Information on the most widely used ASTM standards within the materials testing industry
ISO 25539‑2:2020 Cardiovascular implants - Endovascular devices - Part 2: Vascular stents
ISO 25539-2 specifies mechanical performance tests as core bench evaluations for stent systems (stent + delivery system + integrated balloon), plus supplementary tests for materials, biology, clinical, sterilization, and packaging. Include the Axial, bending, torsional, Pulsatile Durability, Radial Loading test etc., Below is the details mechanical testing introduction, UnitedTest offer most of the testing equipment required, contact with our engineer today for more details at export@unitedtest.com.
Mechanical tests verify short-term operability (delivery, deployment, withdrawal) and long-term structural stability (fatigue, patency) of vascular stents.
All tests are performed at 37±2 °C (physiological temperature) with sterilized, clinically conditioned samples.
1, Fatigue & Durability Tests
Evaluate long-term structural integrity under cyclic physiological loads (10-year design life simulation).
| Item | Details |
|---|---|
| Test Types | Radial loading, axial, bending, torsional, compressive fatigue & durability |
| Test Equipment | Cyclic fatigue tester, load/displacement sensor, cycle counter, 37 °C PBS fluid bath, mock vessels (silicone), microscope/SEM/radiography |
| Test Sample | Full stent or justified segments; worst-case failure-risk size; pre-conditioned (tracked through tortuous anatomy, deployed); overlapping stents/stent+endovascular prosthesis |
| Test Procedure | 1.Sterilize and condition samples (simulate clinical delivery/deployment) 2.Mount stent in mock vessel/test fixture (anti-migration) 3.Apply physiological cyclic load: radial (pulsatile pressure), axial (stretch/shorten), bending (radius of curvature), torsion (angle/length), compression (perpendicular to axis) 4.Cyclic loading: ≥380 million cycles (pulsatile, 10-year life); non-pulsatile cycles justified 5.Periodic inspection (deformation, migration); post-test inspection (fracture, wear, delamination) with SEM for fracture analysis |
| Features | Multi-directional load simulation; accelerated cyclic testing; not applicable to absorbable stents |
| Importance | Prevent in-vivo fracture, embolism, or occlusion; validate long-term mechanical reliability |
| Application | All vascular stents, especially stents near joints/moving anatomy (superficial femoral, venous stents) |
2. Stent System Mechanical Tests
Evaluate delivery system-stent mechanical interaction (delivery, deployment, withdrawal safety).
| Item | Details |
|---|---|
| Test Items | Dislodgement force (pre-mounted balloon-expandable), deployment force (self-expandable), tensile/torsional bond strength, profile effect/flaring |
| Test Equipment | Universal mechanical tester, torque tester, tortuous anatomical model, diameter measuring device. |
| Test Sample | Sterilized stent systems (stent + delivery system) |
| Test Procedure | Dislodgement force: Fix stent → pull delivery system → record peak proximal/distal force Deployment force: Simulate anatomy → measure force for all deployment steps Bond strength: Tension/torsion delivery system joints → test failure load/torque Profile effect: Track through tortuous path → measure stent-balloon outer diameter difference. |
| Features | Focus on delivery system performance; simulate clinical operating forces |
| Importance | Prevent intra-procedural dislodgement, bond failure, or vessel injury |
| Application | All stent delivery systems |
3. Integrated Balloon Mechanical Tests
Validate performance of balloons integrated with stent systems.
| Item | Details |
|---|---|
| Test Items | Balloon deflation time, rated burst pressure (RBP), balloon fatigue, dogboning |
| Test Equipment | 37 °C water bath, inflation device, pressure gauge, timer, diameter measuring tool |
| Test Sample | Stent system-integrated balloons |
| Test Procedure | Deflation time: Inflate → deflate → record time to deflated stat RBP: Incremental inflation → measure burst pressure → calculate RBP (99.9% reliability, 95% confidence) Fatigue: Cyclic inflation to RBP → test tolerated cycles Dogboning: Inflate to max pressure → measure balloon diameter beyond stent ends |
| Features | Specific to stent-integrated balloons (not standard angioplasty balloons) |
| Importance | Prevent balloon rupture, slow deflation, or vessel overstretch injury |
| Application | Balloon-expandable stent systems |
4. Patency-Related Mechanical Tests
Verify lumen patency (resistance to collapse, kink, deformation).
| Item | Details |
|---|---|
| Test Items | Perpendicular load compression resistance (self-expandable), perpendicular/radial crush resistance (balloon-expandable), radial force (self-expandable), kink resistance, stent-free/outer surface area |
| Test Equipment | Universal mechanical tester (flat plate/cylindrical compression fixtures), radial force tester (iris tester), kink test gauge/bending model, laser micrometer, CAD software (surface area) |
| Test Sample | Deployed stents (full size); overlapping stents (if clinically applicable) |
| Test Procedure | Compression/crush: Apply perpendicular/radial load → measure force at specified displacement/permanent deformation → check shape recovery Radial force: Constrict/expand self-expandable stent → record outward force at target diameters Kink resistance: Bend stent → measure minimum kink-free radius; check recovery (self-expandable) Surface area: Calculate free surface area (%) and outer contact area (mm²) via CAD |
| Features | Differentiate self-expandable/balloon-expandable and implant sites; direct patency correlation |
| Importance | Maintain lumen patency; avoid collapse, kink, or branch vessel obstruction |
| Application | Venous stents, peripheral artery stents, stents in non-aortic/non-coronary/non-renal locations |
Related products and device
Related Standard
ISO 25539‑1 applies to endovascular prostheses (stent‑grafts) and their delivery systems. It defines a complete set of mechanical tests covering fatigue, fixation, patency, strength, and dimensional stability. Mainly test include Axial, bending, torsional, Pulsatile Durability, Radial fatigue.
ASTM F2477 designed to evaluate the long-term fatigue durability and radial cyclic deformation resistance of vascular implants under simulated physiological pulsatile loading conditions. It is crucial for simulating the cyclical stresses these medical devices endure inside human blood vessels.
ASTM F3067 establishes in vitro test frameworks to characterize the radial mechanical performance of balloon-expandable vascular stents and self-expanding vascular stents. It quantifies three key indicators: radial strength and collapse pressure for balloon-expandable stents, and chronic outward force (COF) for self-expanding stents.
ASTM F2606 defines quantitative three-point bending procedures to characterize the bending flexibility and stiffness of balloon-expandable vascular stents and stent systems (pre-deployment and deployed states). It is a critical testing protocol in the biomedical engineering field. Since vascular anatomies are naturally curved and tortuous, a stent must be flexible enough to navigate through the delivery pathway (trackability) and conform to the vessel's curvature once deployed without causing vascular trauma . This standard provides the guidelines to measure these mechanical properties accurately.
ASTM F2942 specifies in vitro test methodologies to evaluate the cyclic durability of vascular stents under non-radial mechanical deformations (axial, bending, and torsion) that occur in vivo due to musculoskeletal motion, breathing, or cardiac activity.
ASTM F2942 specifies in vitro test methodologies to evaluate the cyclic durability of vascular stents under non-radial mechanical deformations (axial, bending, and torsion) that occur in vivo due to musculoskeletal motion, breathing, or cardiac activity. include Axial, bending, torsional, Pulsatile Durability, Radial Loading etc., test.
Based on the ISO/TS 17137 standard the evaluation of mechanical properties is a critical part of the design and safety validation process. Mechanical Evaluation like tension, radial force, Cyclic Fatigue Durability like constant pulsing. Because absorbable implants lose their structural integrity over time through degradation, their mechanical performance must be assessed not just at the time of implantation, but throughout their intended functional lifetime.
ISO 12417-1 specifies requirements for Vascular Device-Drug Combination Products (VDDCPs) (drug-eluting stents, drug-coated balloons, drug-bearing vascular grafts, etc.). It mandates mechanical tests for the device part (DP) (to verify structural/functional integrity) and a suite of drug-related, physicochemical, biological, and clinical tests. Mechanical performance must comply with device-specific standards (ISO 25539-2, ISO 10555-4, ISO 7198) and remain unaffected by the drug-containing part (DCP).
ISO 7198 specifies test and performance requirements for tubular vascular grafts and vascular patches (surgical vascular prostheses). It defines mechanical tests (with full method/equipment/sample details) and other physicochemical, biological, dimensional, preclinical/clinical tests.
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