Stent Testing

Stents are used to unblock clogged arteries and help restore normal blood flow. These stents may be balloon-expandable or self- expanding and may be made from various different materials such as Cobalt chromium (CoCr), Stainless Steel (SS), nitinol (NiTi), bioresorbable (BRS).   A number of methods are used to ensure these devices demonstrate safety, efficacy, and quality, while performing according to their intended use and labeling. We offer comprehensive stent testing services in accordance with ISO standards, ASTM Standards, FDA guidance documents, and the latest peer reviewed research.

ViVitro Labs is a leader in providing standardized as well as customized methods for cutting edge or novel stent designs.

For catheter based delivery systems see additional tests here.

For Stent Graft and Vascular Prosthesis see additional tests here.

 

Stent Testing

Courtesy of Alvimedica

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Acute Particulate Matter Evaluation

An in-line continuous particulate counting system is used to assess the number and sizes of  particles generated during simulated use in real-time inside an anatomical model.

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Conformability to Vessel Wall

Uses the camera to evaluate the ability of the device to adequately contact the vessel wall upon deployment.

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Corrosion Galvanic

Evaluation of corrosion of device with different type of metals.

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Corrosion Potentiodynamic

Corrosion susceptibility of small, metallic, implant medical devices, or components thereof, using cyclic (forward and reverse) potentiodynamic polarization.

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Crossing Profile

A measurement of the maximum diameter over the length of the delivery system, from the proximal end of the mounted stent to the distal tip.

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Crush Resistance - Parallel Plates

The goal of the test is to determine the load required to cause clinically relevant buckling or a deflection equivalent to a diameter reduction of at least 50%, and determine the load and the displacement required to permanently deform or fully collapse the stent. The purpose of the test is to also determine whether the stent recovers from its original geometry after testing.

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Crush Resistance - Pressure Control

The goal of the test is to determine the load or deformation characteristics of the stent while a circumferentially uniform radial load is applied.

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Crush Resistance - Radially Applied Load

Using a constant displacement a radial load is applied to the sample. Force-diameter curves of stent like structures are determined while loading and unloading the sample according to a specified profile.

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Dimensional Attributes

A contactless optical gauging machine is used to measure dimensional attributes of the device.

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Smartscope
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Direct Longitudinal Compression

The purpose of this test is to determine the deformation of the device in response to a compressive force applied longitudinally along axis of the device.

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Dislodgment Force - Stent Securement

Force required to initiate stent displacement from its initial crimped position and to completely dislodge the stent from the delivery system.

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Flexibility / Kink Resistance

Ability of the device to bend in order to accommodate the predetermined clinically relevant radius or angle it will be required to negotiate during access and delivery.

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Local Compression

The purpose of this test is to determine the deformation of the device in response to a localized compressive force perpendicularly applied to the longitudinal axis of the device, and to determine whether the stent recovers its original geometry after testing.

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Percent Solid Area

The reference area is the full cylindrical side surface area for the stent expanded to the labeled diameter (∏ X outside diameter X length at labeled diameter). The solid area is estimated by CAD software. The solid area is determined on unexpanded stents and assumed not to change significantly during expansion. The percent solid area is the ratio of the solid area to the reference area and is reported as a percentage.

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Profile Effect / Flaring

Ensure the distal tip of crimped stent remains in contact with the balloon at all times, while navigating through a tortuous path. The degree of flaring of the stent away from the balloon is measured.

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Radial Fatigue and Pulsatile Durability

Determine the fatigue resistance of a stent using an in-vitro accelerated test.

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Radial Force Measurement

The force-diameter curves of stent like structures are determined while loading and unloading the sample according to a specified profile.

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crush resistance
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Radiopacity

Test specimens are exposed to X-Ray levels necessary for the imaging system and the product or material. Digital analysis method is used to produce the images in accordance with the equipment manufacturer’s instructions. Radiopacity of the device is determined by qualitatively comparing X-ray image(s) of a test sample and a user-defined standard with or without the use of a body mimic.

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Recoil, Foreshortening

The goal of the test is to assess the elastic recoil and foreshortening of balloon expandable stents.

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Scanning Electron Microscopy (SEM) and Optical Inspection

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Simulated Use Pre-conditioning

Before conducting other evaluations, test samples should undergo all the steps a finished device would go through before being implanted in the patient.

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Simulated Use Testing Under Pulsatile Flow

Devices can be subjected to various physiological pulsatile flows and pressures.

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Stent System Compliance

For balloon-expandable stents, a table of inflation pressure versus expanded diameter is developed and included in the labeling. The expanded stent inside diameter at each inflation pressure is the mean of all measurements taken on all stents at that pressure. The inflation pressure is expressed in atmospheres.

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Strut and Bridge Thickness

Strut and bridge thicknesses of the expanded finished stent are measured by direct measurement using a calibrated optical system. Strut and bridge thickness are measured at the stent mid-length and near each end, at two circumferential locations at each axial location. If strut and bridge thicknesses are systematically different by design, they will be measured and reported separately. Direct measurement may require test samples destruction by cutting, or flattening, or both.

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Uniformity of Expansion / Dog Boning Effect

Stent expansion uniformity: Difference between the largest and smallest diameter measurement on a single stent deployed to its labelled diameter.

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ISO 25539-1:2017 Cardiovascular implants — Endovascular devices — Part 1: Endovascular prostheses

ViVitro Labs provides stent testing services such as dimensional verification of the endovascular system, dislodgement force (pre-mounted, balloon-expandable endovascular prosthesis), force to deploy for self-expanding endovascular prostheses,  simulated use, corrosion, fatigue, durability, radial fatigue, radial durability, fixation and seal evaluation, leakage at seal zone, migration resistance, separation force for overlapping endovascular prostheses, patency-related (crush resistance, local compression, and radial force), compression
resistance to perpendicularly applied load, crush resistance with perpendicularly applied load, Crush resistance with radially applied load, radial force.

For catheter based delivery systems see additional tests here. For Stent Graft and Vascular Prosthesis see additional tests here.

ISO 25539-2:2020 Cardiovascular implants —Endovascular devices —Part 2: Vascular stents

ViVitro Labs provides stent testing services such as dogboning, dimensional verification, acute particulate generation, profile effect/flaring, simulated use, tensile bond strength, torsional bond strength, visibility (radiopacity) , corrosion, radial fatigue, radial durability, patency-related (crush resistance, local compression, and radial force), compression resistance to perpendicularly applied load, crush resistance with perpendicularly applied load, Crush resistance with radially applied load, radial force, kink resistance (flexibility) stent-free surface area and stent outer surface area, dimensional verification of test, stent diameter to balloon inflation pressure, stent length, recoil.

For catheter based delivery systems see additional tests here. For Stent Graft and Vascular Prosthesis see additional tests here.

FDA-1545 FDA Guidance: Non-Clinical Engineering Tests and Recommended Labeling for Intravascular Stents and Associated Delivery Systems – Guidance for Industry and FDA Staff

ViVitro Labs provides stent testing services such as stent corrosion resistance (fretting corrosion,  pitting and crevice corrosion potential, galvanic  corrosion), dimensional verification, percent surface area, foreshortening, recoil, stent integrity, radial stiffness, radial strength, radial outward force, fatigue, accelerated durability testing, particulate evaluation, radiopacity, crush resistance , kink resistance, stent securement.

For catheter based delivery systems see additional tests here.

ASTM F2477 – 19  Standard Test Methods for in vitro Pulsatile Durability Testing of Vascular Stents

 

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