Covered stents: A review

Expanded Polytetrafluoroethylene Membranes for Vascular Stent Coating: Manufacturing, Biomedical and Surgical Applications, Innovations and Case Reports

Coated stents are defined as innovative stents surrounded by a thin polymer membrane based on polytetrafluoroethylene (PTFE)useful in the treatment of numerous vascular pathologies. Endovascular methodology involves the use of such devices to restore blood flow in small-, medium- and large-calibre arteries, both centrally and peripherally. These membranes cross the stent struts and act as a physical barrier to block the growth of intimal tissue in the lumen, preventing so-called intimal hyperplasia and late stent thrombosis. PTFE for vascular applications is known as expanded polytetrafluoroethylene (e-PTFE) and it can be rolled up to form a thin multilayer membrane expandable by 4 to 5 times its original diameter. This membrane plays an important role in initiating the restenotic process because wrapped graft stent could be used as the treatment option for trauma devices during emergency situations and to treat a number of pathological vascular disease. In this review, we will investigate the multidisciplinary techniques used for the production of e-PTFE membranes, the advantages and disadvantages of their use, the innovations and the results in biomedical and surgery field when used to cover graft stents.

Engineering biomaterials to prevent post-operative infection and fibrosis

Implantable biomaterials are essential surgical devices, extending and improving the quality of life of millions of people globally. Advances in materials science, manufacturing, and in our understanding of the biological response to medical device implantation over several decades have resulted in improved safety and functionality of biomaterials. However, post-operative infection and immune responses remain significant challenges that interfere with biomaterial functionality and host healing processes. The objectives of this review is to provide an overview of the biology of post-operative infection and the physiological response to implanted biomaterials and to discuss emerging strategies utilizing local drug delivery and surface modification to improve the long-term safety and efficacy of biomaterials.

Surgical management of iatrogenic coronary artery perforations: when percutaneous treatment fails

Coronary perforation is a rare complication of percutaneous coronary interventions and a challenging scenario which imposes prompt recognition and treatment. Although it may be successfully managed percutaneously, a surgical treatment may be preferable in some cases. We report the case of a patient with a coronary perforation with initial percutaneous treatment complicated with extravascular implantation of a covered stent and liver laceration, who was succesfully treated by cardiac surgery. This case suggests the importance of the proximity of an onsite cardiac surgery center when complex coronary artery percutaneous interventions are performed in hospitals with offsite surgical support.

Promising polymeric compounds for coronary stent graft membrane

The literature review discusses the studies on developing the polymer membrane of a coronary stent graft. The new generation of coronary stent grafts is designed to increase the hemocompatibility and ensure its delivery to poorly accessible artery regions. Based on the clinical use results, three groups of promising polymers were identified: biostable polyurethanes, polyvinyl alcohol-based cryogels, bioresorbable compositions based on polylactide-caprolactone and lactic acid-glycolic acid copolymer. However, the possibility of their clinical application requires further experimental studying.

Covered Stenting Is an Effective Option for Traumatic Carotid Pseudoaneurysm with Promising Long-Term Outcome

Objective

Covered stenting is an optional strategy for traumatic carotid pseudoaneurysm, especially in malignant conditions of potential rupture, but the long-term outcomes are not clear. Our aim was to determine if covered stenting is an effective option for traumatic carotid pseudoaneurysm with promising long-term outcomes.

Methods

Self-expanding Viabahn and balloon-expandable Willis covered stents were separately implanted for extra- and intracranial traumatic carotid pseudoaneurysm. The covered stent was placed across the distal and proximal pseudoaneurysm leakage under roadmap guidance. Procedural success was defined as technical success (complete exclusion of the pseudoaneurysm and patency of the parent artery) without a primary end point (any stroke or death within 30 days after the procedure). Long-term outcomes were evaluated as ischemic stroke in the territory of the qualifying artery by clinical follow-up through outpatient or telephone consultation and as the exclusion of the pseudoaneurysm and patency of the parent artery by imaging follow-up through angiography.

Results

Five patients with traumatic carotid pseudoaneurysm who underwent covered stenting were enrolled. The procedural success rate was 100%. No ischemic stroke in the territory of the qualifying artery was recorded in any of the five patients during a mean clinical follow-up of 44±16 months. Complete exclusion of the pseudoaneurysm and patency of the parent artery were maintained in all five patients during a mean imaging follow-up of 39±16 months.

Conclusion

Satisfactory procedural and long-term outcomes were obtained, suggesting that covered stenting is an effective option for traumatic carotid pseudoaneurysm.

Emergency management of iatrogenic arterial injuries with a low-profile balloon-expandable stent-graft: Preliminary results

Endovascular treatment of arterial injuries with stent-graft is a reliable alternative approach in patients not suitable for embolization or at high risk for surgery. The aim of our study was to evaluate the efficacy and the safety of the BeGraft stent-graft, a low-profile balloon expandable covered stent, for emergency endovascular treatment of iatrogenic arterial injuries.Between August 2015 and September 2018, 34 consecutive patients (mean age 71 ± 12 years, 9 females) underwent implantation of BeGraft stent-grafts for iatrogenic arterial injuries (22 active bleedings, 11 pseudoaneurysms, and 1 enteric-iliac fistula). The primary endpoints were technical and clinical success and rates of major and minor complications. The secondary endpoint was the patency of the device during the follow-up. Imaging follow-up was performed by duplex ultrasound and/or computed tomography angiography (according to lesion site/target vessel), at 1-6-12-15 and 24 months.In all 34 patients (100%), the lesion or the defect was effectively excluded with a cumulative amount of 42 stent-grafts. The clinical success was documented in 30/34 patients (88.2%). Neither device- or procedure-related deaths, or major complications occurred. A minor complication was reported in 1 patient (2.9%), successfully treated during the same procedure. Thirty (88.2%) patients were available for a mean follow-up time of 390 ± 168 days (minimum 184, maximum 770), with no observed loss of patency, yielding a 100% Kaplan-Meier cumulative survival patency function. The percentage of patent patients was 30/30 at 6 months, 22/22 at 12 months, and 5/5 at 15 months.Endovascular treatment of iatrogenic arterial injuries with the BeGraft stent-graft is minimally invasive and effective, with good patency rate at midterm follow-up.

A review of endovascular stenting for superior vena cava syndrome in fibrosing mediastinitis

Fibrosing mediastinitis (FM) is a rare disorder of inflammation and fibrosis involving the mediastinum. The formation of fibroinflammatory mass in the mediastinum can lead to obstruction of mediastinal structures and cause severe debilitating and life-threatening symptoms. Superior vena cava syndrome (SVCS) is a dreaded complication of FM with no medical therapy proven to be efficacious. Spiral vein grafting has long been utilized as first-line therapy for SVC syndrome due to FM. Endovascular repair with stents and angioplasty for malignant causes of SVC syndrome is well established. However, there are limited data on their utility in SVC syndrome due to FM. We present two cases of SVC syndrome due to FM treated with endovascular stenting and a detailed review of current literature on its utility in SVCS due to benign causes.

Single Center 7 Year Experience of Coronary Artery Perforation: Angiographic and Procedural Characteristics, Management and Outcome

Context:

Coronary artery perforation is a rare but potentially catastrophic complication of percutaneous coronary intervention (PCI). It is infrequent complication of PCI.

Aims:

The objective of the study is to report the 7-year experience of coronary artery perforation with respect to incidence, clinical and angiographic characteristics, management and outcomes.

Settings and Design:

The study involved retrospective analysis of single centre 7 years of percutaneous coronary intervention data. Patients who had complication of coronary artery perforation during PCI were identified and included in the study.

Subjects and Methods:

Retrospective analysis of clinical, angiographic and procedural characteristics as well as management and outcome of coronary artery perforation was done.

Statistical Analysis Used:

The whole data were tabulated, variables were presented as mean and percentages and comparison was done within them.

Results:

A total of 37 cases of coronary artery perforation were identified from 4532 PCI performed. Most of the coronary artery perforation belonged to Ellis Type II and Type III (both n = 15) followed by Type III CS and Type I. Lesions belonged to AHC/AHA Type C in 31 cases. Most frequent mechanism of coronary artery perforation was related to the use of guidewire and balloon (both n = 17). The total of 8 cases presented with cardiac tamponade requiring pericardiocentesis. Eleven cases required emergency covered stent implantation. In two cases microcoil was used while one case required polyvinyl alcohol particles to seal the perforation site. There was no in-hospital mortality while 30-day mortality occurred in one patient. One case was referred for emergency surgery.

Conclusions:

Coronary artery perforation is rare but potentially fatal complication of percutaneous coronary intervention. Complication of coronary artery perforation can be managed effectively in the catheterization laboratory without the need of emergency of bailout surgery and in-hospital outcomes remain good in the majority of cases.

Comparison of Covered Versus Uncovered Stents for Benign Superior Vena Cava (SVC) Obstruction

PURPOSE

To identify whether long-term symptom relief and stent patency vary with the use of covered versus uncovered stents for the treatment of benign SVC obstruction.

METHODS AND MATERIALS

We retrospectively identified all patients with benign SVC syndrome treated to stent placement between January 2003 and December 2015 (n = 59). Only cases with both clinical and imaging follow-up were included (n = 47). In 33 (70%) of the patients, the obstruction was due to a central line or pacemaker wires, and in 14 (30%), the cause was fibrosing mediastinitis. Covered stents were placed in 17 (36%) of the patients, and 30 (64%) patients had an uncovered stent. Clinical and treatment outcomes, complications, and the percent stenosis of each stent were evaluated.

RESULTS

Technical success was achieved in all cases at first attempt. Average clinical and imaging follow-up in years was 2.7 (range 0.1-11.1) (covered) and 1.7 (range 0.2-10.5) (uncovered), respectively. There was a significant difference (p = 0.044) in the number of patients who reported a return of symptoms between the covered (5/17 or 29.4%) and uncovered (18/30 or 60%) groups. There was also a significant difference (p = < 0.001) in the mean percent stenosis after stent placement between the covered [17.9% (range 0-100) ± 26.2] and uncovered [48.3% (range 6.8-100) ± 33.5] groups. No significant difference (p = 0.227) was found in the time (days) between the date of the procedure and the date of clinical follow-up where a return of symptoms was reported [covered: 426.6 (range 28-1554) ± 633.9 and uncovered 778.1 (range 23-3851) ± 1066.8]. One patient in the uncovered group had non-endovascular surgical intervention (innominate to right atrial bypass), while none in the covered group required surgical intervention. One major complication (SIR grade C) occurred that consisted of a pericardial hemorrhagic effusion after angioplasty that required covered stent placement. There were no procedure-related deaths.

CONCLUSION

Both covered and uncovered stents can be used for treating benign SVC syndrome. Covered stents, however, may be a more effective option at providing symptom relief and maintaining stent patency if validated by further studies.

Clinical Outcomes of Polytetrafluoroethylene-Covered Stents for Coronary Artery Perforation in Elderly Patients Undergoing Percutaneous Coronary Interventions

Background

Coronary artery perforation (CAP) during percutaneous coronary intervention (PCI) is associated with increased mortality. Polytetrafluoroethylene covered stents (CS) are an effective approach to treat CAP, but data regarding elderly patients requiring CS implantation for CAP are limited. The aim of this study is to report clinical data for elderly CAP patients undergoing CS implantation during PCI.

Methods

Nineteen consecutive elderly patients (≥ 65 years) undergoing CS implantation due to PCI-induced CAP in a tertiary referral center from July 2003 to April 2016 were retrospectively examined.

Results

There were 13 men and six women, with a mean age of 75.3 ± 5.6 years (range: 65-86 years). Perforation grade was Ellis type II in five patients (26.3%), and Ellis type III in 14 patients (73.7%). Cardiac tamponade developed in six patients (31.6%), and intra-aortic balloon pumping was needed in four patients (21.1%). The overall success rate for CS implantation rate was 94.7%. The overall in-hospital mortality rate was 15.8%; the in-hospital myocardial infarction rate was 63.2%. Among 16 survival-to-discharge cases, dual antiplatelet therapy (DAPT) was prescribed in 14 cases (87.5%) for a mean duration of 14 months. Overall, there were five angiogram- proven CS failures among 18 patients receiving successful CS implantation. The 1, 2 and 4 years of actuarial freedom from the CS failure were 78%, 65%, and 43% in the angiogram follow-up patients.

Conclusions

CS implantation for CAP is feasible and effective in elderly patients, while CS failure remains a major concern that encourages regular angiographic follow-up in these case.

Successful Treatment of Iatrogenic External Iliac Artery Perforation With Covered Stent: Case Report and Review of the Literature

Retroperitoneal hemorrhage from iliac artery injury is a potentially serious complication of vascular interventional procedures leading to hemorrhagic shock and death if not diagnosed early and treated promptly. We report a 70-year-old male admitted to our facility with non-ST-elevation myocardial infarction, whose heart catheterization revealed left anterior descending artery (LAD) with 80% proximal, 95% mid and 100% distal disease. The left circumflex and right coronary arteries were 100% occluded proximally and received collaterals from the LAD. The patient declined coronary artery bypass surgery; therefore, the decision was made to perform high-risk percutaneous coronary intervention (PCI) of the LAD with Impella left ventricular assist device support. Left femoral artery angiogram revealed severely tortuous and calcified aorta, left external iliac and left common iliac arteries, and was accessed with 14-inch Impella sheath. He developed groin pain with mild hypotension thought to be due to sedation, which responded to intravenous fluids and dopamine. He underwent successful rotational atherectomy of the proximal and mid LAD with deployment of drug-eluting stents. Following PCI, he suffered acute profound hypotension necessitating intravenous fluids and vasopressor support with epinephrine. Emergency transthoracic echocardiogram did not reveal any pericardial effusion, and showed normal left ventricle and right ventricle systolic function. The Impella device was removed and selective left common iliac angiogram from the right femoral access revealed a vascular injury site with shift of the bladder to the right indicative of retroperitoneal hematoma. A digital subtraction angiogram revealed extravasation of blood at the vascular injury site. An 8.0 × 59 mm iCAST covered stent was deployed to the left external iliac artery with successful sealing of the perforation. The Impella device site was closed with two Perclose devices. The patient required 4 units of packed red blood cell transfusion. His hospital course was complicated by transient acute kidney injury, with return of his renal function to baseline at discharge 10 days later. This case underscores the importance of prompt recognition and treatment of vascular complications associated with interventional procedures, and highlights some of the risk predictors of such complications, which should be anticipated and planned for prior to intervention.

Coronary Perforation of Distal Diagonal Branch Followed by Prolonged Recurrent Cardiac Tamponade Finally Resolved with Pericardiotomy - the Potential Risk of Hydrophilic Guide-Wires

Purpose:

Coronary artery perforation (CAP) is a complication of percutaneous coronary interventions (PCIs). Hydrophilic guide-wires have been shown to increase the probability of CAP. Depending on the size of perforations we adopt different treatments.

Case:

We present the case of a 73-year old male with coronary artery disease and severe aortic valve stenosis. The patient was in the process of qualifying for a transcatheter aortic valve implantation. Unfortunately, CAP of the first diagonal branch of the LAD occurred during PCI. Initially, abrupt bleeding to the pericardial sac was primarily restrained. However, in the following days, pericardial bleeding became silent, prolonged and finally resulted in surgical pericardiotomy and surgical aortic valve replacement.

Conclusion:

This case depicts that in some cases, more aggressive endovascular treatment of CAP during the acute phase could decrease the probability of future radical surgical treatment. Although, in other cases, avoiding radical endovascular treatment of CAP and secondary necrosis along the distribution of the artery culminates in a higher risk for conversion to a surgical cardiac procedure. Accurate primary assessment of CAP seriousness and careful observation after PCI could improve results and lead to avoiding severe complications.

An in vivo pilot study of a microporous thin film nitinol-covered stent to assess the effect of porosity and pore geometry on device interaction with the vessel wall

Sputter-deposited thin film nitinol constructs with various micropatterns were fabricated to evaluate their effect on the vessel wall in vivo when used as a covering for commercially available stents. Thin film nitinol constructs were used to cover stents and deployed in non-diseased swine arteries. Swine were sacrificed after approximately four weeks and the thin film nitinol-covered stents were removed for histopathologic evaluation. Histopathology revealed differences in neointimal thickness that correlated with the thin film nitinol micropattern. Devices covered with thin film nitinol with a lateral × vertical length = 20 × 40 µm diamond pattern had minimal neointimal growth with well-organized cell architecture and little evidence of ongoing inflammation. Devices covered with thin film nitinol with smaller fenestrations exhibited a relatively thick neointimal layer with inflammation and larger fenestrations showed migration of inflammatory and smooth muscle cells through the micro fenestrations. This “proof-of-concept” study suggests that there may be an ideal thin film nitinol porosity and pore geometry to encourage endothelialization and incorporation of the device into the vessel wall. Future work will be needed to determine the optimal pore size and geometry to minimize neointimal proliferation and in-stent stenosis.

Coronary bypass graft perforation during percutaneous intervention

INTRODUCTION

Coronary artery bypass grafts are prone to accelerated atherosclerosis and as such graft stenosis is frequently encountered in clinical practice. Complications specific to graft- PCI include no-reflow, distal embolization, stent restenosis and thrombosis. Graft perforation during PCI is a rare coomplication of the procedure. Published literature on the predictors of perforation and management strategy remains limited to anecdotal cases.

METHOD

In this review we collected data on all cases of graft perforations reported in PubMed/Medline from 1987 to 2015.

RESULT

37 cases of graft perforation were reported. High risk grafts for perforations included, old grafts (14±7.8years) with more than 80% luminal stenosis. Perforations were noted after use of different cardiac devices and included stent placement (30%, N=11), balloon angioplasty (36%, N=14), post-dilation with non complaint balloon (16%, N=6), guide wire perforation (1 case), post IVUS imaging (1 case) and one case after use of thrombus extraction device. Average stent diameter of 3.7±0.7 mm, average balloon pressure of 15.5±5 atm and 3 or more balloon inflations commonly resulted in graft perforation. 78% of cases reported class III perforation. Covered stent implantation was strongly associated with controlling acute bleed after graft perforation than prolonged balloon inflation (p=0.0001). Majority of cases reported using covered stents (81%). Average stent diameter of 3.9±0.7mm, average stent length of 18.5±6mm and the average deployment pressure of 14±2atm were reported to be effective in controlling the bleed. 95% of the patients did well post procedure and with prolonged hospitalization (8±4days). 24% of cases reported cardiac tamponade causing hemodynamic compromise including 2 peri-procedural deaths.

CONCLUSION

Graft perforation can be effectively treated with covered stent grafts with good immediate results, short term outcome and acceptable peri-procedural risks.

Next generation covered stents made from nanocomposite materials: A complete assessment of uniformity, integrity and biomechanical properties

Covered stents are stents wrapped with a thin polymeric membrane, and are typically used to treat vessel aneurysms and seal perforated arteries. Current covered stents suffer from restenosis due to limitations in material and fabrication methods which leaves metallic struts directly exposed to blood. We have developed a biocompatible and haemocompatible nanocomposite polymer, polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU). We devised a novel combination of ultrasonic spray atomisation system and dip-coating process to produce small calibre covered stents with metal struts fully embedded within the membrane, which also yields greater coating uniformity. Stent-polymer bonding was enhanced via silanisation and coating of reactive pre-polymer. Platelet studies supported the non-thrombogenicity of POSS-PCU. Biomechanical performances including diametrical compliance, bending strength, radial strength and recoil were evaluated and optimised. This proof-of-principle manufacturing technique could lead to the development of next-generation small calibre adult and paediatric covered stents. These stents are currently undergoing preclinical trial. From the Clinical Editor: The use of stents to treat vascular diseases is now the standard of care in the clinical setting. Nonetheless, a major problem of the current stents is the risk of restenosis and thrombosis. The authors developed a nanocomposite material using polyhedral oligomeric silsesquioxane and poly(carbonate-urea) urethane (POSS-PCU) and incorporated into metallic stents. Preliminary data have already shown promising results. It is envisaged that this would further lead to better stent technology in the future.

Ruptured saphenous vein graft pseudoaneurysm successfully treated with covered stents

Saphenous vein graft (SVG) pseudoaneurysms are rare complications following coronary bypass graft surgery. A 46-year-old man presented with streptococcal infectious endocarditis and needed sequential operations for aortic root reconstruction. Shortly after the surgeries, a composite SVG on the right coronary artery developed a ruptured pseudoaneurysm, which was successfully treated using covered stents.

Elastin-like recombinamer-covered stents: Towards a fully biocompatible and non-thrombogenic device for cardiovascular diseases

We explored the use of recently developed gels obtained by the catalyst free click reaction of elastin-like recombinamers (ELRs) to fabricate a new class of covered stents. The approach consists in embedding bare metal stents in the ELR gels by injection molding, followed by endothelialization under dynamic pressure and flow conditions in a bioreactor. The mechanical properties of the gels could be easily tuned by choosing the adequate concentration of the ELR components and their biofunctionality could be tailored by inserting specific sequences (RGD and REDV). The ELR-covered stents exhibited mechanical stability under high flow conditions and could undergo crimping and deployment without damage. The presence of RGD in the ELR used to cover the stent supported full endothelialization in less than 2weeks in vitro. Minimal platelet adhesion and fibrin adsorption were detected after exposure to blood, as shown by immunostaining and scanning electron microscopy. These results prove the potential of this approach towards a new and more effective generation of covered stents which exclude the atherosclerotic plaque from the blood stream and have high biocompatibility, physiological hemocompatibility and reduced response of the immune system.

Endoluminal occlusion devices: technology update

Endoluminal occlusion has been performed since the early beginning of interventional radiology. Over recent decades, major technological advances have improved the techniques used and different devices have been developed for changing conditions. Most of these occlusion devices have been implemented in the vascular territory. Early embolization materials included glass particles, hot contrast, paraffin, fibrin, and tissue fragments such as muscle fibers and blood clots; today, occlusion materials include metallic devices, particles, and liquid materials, which can be indicated for proximal or distal occlusion, high-flow and low-flow situations, and in large-caliber and small-caliber vessels, based on need. Technological progress has led to a decreased size of delivery catheters, and an increase in safety due to release systems that permit the withdrawing and replacement of embolization material. Furthermore, bioactive embolization materials have been developed to increase the efficacy of embolization or the biological effect of medication. Finally, materials have been modified for changing indications. Intravascular stents were initially developed to keep an artery open; however, by adding a covering membrane, these stents can be used to occlude the wall of a vessel or other endoluminal structures. This article gives an overview of the devices most utilized for occlusion of endoluminal structures, as well as their major purpose in the endovascular territory.

Outcomes of covered versus bare-metal balloon-expandable stents for aortoiliac occlusive disease

OBJECTIVE

Randomized trials and retrospective data suggest that covered balloon-expandable (CBE) stents have better short-term patency compared with balloon-expandable bare-metal stents (BMSs) in the treatment of iliac artery disease. This study evaluated midterm outcomes of BMSs vs CBE stents placed in the common iliac artery (CIA) for aortoiliac occlusive disease.

METHODS

All endovascular interventions for symptomatic peripheral arterial occlusive disease performed at a single institution from 2006 to 2012 were reviewed. Patients undergoing stent placement in the CIA segment were included in the analysis. Demographic data, TransAtlantic Inter-Society Consensus (TASC) classification, stent type, patency, and limb reinterventions were compared.

RESULTS

For treatment of de novo distal aorta or CIA stenosis, 254 procedures were performed in 162 patients. BMSs were used in 190 arteries; CBE stents were used in 64 arteries. There was no difference in age, gender, or TASC classification between the two groups. Mean follow-up was 22 ± 16 months. Primary patency, assisted patency, and secondary patency were significantly better in the BMS group. CIAs treated with covered stents were more likely at 1 year or longer to require repeated intervention (hazard ratio, 2.5; 95% confidence interval, 1.2-5.3; P = .009). TASC classification did not predict need for reintervention in either group. Multivariate analysis revealed dual antiplatelet therapy to be the only other factor to affect patency during long-term follow-up.

CONCLUSIONS

In this study, BMSs had significantly better patency compared with CBE stents for treatment of aortoiliac occlusive disease. A randomized trial comparing patency as well as restenosis rates with long-term follow-up is needed to determine if there is any benefit from use of covered stents in the aortoiliac segment.

Successful management of coronary artery rupture with stent-graft: a case report

Perforation of coronary arteries is a relatively rare yet life-threatening complication of percutaneus coronary interventions and is encountered in approximately 0.5% of these procedures. According to the type of coronary perforation, various methods of correction are employed, ranging from conservative approach to emergency cardiac surgery. Coronary stent-grafts are composed of two metal stents and a polytetrafluoroethylene layer between them. Advent of such stents enabled efficient endovascular repair of coronary artery perforation. We present a case of coronary artery perforation which had occurred during stent implantation for the treatment of a bridged segment in the distal portion of the left anterior descending artery. This perforation was successfully managed by implanting a stent-graft.

Management and outcomes of coronary artery perforations during percutaneous treatment of acute coronary syndromes

BACKGROUND

Coronary artery perforation (CAP) is an infrequent and life-threatening complication of percutaneous coronary intervention (PCI), requiring prompt intervention. There is insufficient data about the prognosis and management of CAP in patients with acute coronary syndrome (ACS). The aim of this study was to investigate the management of CAP in patients with ACS.

METHODS

The results of 25 patients with CAP were retrospectively analyzed.

RESULTS

Of the 25 patients, 14 patients (56%) had ACS. According to the Ellis classification, the grade of perforation was type-I in 8 (32%) patients, type-II in 6 (24%) patients and type-III in 11 (44%) patients. Prolonged balloon inflation was performed to 20 (80%) cases of CAP. It successfully sealed the perforation in three cases of type-I, five cases of type-II CAP and in seven cases of type-III CAP. Seven patients underwent covered stent implantation. Emergent CABG was required in two patients with type-III CAP. In-hospital mortality was not observed in the patients.

CONCLUSION

The outcomes of CAP in patients with ACS were similar to patients with stable coronary disease. The continuation of anti-platelet agents after the successful management of CAP may be encouraged in these patients.

DISCOVER: Dutch Iliac Stent trial: COVERed balloon-expandable versus uncovered balloon-expandable stents in the common iliac artery: study protocol for a randomized controlled trial

BACKGROUND

Iliac artery atherosclerotic disease may cause intermittent claudication and critical limb ischemia. It can lead to serious complications such as infection, amputation and even death. Revascularization relieves symptoms and prevents these complications. Historically, open surgical repair, in the form of endarterectomy or bypass, was used. Over the last decade, endovascular repair has become the first choice of treatment for iliac arterial occlusive disease. No definitive consensus has emerged about the best endovascular strategy and which type of stent, if any, to use. However, in more advanced disease, that is, long or multiple stenoses or occlusions, literature is most supportive of primary stenting with a balloon-expandable stent in the common iliac artery (Jongkind V et al., J Vasc Surg 52:1376-1383,2010). Recently, a PTFE-covered balloon-expandable stent (Advanta V12, Atrium Medical Inc., Hudson, NH, USA) has been introduced for the iliac artery. Covering stents with PTFE has been shown to lead to less neo-intimal hyperplasia and this might lower restenosis rates (Dolmatch B et al. J Vasc Interv Radiol 18:527-534,2007, Marin ML et al. J Vasc Interv Radiol 7:651-656,1996, Virmani R et al. J Vasc Interv Radiol 10:445-456,1999). However, only one RCT, of mediocre quality has been published on this stent in the common iliac artery (Mwipatayi BP et al. J Vasc Surg 54:1561-1570,2011, Bekken JA et al. J Vasc Surg 55:1545-1546,2012). Our hypothesis is that covered balloon-expandable stents lead to better results when compared to uncovered balloon-expandable stents.

METHODS/DESIGN

This is a prospective, randomized, controlled, double-blind, multi-center trial. The study population consists of human volunteers aged over 18 years, with symptomatic advanced atherosclerotic disease of the common iliac artery, defined as stenoses longer than 3 cm and occlusions. A total of 174 patients will be included. The control group will undergo endovascular dilatation or revascularization of the common iliac artery, followed by placement of one or more uncovered balloon-expandable stents. The study group will undergo the same treatment, however one or more PTFE-covered balloon-expandable stents will be placed. When necessary, the aorta, external iliac artery, common femoral artery, superficial femoral artery and deep femoral artery will be treated, using the standard treatment. The primary endpoint is absence of binary restenosis rate. Secondary endpoints are reocclusion rate, target-lesion revascularization rate, clinical success, procedural success, hemodynamic success, major amputation rate, complication rate and mortality rate. Main study parameters are age, gender, relevant co-morbidity, and several patient, disease and procedure-related parameters.

TRIAL REGISTRATION

Dutch Trial Register, NTR3381.

Coronary perforation and covered stents: an update and review

Coronary perforation is a rare complication of percutaneous coronary intervention. We present two different types of coronary intervention, but both ending with coronary perforation. However, these perforations were tackled successfully by covered stents. This article reviews the incidence, causes, presentation, and management of coronary perforation in the present era of aggressive interventional cardiology. Coronary perforations are classified as type I (extraluminal crater), II (myocardial or pericardial blushing), and III (contrast streaming or cavity spilling). Types I and II coronary perforations are caused by stiff or hydrophilic guidewires. Type I has a benign prognosis, whereas type II coronary perforations have the potential to progress to tamponade. Type III coronary perforations are caused by balloons, stents, or other intracoronary devices and commonly lead to cardiac tamponade necessitating pericardial drainage. However, type III perforations can be managed with covered stents without need for surgical intervention.

Covered stents for coronary perforations: is there enough evidence?

Covered stents have shown discouraging results when tested on saphenous vein grafts and when attempting to prevent restenosis on native coronary arteries. However, covered stents seem to be a unique tool when a coronary artery perforation complicates percutaneous coronary intervention. Because a randomized clinical trial is not likely to be conducted in this bail-out scenario, the data supporting its use come from case reports and small-size retrospective studies. This review summarizes the available evidence supporting the use of covered stents to treat coronary perforations.

Evaluation of a second-generation self-expanding variable-porosity flow diverter in a rabbit elastase aneurysm model

BACKGROUND AND PURPOSE

The self-expanding V-POD is a second-generation flow-diverting device with a low-porosity PTFE patch on a self-expanding microstent. The authors evaluated this device for the treatment of elastase-induced aneurysms in rabbits.

MATERIALS AND METHODS

Three V-POD types (A, circumferential patch closed-cell stent [n = 9]; B, asymmetric patch closed-cell stent [n = 7]; and C, asymmetric patch open-cell stent [n = 4]) were evaluated by using angiography, conebeam micro-CT, histology, and SEM. Aneurysm flow modifications were expressed in terms of immediate poststent/prestent ratios of maximum CA volume entering the aneurysm dome tracked on procedural angiograms. Flow modifications were correlated with 4 weeks' follow-up angiographic, micro-CT, histologic, and SEM results.

RESULTS

Mechanical stent-deployment difficulties in 4 aneurysms (1 type A; 3 type B) led to suboptimal results and exclusion from analysis. Of the remaining 16 aneurysms, 4-week post-treatment angiograms showed no aneurysm filling in 10 (63%), 3 (∼19%) had no filling with a small remnant neck, and 3 (∼19%) had <0.25 filling. Successfully treated aneurysms (n = 16) demonstrated an immediate poststent/prestent CA maximum volume ratio of 0.13 ± 0.18% (0.0%-0.5%). Favorable contrast-flow modification on immediate angiography after deployment correlated significantly with aneurysm occlusion on follow-up angiography, micro-CT, and histology. The occlusion percentage derived from micro-CT was 96 ± 6.8%. Histology indicated advanced healing (grade ≥3) in the aneurysm dome in 13 of 16 cases. SEM revealed 15 of 16 stents in an advanced state of endothelialization.

CONCLUSIONS

This study showed the feasibility and effectiveness of V-POD for aneurysm healing in a rabbit elastase model.

Proline metabolism and microenvironmental stress

Proline, the only proteinogenic secondary amino acid, is metabolized by its own family of enzymes responding to metabolic stress and participating in metabolic signaling. Collagen in extracellular matrix, connective tissue, and bone is an abundant reservoir for proline. Matrix metalloproteinases degrading collagen are activated during stress to make proline available, and proline oxidase, the first enzyme in proline degradation, is induced by p53, peroxisome proliferator-activated receptor gamma (PPARgamma) and its ligands, and by AMP-activated protein kinase downregulating mTOR. Metabolism of proline generates electrons to produce ROS and initiates a variety of downstream effects, including blockade of the cell cycle, autophagy, and apoptosis. The electrons can also enter the electron transport chain to produce adenosine triphosphate for survival under nutrient stress. Pyrroline-5-carboxylate, the product of proline oxidation, is recycled back to proline with redox transfers or is sequentially converted to glutamate and alpha-ketoglutarate. The latter augments the prolyl hydroxylation of hypoxia-inducible factor-1alpha and its proteasomal degradation. These effects of proline oxidase, as well as its decreased levels in tumors, support its role as a tumor suppressor. The mechanism for its decrease is mediated by a specific microRNA. The metabolic signaling by proline oxidase between oxidized low-density lipoproteins and autophagy provides a functional link between obesity and increased cancer risk.