Why Patencies of Femoropopliteal Bypass Grafts with Distal End-to-End Anastomosis are Comparable with End-to-Side Anastomosis.

Objective: Despite the theoretical favourable hemodynamic advantage of end-to-end anastomosis (ETE), femoropopliteal bypasses with distal ETE and end-to-side anastomosis (ETS) have comparable clinical patencies. We therefore studied the effects of different in vivo anastomotic configurations on hemodynamics in geometrically realistic ETE and ETS in vitro flow models to explain this phenomenon.

Methods: Four ETE and two ETS models (30° and 60°) were constructed from in vivo computed tomography angiography data.

Computational fluid dynamic analysis of the effect of morphologic features on distraction forces in fenestrated stent grafts.

Objective: Secure fixation of endovascular stent grafts is essential for successful endovascular aneurysm repair. Hemodynamic distraction forces are generated by blood pressure and blood flow and act against fixation force to encourage migration that may eventually lead to late stent graft failure. The aim of this in silico study was to determine which morphologic features were associated with greater distraction force.

Closure technique after carotid endarterectomy influences local hemodynamics.

Background: Meta-analysis supports patch angioplasty after carotid endarterectomy (CEA); however, studies indicate considerable variation in practice. The hemodynamic effect of a patch is unclear and this study attempted to elucidate this and guide patch width selection.

Methods: Four groups were selected: healthy volunteers and patients undergoing CEA with primary closure, trimmed patch (5 mm), or 8-mm patch angioplasty.

Fatigue and/or failure phenomena observed in the fabric of stent-grafts explanted after adverse events.

In this study, we aimed to investigate changes to the fabric of Talent stent-grafts following implantation of aortic endografts and to determine the possible causes of fatigue and/or failure of the grafts. Six devices were explanted at reoperation (N=5) and autopsy (N=1). Selected segments were assessed nondestructively by gross observation and destructively by analyzing textile characteristics and chemical properties.

Long-term resistance to fracture and/or corrosion of the nitinol wires of the talent stent-graft: observations from a series of explanted devices.

The biodurability of the Nitinol wires used in stent-grafts retrieved from reoperations and autopsy was analyzed to assess the possible causes of fracture and/or corrosion of the stents. The Nitinol wires of six explanted devices presented a corrosion-free surface after in vivo service. The drawing lines in the control wires were still present, but neither burrs nor flakes were observed.

A purpose-built simulator for percutaneous ultrasound-guided renal biopsy.

Aims: To construct a simple and affordable simulator for ultrasoundguided percutaneous renal biopsy.

Material And Methods: The kidney biopsy phantom was constructed by embedding a porcine kidney in gelatine. Silicon carbide and aluminium oxide were used as scattering particles in order to mimic the ultrasound appearance of human tissues.

French sizing of medical devices is not fit for purpose.

Purpose: The purpose of the study is to quantify the variation in the metric equivalent of French size in a range of medical devices, from various manufacturers, used in interventional radiology.

Methods: The labelling of a range of catheters, introducers, drains, balloons, stents, and endografts was examined. Products were chosen to achieve a broad range of French sizes from several manufacturers.

Absence of tissue ingrowth through the textile fabric in a series of explanted clinic stent-grafts.

Using the retrieved devices from one autopsy and five reoperations, the biocompatibility of explanted Talent stent-grafts was investigated to highlight the capacity of the fabric to act as an effective scaffold to regenerate a blood conduit. The autopsy device was encapsulated both internally and externally, but the capsules did not penetrate through the fabric structure. The reoperation devices showed discrete patches of compact fibrin and irregularly scattered mural thrombi.

Fractured superior mesenteric artery stents after fenestrated endovascular aneurysm repair.

Stent fracture after fenestrated endovascular aneurysm repair is a recognized complication. In this report, we record the occurrence of superior mesenteric artery stent fractures in our series and describe the management of embolized stent fragments during secondary intervention.

A stable and real-time nonlinear elastic approach to simulating guidewire and catheter insertions based on Cosserat rod.

Interventional Radiology procedures (e.g., angioplasty, embolization, stent graft placement) provide minimally invasive therapy to treat a wide range of conditions.

The accuracy of computed tomography central luminal line measurements in quantifying stent graft migration.

Purpose: This study evaluated the accuracy of central luminal line (CLL) measurements in quantifying stent graft migration. The bias of the CLL technique together with observer variability were assessed.

Methods: Stent grafts were deployed in plastic aortic phantoms at fixed locations from two side branches.

Guidewire stiffness: what's in a name?

Purpose: To measure the stiffness of commonly used "stiff" guidewires in terms of their flexural modulus, an engineering parameter related to bending stiffness.

Methods: Eleven different intact stiff guidewires were selected to undergo a 3-point bending test performed using a tensile testing machine. Testing was performed on 3 new and intact specimens of each guidewire at 10 locations along the wire's length, excluding the floppy tip.

Magnitude of the forces acting on target vessel stents as a result of a mismatch between native aortic anatomy and fenestrated stent-grafts.

Purpose: To quantify the compression force acting on target vessel stents as a consequence of the misalignment between the native aortic anatomy and the fenestrated stent-graft owing to measuring errors during the design of the device.

Methods: The material properties of a fenestrated Zenith stent-graft were determined using a standardized tensile testing protocol. Aortic anatomy was modeled using fresh porcine aortas that were subjected to tensile testing.

Guidewire and catheter behavioural simulation.

Guidewire and catheter manipulation is a core skill in endovascular interventional radiology. It is usually acquired in an apprenticeship on patients, but this training is expensive and risky. Simulation offers an efficient alternative for core skills training, though the instrument complex behaviour requires accurate replication.

Simulation of endovascular guidewire behaviour and experimental validation.

Guidewire manipulation is a core skill in endovascular interventional radiology procedures. Simulation-based training offers a valuable alternative for mastering these skills, but requires a faithful replication of complex guidewire behaviour inside the vasculature. This paper presents the integration of real flexural modulus (FM) measurements into our guidewire model that mimics the flexibility of standard guidewires.

Fenestrated stent-graft repair: which stent should be used to secure target vessel fenestrations?

Purpose: To investigate in an in vitro model the ability of different covered and uncovered stents to resist displacement/migration of a fenestrated stent-graft.

Methods: Three different types (2 covered, 1 bare) of commonly used 7-mm balloon-expandable stainless steel stents (Jostent, Advanta V12, and Palmaz Genesis) were investigated in a testing rig consisting of 2 overlapping tubes with 2 sets of 7-mm holes representing bilateral renal artery fenestrations and ostia. The rig was attached to a tensile tester via pneumatic clamps.

Comparison of the fixation strength of standard and fenestrated stent-grafts for endovascular abdominal aortic aneurysm repair.

Purpose: To determine whether fenestrated stent-grafts provide better stability to resist migration than standard non-fenestrated stent-grafts.

Methods: Truncated fenestrated stent-grafts with a single fenestration were deployed in bovine aortic segments with a side branch. Balloon-expandable stents were then delivered into the branches.

EVAR in iliac occlusion.

Purpose: To report the recanalization of an occluded common iliac artery (CIA) to allow endovascular repair of an abdominal aortic aneurysm (AAA) with a bifurcated stent-graft.

Case Report: A 76-year-old man with a 75-mm infrarenal AAA and an occluded right CIA was successfully treated with a Zenith bifurcated stent-graft. The right CIA was recanalized allowing access, delivery, and deployment of the stent-graft.

Poly-L-lactide surfaces subjected to long-term cell cultures: cell proliferation and polymer degradation.

Short term cell cultures are usually grown in contact with biomaterials to assess cytocompatibility. Depending on the rate of material degradation or corrosion, the time of culture can be a key-point in the method which, if too short, may not show any effect of the released material on the cells. A long term culture was therefore carried out with L929 fibroblast cells in contact with PLLA/PDLA samples for up to eight months.

Flow visualization in a model of a bifurcated stent-graft.

Purpose: To use an in vitro flow model to investigate the flow patterns in a bifurcated stent-graft for abdominal aortic aneurysm (AAA) repair.

Methods: Experiments were performed in an in vitro test rig incorporating a simplified non-planar model of an AAA. A two-component bifurcated device consisting of a stent structure and transparent polyurethane "graft" was deployed in the AAA model.

In vivo force during arterial interventional radiology needle puncture procedures.

To adequately simulate the forces generated during interventional radiological (IR) procedures, non intrusive in-vivo methods must be used. Using finger tip mounted, non intrusive capacitance force sensor pads (PPS, Los Angeles, California) we have been able to measure the forces involved in interventional radiology without a change in procedure technique. Data acquired during the process of calibration of the capacitance pads in conjunction with extensive in-vitro needle puncture force measurement using a commercially available tensile tester (Nene Industries, UK) are presented here.

Heterogeneity of tensile strength and matrix metalloproteinase activity in the wall of abdominal aortic aneurysms.

Purpose: To measure the tensile strength of the aneurysm wall and the matrix metalloproteinase (MMP) activity in similar samples of aortic tissue.

Methods: Detailed mechanical testing was conducted on 124 standardized specimens of aneurysm wall harvested from 24 patients undergoing elective aneurysm repair. The intrasac pressure required to cause aneurysm rupture was calculated based upon the Law of Laplace.

Can intrasac pressure monitoring reliably predict failure of endovascular aneurysm repair?

Purpose: To determine if pressure measured at a single location within aneurysm sac thrombus accurately reflects the force applied to the aneurysm wall and the risk of rupture by examining (1) if pressure is distributed uniformly within aneurysm thrombus, (2) the pressure transmission through aneurysm thrombus, and (3) the microstructural basis for pressure transmission.

Methods: Pressure within aneurysm thrombus was measured by direct puncture through the aneurysm wall at 121 sites in 26 patients during open abdominal aortic aneurysm repair. Measurements were taken prior to cross clamping and compared with intrasac pressure measured at 30 sites in 6 patients without aneurysm thrombus (controls).