01、1.34μCi,血浆和静脉包被支架时间-放射活度变化曲线接近于自然衰减曲线。冠脉置入支架实验示4条犬每只犬均成功置入血浆包被32P支架1个,术后1天、17天、7周、10周支架残留的放射活度分别为4.98、1.71、0.52、0.09、0.03μCi;3只犬中1只犬成功置入1个静脉包被32P支架,70天处死测定其放射活度为0.3μCi。结论血浆和静脉包被支架均有较好的携带核素能力,抗冲洗能力强。血浆包被支架制备简便,置入冠脉可行,置入机体可达到有效治疗剂量。     

Improved technique for use of half-stents remounted on a stent delivery system

The use of half-length intracoronary Johnson & Johnson stents has been described in a number of settings. Half-stents are useful for very short lesions, avoidance of bifurcations or side-branches, ostial stenosis, covering gaps between adjacent stents, and for dissection adjacent to stents caused by postdilatation. Previously described methods for use of half-stents have involved bare stents, or significant manipulation of either the stent or the delivery sheath for remounted half-stents. We describe a method for half-stent preparation and delivery that does not involve distortion of the stent or the delivery sheath. The risk of stent loss, as can occur with bare stents, is diminished. The geometry of the stent is preserved since it is not expanded and then recrimped, and the end of the delivery sheath is not flared or distorted, which may interfere with stent delivery. © 1996 Wiley-Liss, Inc.     

Long-term effect of stent placement in 115 patients with Budd-Chiari syndrome

AIM: To report the long-term effect of stent placement in 115 patients with Budd-Chiari syndrome (BCS).METHODS: One hundred and fifteen patients with BCS were treated by percutaneous stent placement. One hundred and two patients had IVC stent placement, 30 patients had HV stent placement, 17 of them underwent both IVC stent and HV stent. All the procedures were performed with guidance of ultrasound.RESULTS: The successful rates in placing IVC stent and HV stent were 94 % (96/102) and 87 % (26/30), respectively.Ninety-seven patients with 112 stents (90 IVC stents, 22 HV stents) were followed up. 96.7 %(87/90) IVC stents and 90.9 %(20/22) HV stents remained patent during follow up periods (mean 49 months, 45 months, respectively). Five of 112 stents in the 97 patients developed occlusion. Absence of anticoagulants after the procedure and types of obstruction (segmental and occlusive) before the procedure were related to a higher incidence of stent occlusion.CONCLUSION: Patients with BCS caused by short length obstruction can be treated by IVC stent placement, HV stent placement or both IVC and HV stent placement depending on the sites of obstruction. The long-term effect is satisfactory.Anticoagulants are strongly recommended after the procedure especially for BCS patients caused by segmental occlusion.     

Stent placement for benign colonic stenosis: case report,review of the literature,and animal pilot data

BACKGROUND: Permanent metal stent placement for malignant intestinal obstruction has been proven to be efficient. Temporary stents for benign conditions of the colon and rectum are less studied. This is a case study, review of the literature, and observation from an animal model on placement of stents in the colorectum for benign disease. MATERIALS AND METHODS: A 55-year-old man presented with recurrent obstructions from a benign stricture of the distal sigmoid colon. After failed balloon dilations, a polyester coated stent was placed. The purpose of the stent was to improve symptoms and avoid surgery. The stent was expelled after 5 days. We conducted a literature review of stents placed for benign colorectal strictures and an animal study to evaluate stent migration. RESULTS: In the literature, there were 53 reports of uncovered metal stents, four covered metal stents, and six polyester stents. Patency rates were 71%, and migration rate was 43%. Migration occurred earlier with polyester stents (mean = 8 days) versus covered (32 days) or uncovered metal stents (112 days). Severe complications were seen in 23% of patients. Four 45-kg pigs underwent rectosigmoid transection with a 21-mm anastomosis and endoscopic placement of a Polyflex stent. Two stents were secured with suture. Stents without fixation were expelled within 24 h of surgery. Stents with fixation were expelled between postoperative days 2 and 14. CONCLUSION: Stents for the treatment of benign colorectal strictures are safe, with comparable patency rates between stent types. Metal stents can cause severe complications. In a pig model, covered polyester stents tend to migrate early even with fixation. Further investigation needs to focus on new stent designs and/or better fixation.     

Comparison of clinical and angiographic outcomes between S670 and NIR stents

OBJECTIVES: This study evaluated the long-term outcomes of successfully implanted S670 and NIR stents. METHODS: Stents were successfully implanted in 143 patients (148 lesions) aged 65 +/- 9 years from January 1999 to April 2001. Sixty-eight lesions were treated with S670 stents and 80 with NIR stents. Quantitative coronary angiography was performed before, immediately after and 6 months after implantation. An angiographic classification of in-stent restenosis was developed according to the geographic distribution of intimal hyperplasia in reference to the implanted stent. Furthermore, the relationships between stent diameter and length and restenosis rate were estimated. RESULTS: Type B2/C lesions were significantly more common in patients with S 670 (77.3%) stents compared with NIR (43.6%). Stent length was longer and diameter was smaller in patients with S 670 stents compared with those with NIR stents. Acute-gain was similar in the two groups, but late-loss was significantly greater in patients with S 670 stents compared with those with NIR stents. Restenosis rate and target lesion revascularization rate were similar in the two groups. The diffuse type of restenosis lesion was frequently found in S 670 stents. The stent diameter, but not stent length, influenced the restenosis rate in S 670 stents. Both stent length and diameter influenced the restenosis rate in NIR stents. CONCLUSIONS: Late-loss was larger and in-stent restenosis of diffuse type was significantly greater in S 670 stents compared with NIR stents. However, stent length was significantly longer and type B2/C lesions were significantly greater in S 670 stents compared with NIR stents. There was no difference in restenosis rate and target lesion revascularization rate. In addition, restenosis rate was not influenced by stent length in S 670 stents, so S 670 stents may be useful for complex lesions.     

Randomized trial of paclitaxel- and sirolimus-eluting stents in small coronary vessels.

AIMS: Sirolimus- and paclitaxel-eluting stents effectively reduce restenosis in small coronary vessels. The relative efficacy of these drug-eluting stents in this high-risk subset is not known. METHODS AND RESULTS: A total of 360 patients undergoing percutaneous coronary intervention for de novo lesions in native coronary vessels with a diameter of <2.80 mm received randomly paclitaxel-eluting stents (n=180) or sirolimus-eluting stents (n=180). The primary endpoint was in-stent late luminal loss. Secondary endpoints were angiographic restenosis and need of target lesion revascularization. The study intended to show that the paclitaxel-eluting stent is not inferior to the sirolimus-eluting stent with respect to the primary endpoint. The non-inferiority margin was set at 0.16 mm. Follow-up angiography was performed in 87% of the patients. In-stent late luminal loss in the paclitaxel-eluting stent group was 0.32 mm (upper 95% boundary, 0.42 mm), which was greater than that in the sirolimus-eluting stent group, failing to show the non-inferiority of the paclitaxel-eluting stent to the sirolimus-eluting stent (P>0.99). Angiographic restenosis was found in 19.0% of the lesions in the paclitaxel-eluting stent group and 11.4% of the lesions in the sirolimus-eluting stent group (P=0.047). Target lesion revascularization was performed in 14.7% of the lesions treated with paclitaxel-eluting stents and 6.6% of the lesions treated with sirolimus-eluting stents (P=0.008). CONCLUSION: The paclitaxel-eluting stent is associated with a greater late luminal loss and is less effective in reducing restenosis in small coronary vessels than the sirolimus-eluting stent.     

Trimming of a migrated metal stent for malignant colonic stricture using argon plasma coagulation

We report the first case of trimming of a migrated metal colonic stent for stent induced severe anorectal pain. We present a case of a 54-year-old female with history of metastatic colorectal carcinoma who had stent placement secondary to obstruction. Subsequent distal migration of the stent caused ulcerations into the rectal mucosa and excruciating anorectal pain. We used argon plasma coagulation (APC) to successfully trim the exposed distal portion of the metal stent and rat tooth forceps to retrieve the stent fragments. The use of APC for trimming metallic stents is an effective procedure that can be used to trim migrated rectal stents that result in significant rectal pain. To date, few studies have been published that use APC to trim metallic stents placed in the gastrointestinal tract. To the best of our knowledge, ours is the only known case in which the indication for stent trimming was severe stent induced rectal pain. The procedure resulted in complete relief of patient symptoms. Therefore, APC is a safe and effective way to trim colo-rectal stents to definitively relieve the symptom of stent induced rectal pain in patients who have experienced distal stent migration and mucosal ulceration.     

Late distortion of the original Palmaz stent implanted in postoperative lesions associated with congenital heart disease.

The objective of this study was to report late distortion of a Palmaz stent. Late distortion of an original Palmaz stent, implanted in an extracardiac lesion, is rare. We completed a 1-year follow-up of 54 patients who had been implanted with 80 Palmaz stents in extracardiac lesions. Distortion of two stents was detected in two patients. For case 1, we implanted a P188 stent for supravalvar pulmonary stenosis complicating an arterial switch operation in a 14-year-old girl. Seven months later, we found compression of the stent. Although we implanted two P308 stents anterior to the distorted stent, distortion of both stents developed after 1 month. Two more P308 stents placed inside each stent were gradually recompressed. A CAT scan showed compression of the stent by a dilated sinus of valsalva. For case 2, we implanted a P308 stent for stenosis of the superior vena cava after Williams operation in an 11-year-old boy. A chest X-ray documented longitudinal compression of the stent 27 months after implantation and a CAT scan showed the ascending aorta was in contact with the stent. A Palmaz stent may be distorted when implanted in a lesion adjacent to a pulsating aorta.     

64层螺旋CT冠状动脉支架成像效果的影响因素

目的 探讨64层螺旋CT冠状动脉支架成像效果的影响因素.方法选取冠状动脉药物涂层金属支架植入术后行64层螺旋CT检查的病例116例,对支架部位图像质量采取半定量评价,分析支架直径、支架长度、支架材质、支架个数和钙化情况对支架部位CT图像质量的影响.结果 64层螺旋CT检出有意义支架内再狭窄的敏感度、特异度、阳性预测值、阴性预测值分别为85.7%、90.2%、60.0%、97.4%.直径2.75 mm以上支架的CT图像质量优于直径2.75 mm及以下的支架(P<0.001),非钙化病变的支架术后CT图像质量优于钙化病变(P<0.05).支架长度、支架材质和是否多支架对支架部位CT图像质量无影响.结论 64层螺旋CT能胜任冠状动脉支架术后复查.直径2.75 mm以上支架和非钙化病变的支架病例更适合用64层螺旋CT进行复查.