The polytetrafluoroethylene-covered stent: a device with multiple potential advantages

Thin-Film Composite Membranes with a Carbon Nanotube Interlayer for Organic Solvent Nanofiltration

Compared to the traditional chemical-crosslinking-based polymer, the porous polytetrafluoroethylene (PTFE) substrate is considered to be an excellent support for the fabrication of thin-film composite (TFC) organic solvent nanofiltration (OSN) membranes. However, the low surface energy and chemical inertness of PTFE membranes presented major challenges for fabricating a polyamide active layer on its surface via interfacial polymerization (IP). In this study, a triple-layered TFC OSN membrane was fabricated via IP, which consisted of a PA top layer on a carbon nanotube (CNT) interlayer covering the macroporous PTFE substrate. The defect-free formation and cross-linking degree of the PA layer can be improved by controlling the CNT deposition amount to achieve a good OSN performance. This new TFC OSN membrane exhibited a high dye rejection (the rejection of Bright blue B > 97%) and a moderate and stable methanol permeated flux of approximately 8.0 L m−2 h−1 bar−1. Moreover, this TFC OSN membrane also exhibited an excellent solvent resistance to various organic solvents and long-term stability during a continuous OSN process.

Outcome after new generation single-layer polytetrafluoroethylene-covered stent implantation for the treatment of coronary artery perforation

AIMS

Coronary artery perforation (CAP) is a rare but severe complication during percutaneous coronary intervention (PCI). Implantation of covered stents (CS) represents a potentially life-saving treatment. Concerns exist regarding limited efficacy and high stent thrombosis (ST) rates related to early generation CS. The aim of this study was to evaluate angiographic and clinical outcomes of patients with CAP treated with a new generation single-layer polytetrafluoroethylene (PTFE)-CS.

METHODS

Between May 2013 and November 2017, we identified a total of 61 patients who underwent implantation of 71 single layer PTFE-CS after CAP. We analyzed angiographic results at follow up (including binary angiographic restenosis [BAR] and late-lumen-loss [LLL]) and clinical outcomes in hospital and at follow up, including target lesion revascularization (TLR), cardiovascular-, and all-cause mortality, myocardial infarction (MI) and stent thrombosis (ST).

RESULTS

Procedural success was achieved in all but two patients (96.7%). Procedure related MI, occurred in 19 cases (31.1%), in hospital death occurred in five cases (8.2%). At follow-up, TLR occurred in 11 cases (18.0%), two patients (3.3%) died from non-cardiovascular cause, there was no case of MI or ST.

CONCLUSIONS

In this retrospective analysis, implantation of a new generation PTFE-CS, for the treatment of CAP showed high technical success rates. Although, periprocedural MI-and in-hospital-death rates remain not inconsiderable, new generation PTFE-CS showed favorable angiographic and clinical efficacy and high safety profile, especially with regard to thrombotic events.

Fabrication of Small Caliber Stent-grafts Using Electrospinning and Balloon Expandable Bare Metal Stents

Stent-grafts are widely used for the treatment of various conditions such as aortic lesions, aneurysms, emboli due to coronary intervention procedures and perforations in vasculature. Such stent-grafts are manufactured by covering a stent with a polymer membrane. An ideal stent-graft should have a biocompatible stent covered by a porous, thromboresistant, and biocompatible polymer membrane which mimics the extracellular matrix thereby promoting injury site healing. The goal of this protocol is to manufacture a small caliber stent-graft by encapsulating a balloon expandable stent within two layers of electrospun polyurethane nanofibers. Electrospinning of polyurethane has been shown to assist in healing by mimicking native extracellular matrix, thereby promoting endothelialization. Electrospinning polyurethane nanofibers on a slowly rotating mandrel enabled us to precisely control the thickness of the nanofibrous membrane, which is essential to achieve a small caliber balloon expandable stent-graft. Mechanical validation by crimping and expansion of the stent-graft has shown that the nanofibrous polyurethane membrane is sufficiently flexible to crimp and expand while staying patent without showing any signs of tearing or delamination. Furthermore, stent-grafts fabricated using the methods described here are capable of being implanted using a coronary intervention procedure using standard size guide catheters.

Therapeutic Endovascular Treatments for Traumatic Vertebral Artery Injuries

OBJECTIVE

Traumatic vertebral artery injuries pose difficulty in early diagnosis and management because of concomitant neurologic dysfunction and limitations in direct surgical access. The purpose of this report is to review endovascular therapy in patients with traumatic vertebral artery injuries for preservation of the parent artery, and to determine the safety and efficacy of such endovascular therapy.

METHODS

Six patients with traumatic vertebral artery lesions were treated using therapeutic endovascular methods. Endovascular therapy was accomplished by stent insertion or coil embolization or both.

RESULTS

Except one patient who underwent coil embolization of a transected vertebral artery, all dissections and pseudoaneurysms were successfully treated by stent placement or stent-assisted coiling with preservation of parent arteries. No additional surgical procedures for vascular lesions were required. There were no delayed neurologic or vascular complications and no lesions recurred during the follow-up period (mean, 36.7 months).

CONCLUSION

The author's experience demonstrates that endovascular therapy using stents and coils is both feasible and safe in the treatment of traumatic vertebral artery injuries. Endovascular therapy selectively eliminated the vascular abnormality while maintaining the normal patency of the cerebral arteries. Long-term follow-up review of these repairs will be necessary to provide a full evaluation of the safety and efficacy of these devices.

Use of polytetrafluoroethylene-covered stent for treatment of coronary artery aneurysm

Coronary artery aneurysm is an uncommon occurrence, yet it is described more often today than in the past as coronary angiography is now routinely used for diagnosis and treatment of ischemic heart disease. However, there is no therapeutic consensus regarding this finding. We present a case of giant coronary artery aneurysm and review the literature on the use of polytetrafluoroethylene-covered stents as a therapeutic option for this condition. Combined antiaggregant therapy is needed after the procedure. Randomized controlled trials of surgery versus covered stents are necessary to define the best treatment for large coronary artery aneurysms.

Procedural efficacy and complications of X-Sizer thrombectomy in de novo and stented lesions

Angiographic thrombus is associated with poorer procedural and clinical outcomes. We report our experience with the X-Sizer thrombectomy device (EndiCOR Medical) from March 2001 to December 2002. Indications for use in 44 patients (33 male; mean age, 60) included myocardial infarction (27), unstable angina (6), periprocedural thrombosis (2), acute (< 24 hr) stent thrombosis (1), and subacute (> 24 hr) stent thrombosis (8). Three cases involved vein grafts. Deployment was successful in 42/44. Difficulty traversing the stent occurred in 5/9 cases of in-stent thrombosis. Median TIMI flow increased from 1 to 2 (P = 0.01) postthrombectomy. Median final TIMI flow was 3. Complications included dissection (1), perforation, device jam on stent (1), disruption of a covered stent (1), distal macro-embolization (4), and transient no-reflow (5). The X-Sizer thrombectomy device improves TIMI flow but does not always prevent distal embolization. Care is needed when treating in-stent thrombosis.

Damage to a covered stent by a thrombectomy device

A 75-year-old with a history of coronary bypass grafting was found to have significant stenoses in a vein graft to the right coronary artery. Symbiot stents, with a polytetrafluoroethylene covering, were used to treat areas in the proximal and middle sections of the graft. The following day, she developed symptoms and signs consistent with an acute inferior infarction. The graft was found to be thrombosed. Thrombectomy was performed using an X-Sizer device, consisting of a helical cutter connected to a vacuum source. This resulted in damage to the stent lining, which led to jamming of the device and subsequent removal of a piece of the stent covering. Treatment was by way of deployment of a long stent within the damaged stent. Recovery was unremarkable. Caution or avoidance of this device appears warranted in the setting of covered stent procedures.