The following tests meet the requirements as stated in ISO 25539-1 "Cardiovascular implants-Endovascular devices-Part 1; Endovascular prostheses" and ISO 7198 "Cardiovascular implants - Tubular vascular prostheses" mechanical strength determination.
Determination of circumferential tensile strength:
The sample in its tubular form is placed on two rounded pins. It is then stretched at a uniform rate until the yield and/or break point is reached.
Determination of longitudinal tensile strength:
The sample in its tubular form is placed with its ends in suitable jaws. It is then stretched at a uniform rate until the yield and/or break point is reached.
Determination of kink radius:
The test objective is to determine the radius of curvature required to begin "kinking" the vascular prosthesis. Samples are placed in a radius template that does not cause kinking or narrowing. The template radius is decreased until slight narrowing or kinking of the prosthesis is measured.
Determination of dynamic compliance:
The test objective is to determine the dynamic compliance of a vascular prosthesis when subjected to mechanical fatigue replicating in vivo preclinical conditions. The test is conducted under simulated physiological conditions with saline at 37°C.
The objective of this test is to determine the force required to create permanent radial deformation in the endovascular prosthesis as measured perpendicular to the longitudinal axis. The sample is placed between two test fixtures and compressed continuously or incrementally until plastic deformation occurs.
Local Compression:Migration Resistance:
The objective of this test is to determine the deformation of a device in response to a localized compressive force, applied perpendicularly to the longitudinal axis of the sample. The test is designed to simulate the physiological geometry of the clinical application. The samples are continuously or incrementally compressed until elastic response no longer occurs.
The objective of this test is to evaluate the ability of a sample to remain stationary (resist migration) under simulated clinical use conditions. The samples are deployed into a mock artery with minimal overlap and then gently pulled out of the artery while measuring the resistance force.
Pull Test for Modular Components:Radial Force:
The objective of this test is to determine the force required to separate the modular components of a sample. The samples are deployed into a mock artery and the ends of the modular assembly are attached to grips. The grips are pulled apart at a constant rate of separation while measuring the force required to separate the components.
The objective of this test is to determine the force exerted by a self-expanding stent, as a function of the stent diameter under the conditions of expansion and compression. The samples are deployed within the testing fixture iris until the initial diameter is less than or equal to the minimum vessel diameter indicated in the IFU. A test engineer will record the force while the stent is expanded to the maximum indicated vessel diameter. Then, the engineer will record the force while the stent is compressed to the minimum nominal indicated vessel diameter. See our radial force testing page for additional details.
Strength of Stent/attachment System to Graft:
The objective of this test is to determine the strength of the fixation or bond between the graft material and the stent/attachment system. The graft material and stent/attachment system are mounted on an appropriate tester and a tensile load is applied to the bond or attachment point to simulate in vivo conditions.
For the tensile and compressive tests, MDT uses ElectroForce® 3000 Series Test Instruments, which operate uisng a linear motor. For compliance testing, MDT uses ElectroForce 9100 Series Stent Testers which operate on the principle of fluid displacement. Electrodynamic linear motors on each end of the tester apply a sinusoidal action which forces fluid into and out of mock arteries causing them to expand and contract. Volumetric displacement can either be measured directly from the pump volume change or using a laser micrometer that measures the outside diameter of the arteries at 1200 scans per second.
Tests are conducted in accordance with ANSI/ISO/IEC 17025-2005. Schedules and resource needs are determined during project kickoff meetings with MDT engineers and the customer. Services are performed in accordance with standard operating procedures and test protocols specific to the project. Standard tests do not begin without a protocol signed by both the customer and an MDT representative. For feasibility or non-standard tests, MDT will develop a method and protocol with customer input and will review the final process with the customer prior to initiation of the test.
The test equipment software monitors the test parameters such as: load, pressure, displacement, strain, rotation, temperature and volume. MDT sends weekly updates to ensure customers are apprised of the status of their test. Updates include raw data collected for the various tests for the customer’s analysis.
For the strength characterization tests listed MDT offers several inspection methods including:
MDT tests are conducted in accordance with ANSI/ISO/IEC 17025-2005. In compliance with this standard, MDT test reports include comprehensive documentation and summary of the test protocol and results. Any test method deviations, additions or exclusions are documented and reviewed with the customer prior to beginning the test. Information within the report includes the specific test conditions, statements of compliance with test protocol, and the estimated measurement uncertainty. The reported results only relate to the items tested. Any opinions and interpretations provided by MDT are clearly marked as such. Any additional information required by customer-specific methods will also be noted. At the conclusion of the test, MDT provides the customer with a Microsoft Windows formatted CD containing copies of all raw data, inspection results, and other information collected during the test (see example test reports).
Please take a few moments to tell us more about your device and test requirements in our short questionnaire, and we will be happy to provide you with a quote.