ASTM F2477-23

Standard Test Methods for <emph type="ital"> in vitro</emph> Pulsatile Durability Testing of Vascular Stents and Endovascular Prostheses

ABSTRACT
This test method covers the procedure for determining the durability of ballon-expandable and self- expanding metal or alloy vascular stents. Tests are performed by exposing specimens to physiologically relevant diametric distention levels using hydrodynamic pulsatile loading. Specimens should have been deployed into a mock or elastically simulated vessel prior to testing. The test methods are valid for determining stent failure due to typical cyclic blood vessel diametric distention and include physiological pressure tests and diameter control tests. These do not address other modes of failure such as dynamic bending, torsion, extension, crushing, or abrasion. Test apparatus include a pressure measurement system, dimensional measurement devices, a cycle counting system, and a temperature control system.
SCOPE
1.1 These test methods cover the determination of the durability of a vascular stent or endoprosthesis by exposing it to diametric deformation by means of hydrodynamic pulsatile loading. This testing occurs on a test sample that has been deployed into a mock (elastically simulated) vessel. The test is conducted for a number of cycles to adequately establish the intended fatigue resistance of the sample.  
1.2 These test methods are applicable to balloon-expandable and self-expanding stents fabricated from metals and metal alloys and endovascular prostheses with metal stents. This standard does not specifically address any attributes unique to coated stents, polymeric stents, or biodegradable stents, although the application of this test method to those products is not precluded.  
1.3 These test methods may be used for assessing stent and endovascular prosthesis durability when exposed to blood vessel cyclic diametric change. These test methods do not address other cyclic loading modes such as bending, torsion, extension, or compression.  
1.4 These test methods are primarily intended for use with physiologically relevant diametric change, however guidance is provided for hyper-physiologic diametric deformation (that is, fatigue to fracture).  
1.5 These test methods do address test conditions for curved mock vessels, however might not address all concerns.  
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2023
• ICS: 11.040.25 - Syringes, needles an catheters
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.30 - Cardiovascular Standards

Relations

• Refers: ASTM F3211-17 - Standard Guide for Fatigue-to-Fracture (FtF) Methodology for Cardiovascular Medical Devices
• Effective Date: 01-Sep-2017
• Refers: ASTM F2514-08 - Standard Guide for Finite Element Analysis (FEA) of Metallic Vascular Stents Subjected to Uniform Radial Loading
• Effective Date: 15-Jul-2008
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM D1193-99e1 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM D1193-99 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999

Overview

ASTM F2477-23: Standard Test Methods for In Vitro Pulsatile Durability Testing of Vascular Stents and Endovascular Prostheses establishes procedures for evaluating the fatigue resistance and durability of balloon-expandable and self-expanding metal or alloy vascular stents. The standard is designed specifically for testing stents and endovascular prostheses in a controlled laboratory setting, simulating the cyclical diametric distention experienced within human blood vessels. It specifies the use of hydrodynamic pulsatile loading within elastically simulated (mock) vessels to mirror physiological conditions and stressors.

This standard is applicable primarily to metallic stents and stent-based endovascular prostheses. While not tailored to coated, polymeric, or biodegradable stents, it doesn’t exclude their evaluation with appropriate justification. ASTM F2477-23 addresses only diametric fatigue under pulsatile conditions and does not cover other forms of loading or potential failure modes such as bending, torsion, compression, or abrasion.

Key Topics

• Scope of Testing

  • Focused on durability and fatigue testing due to cyclic diametric changes mimicking real-life blood pressure variations.
  • Applicable mainly to metallic balloon-expandable and self-expanding stents and endovascular devices.

• Test Methods

  • Physiological Pressure Test: Replicates pulsatile blood pressures (typically 80 to 160 mm Hg) and rates (around 1.2 Hz or 72 beats/min).
  • Diameter Control (Strain Control) Test: Controls and verifies diametric expansion and contraction of deployed stents within the mock vessels.

• Test Apparatus Requirements

  • Pressure measurement and cycle counting systems
  • Dimensional measurement devices (e.g., LVDTs, lasers, high-speed cameras)
  • Calibrated temperature controls, commonly set to 37±2°C to simulate body conditions
  • Mock vessels with relevant compliance to native arteries

• Sample Preparation

  • Uses fully processed, sterilized, implant-quality devices
  • Appropriate sample sizes determined by risk assessment and regulatory needs
  • Deployment in mock vessels reflecting worst-case scenarios

• Test Reporting and Analysis

  • Comprehensive documentation of test parameters, sample information, and any deviations
  • Recording of durability failures including type, location, and cycle count at failure

Applications

• Product Development & Design Verification

  • Assists manufacturers in verifying the fatigue life of vascular stents and endovascular prostheses under simulated physiological loading.
  • Supports selection and optimization of device materials, geometries, and deployment strategies.

• Regulatory Submissions

  • Used to generate evidence for regulatory approval, demonstrating compliance with durability and reliability requirements as set by agencies like the FDA or equivalent international bodies.

• Quality Control & Manufacturing

  • Establishes consistent durability testing protocols for batch release and process validation.
  • Detects manufacturing-induced weaknesses before clinical use.

• Risk Management

  • Contributes data for risk assessments in line with standards such as ISO 14971, identifying potential failure modes under cyclic loading.

Related Standards

For a comprehensive stent durability and verification program, reference the following standards and guides:

• ASTM F2514: Guide for Finite Element Analysis (FEA) of Metallic Vascular Stents
• ASTM F3067: Guide for Radial Loading of Balloon-Expandable and Self-Expanding Vascular Stents
• ASTM F3172: Guide for Device and Sample Size Selection for Endovascular Devices
• ASTM F3211: Guide for Fatigue-to-Fracture Methodology for Cardiovascular Devices
• ISO 7198: Determination of Dynamic Radial Compliance for Tubular Vascular Grafts
• ISO 14971: Medical Devices - Risk Management
• FDA Guidance on Intravascular Stent Non-Clinical Tests

These references help ensure cohesive and internationally recognized test protocols for intravascular device durability and safety.

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Keywords: pulsatile durability testing, vascular stents, endovascular prostheses, ASTM F2477-23, cyclic fatigue, medical device testing, stent durability, hydrodynamic loading, interventional cardiology, quality control, risk management.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2477 − 23
Standard Test Methods for
in vitro Pulsatile Durability Testing of Vascular Stents and
Endovascular Prostheses
This standard is issued under the fixed designation F2477; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.8 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 These test methods cover the determination of the
ization established in the Decision on Principles for the
durability of a vascular stent or endoprosthesis by exposing it
Development of International Standards, Guides and Recom-
to diametric deformation by means of hydrodynamic pulsatile
mendations issued by the World Trade Organization Technical
loading. This testing occurs on a test sample that has been
Barriers to Trade (TBT) Committee.
deployed into a mock (elastically simulated) vessel. The test is
conducted for a number of cycles to adequately establish the
2. Referenced Documents
intended fatigue resistance of the sample.
2.1 ASTM Standards:
1.2 These test methods are applicable to balloon-expandable
D1193 Specification for Reagent Water
and self-expanding stents fabricated from metals and metal
F2514 Guide for Finite Element Analysis (FEA) of Metallic
alloys and endovascular prostheses with metal stents. This
Vascular Stents Subjected to Uniform Radial Loading
standard does not specifically address any attributes unique to
F3067 Guide for Radial Loading of Balloon-Expandable and
coated stents, polymeric stents, or biodegradable stents, al-
Self-Expanding Vascular Stents
though the application of this test method to those products is
F3172 Guide for Design Verification Device Size and
not precluded.
Sample Size Selection for Endovascular Devices
1.3 These test methods may be used for assessing stent and
F3211 Guide for Fatigue-to-Fracture (FtF) Methodology for
endovascular prosthesis durability when exposed to blood
Cardiovascular Medical Devices
vessel cyclic diametric change. These test methods do not 3
2.2 ISO Standards:
address other cyclic loading modes such as bending, torsion,
ISO 7198:2016, A.5.9 Dynamic radial compliance—tubular
extension, or compression.
vascular grafts only
1.4 These test methods are primarily intended for use with ISO 14971 Medical Devices—Application of Risk Manage-
physiologically relevant diametric change, however guidance ment to Medical Devices
is provided for hyper-physiologic diametric deformation (that
3. Terminology
is, fatigue to fracture).
3.1 Definitions of Terms Specific to This Standard:
1.5 These test methods do address test conditions for curved
3.1.1 cardiac cycle, n—defined as one cycle from diastolic
mock vessels, however might not address all concerns.
pressure to systolic pressure and back to diastolic pressure.
1.6 The values stated in SI units are to be regarded as
3.1.2 compliance, n—the change in inner diameter of a
standard. No other units of measurement are included in this
vessel due to cyclic pressure changes. Compliance, if
standard.
calculated, shall be expressed as a percentage of the diameter
1.7 This standard does not purport to address all of the
change per 100 mmHg and defined per ISO 7198, A.5.9, or
safety concerns, if any, associated with its use. It is the
equivalently:
responsibility of the user of this standard to establish appro-
Dp2 2 Dp1 × 10
~ !
priate safety, health, and environmental practices and deter-
%Compliance/100 mm Hg 5 (1)
~Dp1~p2 2 p1!!
mine the applicability of regulatory limitations prior to use.
1 2
These test methods are under the jurisdiction of ASTM Committee F04 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Medical and Surgical Materials and Devices and are the direct responsibility of contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Subcommittee F04.30 on Cardiovascular Standards. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2023. Published February 2023. Originally the ASTM website.
approved in 2006. Last previous edition approved in 2019 as F2477 – 19. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/F2477-23. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2477 − 23
where: due to the cyclic blood pressure changes of the cardiac cycle.
The stent or endoprosthesis shall be deployed into a mock
Dp1 = inner diameter at the pressure of p1,
vessel that can be used to produce a cyclic diameter change of
Dp2 = inner diameter at the pressure of p2,
p1 = lower pressure value (diastolic), in mmHg, and the stent or endoprosthesis. An endoprosthesis being evaluated
p2 = higher pressure value (systolic), in mmHg. for an aneurysm exclusion indication may use a mock vessel
with a simulated aneurysm. Within the aneurysmal sac portion
3.1.3 diametric strain, n—a change in mock vessel or device
of the mock vessel, the endoprosthesis deformation is primarily
diameter divided by the minimum diameter at the measurement
due to cyclic pressure changes relative to the aneurysmal sac
location. This term does not equate to the mechanical strain
rather than the simulated aneurysm dimensional changes. Thus,
seen in the device material. The diametric strain can be
the mock aneurysmal sac compliance is not critical and
identified as:
pressure monitoring of mock vessel might be needed.
~Dp2 2 Dp1!
4.1.1 Pressure Test Method—This test method (provided in
diametric strain 5 (2)
Dp1
Annex A1) requires the use of mock vessels that possess
similar diametric compliance properties to native vessels
that is,
(except within the mock aneurysm, if applicable) at specified
~maxID 2 minID! physiologic pressures (applied externally and/or internally) at
diametric strain 5
minID
the testing frequency. The use of physiologic transmural
pressure (that is, external to internal pressure differential) is
3.1.4 endovascular prosthesis, n—vascular prosthesis (in-
important to ensure the test mimics physiological loading
cluding modular components) which resides partially or com-
conditions. This test method may also be used with external
pletely within a blood vessel, or vascular conduit to form an
physiologic pressures applied to thin non-physiologic mock
internal bypass or shunt between sections of the vascular
vessels.
system, delivered and deployed using a delivery system (from
4.1.2 Diameter Control Test Method—(Sometimes called a
ISO 25539-1). Examples of endovascular prostheses are vas-
strain control test method.) This test method (provided in
cular stent grafts and covered stents.
Annex A2) requires the use of a diameter measurement system
3.1.5 hydrodynamic loading, n—causing a change in the
and mock vessels to ensure that the desired minimum and
diameter of a mock vessel by injecting a volume of fluid into
maximum device diameters, or the equivalent change in device
a confined test volume inside and/or outside the mock vessel.
diameter and mean device diameter, are being achieved at the
3.1.6 mock vessel, n—a simulated vessel typically manufac-
test frequency. For conditions where a direct measurement of
tured from an elastomeric material. The mock vessel is made to
the device is not possible, measurements are typically made
approximate the ID and diametric change of a native vessel at
over the outside diameter (OD) of the mock vessel and a
physiological pressures (see A1.2.2 and A2.4.2) or at non-
relationship is determined and justified for the ratio of the
physiological pressures (see A2.4.4). Mock vessels with a
device OD versus measured mock vessel OD.
simulated aneurysm may be used when evaluating the pulsatile
durability of endovascular prostheses for aneurysmal exclusion
5. Sample Preparation, Device Labeled Size, Sample
indications. Mock vessels with a specified radius of curvature
Configuration, Mock Vessels, and Number of Samples
may also be used.
5.1 Unless otherwise justified, samples selected for testing
3.1.7 native vessel, n—defined as a natural blood vessel.
shall be taken from fully processed implant quality product.
3.1.8 strain control, n—a term to describe control of dia-
Sterilization should be required, unless it can be shown not to
metric change, relative to an initial diameter of the mock
influence the fatigue/durability test results.
vessel, not to be confused with controlling the strain in the
5.2 The number of samples tested for each device geometry
device material.
should be sufficient to support any claims to be made based on
3.1.9 vascular stent, n—a synthetic tubular structure that is
the test results. The number of samples should also be justified
implanted in the native or grafted vasculature and is intended
in the context of the device risk assessment (see Guide F3172
to provide mechanical radial support to enhance vessel patency
and ISO 14971).
over the intended design life of the device. A stent is metallic
5.3 Fatigue/durability shall be evaluated for the worst-case
and not covered by synthetic textile or tissue graft material.
labeled diameter, and a rationale shall be provided stating why
The term stent may also be used to describe the structural
the particular labeled diameter is considered worst case. See
support component(s) of an endovascular prosthesis.
Guide F2514 for guidance in using finite element analysis for
radial loading of stents.
4. Summary of Test Methods
4.1 This document details two test methods that are cur- 5.4 Mock Vessels:
rently used: Pressure Test Method and Diameter Control Test 5.4.1 The choice of diameter of the mock vessel in contact
Method. These test methods cover fatigue/durability testing of with the device is critically important to the effectiveness of
vascular stents and endovascular prostheses that are subjected any durability test. The mean mock vessel diameter in contact
to hydrodynamic loading (internal and/or external pressuriza- with the device over a cardiac cycle should be consistent with
tion) that simulates the radial loading and/or change in diam- the worst-case device diameter for the device being tested, over
eter that the stent or prosthesis is expected to experience in vivo the full test duration.
F2477 − 23
NOTE 1—If implementing fatigue-to-fracture testing, see Appendix X3
the device or the test setup. Rationale for use of a different
for guidance regarding the use of a liner within the mock vessel.
environment shall be provided.
5.4.2 See Annex A1 and Annex A2 for specific require-
7.3 Physiological Blood Pressures—The cyclic pressures in
ments.
the intended blood vessel. Selection of the systolic and
diastolic blood pressures should be based on the patient
5.5 The number of samples, in combination with other tests,
population for which the device is indicated. For example,
animal and clinical tests, analyses such as FEA (Finite Element
suggested systolic and diastolic values for hypertensive arterial
Analysis), and/or comparisons to predicate devices shall be
blood pressures are 160 and 80 mmHg.
sufficient to enable demonstration of an adequate justified
reliability. In these test methods, one device or a pair of
7.4 Physiological Pulse Rate—For the purposes of these test
overlapped devices shall be considered one sample. The
methods, determined to be 1.2 Hz or 72 beats per minute.
reliability justification may reference additional testing and/or
7.5 Vessel Degradation—Mock vessels made of materials
analyses used to establish device durability.
that may degrade with exposure to environmental factors (such
as UV light) shall be protected from such exposure.
6. General Apparatus Requirements
7.6 Device Deployment—The device shall be deployed in
6.1 For test methods requiring precision measurement and
the mock vessel, after tracking through a challenging simulated
control of pressure, dimensions, or cycle counts, verification of
anatomy, in such a manner as to minimize end effects where the
the dynamic performance of these systems at or encompassing
vessel is connected to the test apparatus. Unless testing is to be
the test frequency shall be performed and documented with
conducted with devices overlapped, or as otherwise justified,
justification of the means used.
devices deployed in the same mock vessel shall be at a
sufficient distance to avoid unintended interaction.
6.2 Pressure Measurement System—Pressure transducers
shall be chosen that allow for the accurate evaluation of the
7.7 Test Duration—The test duration shall be justified. The
applied pressures at the frequency pressures are to be mea-
number of cycles associated with an implantation time of ten
sured. See Annex A1 and Annex A2 for method specific
years (for example, for arterial stents at least 380 million
requirements. The pressure measuring system must be cali-
cycles) has been historically used.
brated.
7.8 Test Frequency—See Annex A1 and Annex A2 for
test-specific details.
6.3 Cycle Counting System—The apparatus shall include a
cycle counting system for measuring the number of load cycles
7.9 Device Deformation Verification—Differences in the
applied to the device/mock vessel combination.
contact between the device and the mock vessel (for example,
no contact, too high friction, mock vessel conformability)
6.4 Temperature Control System—The apparatus shall in-
compared to in vivo conditions can result in device deformation
clude a calibrated temperature control and measurement sys-
that is greater or less than intended. Thus, the investigator
tem to provide the testing temperature for devices being tested.
should demonstrate that during the cyclic displacement the
If fluid temperature is measured to indicate device temperature,
device is subjected to the intended deformation (for example,
the relationship between the fluid temperature at the associated
similar deformation of device at 1.2 Hz) at the frequency and
measurement location and the device temperature shall be
pressure used in the durability test. This may be done with a
justified.
high-speed camera; however, a strobe light may also be used
for qualitative verification. The high-speed camera may be
7. General Test Parameters
used to measure the change of the OD of the mock vessel.
7.1 Temperature—The temperature of the device shall be 37
Imaging the device inside of the mock vessel is problematic
6 2 °C. Normally this can be accomplished by controlling the
because of the refraction of light through different media (that
temperature of the fluid adjacent to the device. If other
is, air/silicone/water). See Appendix X2 for additional details
temperatures are to be used, a rationale shall be provided
regarding measuring the deformation of the device inside the
stating why the particular temperature is considered worst case
mock vessel. Also, the proper functionality of a test method
or equivalent. The unit is to be stable over the intended period
used to test a device inside a mock vessel depends on the
of the test and maintained within the established parameters.
device remaining in contact with the ID of the vessel through-
NOTE 2—The presence of a mock vessel liner can induce a temperature out the diametric change of that vessel. This is also true for
differential between the fluid and device. This might require elevation of
endovascular prostheses used to treat occlusive disease. If
the fluid temperature.
evaluating an endovascular prosthesis under aneurysmal
7.2 Solutions—The test solution shall be physiologic pH conditions, the endovascular prosthesis should maintain con-
buffered saline (for example, phosphate buffered saline) or tact with the mock vessel in the seal regions, but not in the
equivalent unless testing in a different environment (such as in aneurysmal sac region. Thus, the investigator shall demonstrate
0.9 % saline, modified simulated body fluid, or Specification that the device or endovascular prosthesis to be tested main-
D1193 Class IV distilled water) can be justified. Biological tains contact with the ID of the mock vessel to be used in the
growth can inhibit post-test evaluation of the device surface durability test throughout a test cycle, except in the aneurysmal
characteristics. Use of a biological growth inhibitor (such as sac region of mock vessel being used to evaluate an endovas-
algaecides or chemical agents) may be used unless such use cular prosthesis under aneurysmal conditions. Device deforma-
would negatively impact the test by unintended degradation of tion verification is not required for every test sample. The
F2477 − 23
number of devices used for the deformation verification should including a justification for considering negative findings as
be adequate and justified. The results of this verification artifacts or discounting their clinical significance.
activity should be used to establish the procedure for ensuring
8.2 Test reports should include:
the intended deformation of the test samples (for example,
8.2.1 Test parameters and acceptance criteria:
utilize test frequency that provides intended deformation). For
8.2.1.1 Test parameters (such as):
example, if it can be shown that the stroke and frequency of the
(1) Mock vessel attributes (for example, ID at pressure,
pulsatile testing apparatus adequately correlates with the in-
compliance).
tended deformation of the device, further deformation verifi-
(2) Device temperature or fluid temperature that has been
cation activities might not be needed. The completion of the
previously correlated to device temperature.
device deformation verification and any justifications shall be
(3) Regions of interest for diametric strain control and
documented in the test report.
associated rationale.
(4) Control parameters (for example, fluid pressure range
7.10 Variation of Loading Along Length as Function of
and variability, desired change in vessel with device diameter).
Frequency—The investigator should be aware of the potential
(5) Minimum level and/or mean of control parameters (for
for pressure variations along the length of a mock vessel that
example, diametric strain, pressure levels) across test samples.
may change in location and magnitude as the test frequency is
8.2.1.2 Acceptance criteria (such as):
changed. Typically, diastolic and systolic pressure levels are
(1) Maximum number and location of failures to define
fairly uniform along the length of the mock vessel at physi-
acceptance.
ologic frequencies, for example 1.2 Hz, but variation in the
(2) Allowable fracture grades (for example, SFA stent
magnitude of either or both of these pressures along the length
fracture grades).
of the mock vessel can increase at hyper-physiologic frequen-
(3) Minimum number of cycles required to define accep-
cies. The test frequency, tester design and configuration, as
tance.
well as the mock vessel compliance, length and diameter, and
8.2.2 Test sample information:
curvature can influence the magnitude of these pressure varia-
8.2.2.1 Number of test samples.
tions along the length of the mock vessel. The pressure
8.2.2.2 Size (diameter, length, or other relevant dimensions)
variations typically cause diametric strain variations along the
of all test samples.
length of the mock vessel. Stiffer mock vessels may be used to
8.2.2.3 Rationale for the number of test samples and sizes
reduce the diametric strain variations. However, in some cases
used.
prior to initiating cyclic fatigue, the investigator might find it
8.2.2.4 Whether the samples are representative of the fin-
difficult to identify a test frequency (for example, during a
ished product.
frequency sweep) that is sufficiently high for a practical test
8.2.2.5 Sterilization parameters and number of sterilization
duration while maintaining acceptable pressure and/or diamet-
cycles applied to the test samples.
ric strain variability along the length of the mock vessel. In
8.2.2.6 Traceability information.
such cases, the investigator may choose to identify region(s) of
8.2.2.7 Pre-conditioning status of samples (for example,
interest on the test sample where test pressures and/or diam-
loaded into a delivery catheter and tracked through a challeng-
eters are to be controlled, while other regions are only
ing anatomy).
monitored. For example, the region(s) of interest would corre-
8.2.3 Materials used:
spond to the location(s) that have been identified through
8.2.3.1 Test equipment.
analysis as having the smallest fatigue safety factor.
8.2.3.2 Mock vessels.
7.11 Evaluation Procedure—A detailed test protocol shall
8.2.3.3 Test fluid/solutions.
be written that describes all procedures unique to the device or
8.2.3.4 Measurement devices.
endovascular prosthesis being evaluated. This protocol shall
8.2.4 Test protocol, including all justifications and ratio-
include any specific failure modes to be identified (for
nales required by these test methods.
example, strut fracture, graft wear, fretting wear) and inspec-
8.2.5 Control values (for example, diametric strain, mean
tions to be performed to identify those failures. Note, a known
ID, alternating and mean pressure, temperature) and associated
test artifact is the artifactual wear that can occur from interac-
tolerances.
tion of the prosthesis with the mock vessel material (for
8.2.6 Protocol deviations.
example, abrasion of graft material between silicone tube and
8.2.7 Mean, standard deviation, minimum, maximum of
device, rate-dependent abrasion properties of polymers) which
measured load condition at each location monitored or con-
tend to be more abrasive, due to higher friction and inability to
trolled for each sample at the specified measurement intervals
mimic in vivo remodeling, than human arteries.
(for example, 50 million, 100 million, 200 million, 380
million). For ease of understanding, the use of a plot to present
8. Test Report
the associated data relative to applicable limits may be used.
8.1 The test report shall include a complete summary of the 8.2.8 Durability reporting:
8.2.8.1 Report any fractures that occur during the test.
materials, methods, and results including any rationale for
deviations from this standard. The effects of any such devia- 8.2.8.2 Fracture information should include: number and
tions on the significance of the test results shall be reported. All locations of all fractures along the length of the device, type of
real, artifact, and anomalous observations shall be reported, fracture such as transverse or spiral, with or without
F2477 − 23
dislocation, and any root cause analysis performed to deter- 8.2.9 Conclusions.
mine the reason for the fracture. Report the number of cycles
9. Precision and Bias
that were applied when the fracture was identified or if
9.1 No information is presented about either the precision or
available, report the number of cycles when the fracture
bias of this test method for measuring durability since the test
occurred.
result is nonquantitative.
8.2.8.3 Report durability observations other than fractures
(for example, fretting wear between overlapped components). 10. Keywords
8.2.8.4 For endovascular prostheses, report as applicable,
10.1 durability test; endovascular cardiology; endovascular
observations of graft material wear, stent to graft attachment
prostheses; fatigue test; interventional cardiology; intravascu-
degradation (for example, suture wear), or other observations lar device test; pressure control; pulsatile fatigue; stent dura-
relevant to the durability of the endovascular prostheses. bility; stent fatigue; stent test; strain control; vascular stent
ANNEXES
(Mandatory Information)
A1. PHYSIOLOGICAL PRESSURE TEST METHOD FOR PULSATILE FATIGUE/DURABILITY TESTING OF VASCULAR
STENTS AND ENDOVASCULAR PROSTHESES
A1.1 Summary of Test Method A1.3.3 Dynamic Compliance Measurement System—The
apparatus should include a diameter measuring system that
A1.1.1 With this technique, when the mock vessel is pres-
allows determination of the ID and dynamic compliance of the
surized from the ID, a volume of fluid is injected into a
mock vessels used in this method and is able to apply
fluid-filled mock vessel that has been manufactured to provide
controlled cyclic physiologic pressures. This system may be
a targeted physiological dynamic diametric compliance. The
the same apparatus as the fatigue/durability testing system. The
injected volume is adjusted so that the measured cyclic
system must operate such that the cyclic diameters and
pressure differential is equivalent to the targeted physiological
pressures can be measured at the test frequency.
pressure differential. The volume of fluid may also be injected
NOTE A1.2—If direct measurement of the ID of the mock vessel is not
into a fixed-volume chamber surrounding the mock vessel to
possible with measurement system used, an empirical method may be
pressurize the OD of the vessel. With external physiologic
used to relate the deployed device outer diameter (OD) with the measured
pressures applied, thin mock vessels may be used in lieu of
mock vessel outer diameter (OD) as found in Appendix X2.
physiological compliant mock vessels.
A1.4 Procedure
A1.2 Significance and Use
A1.4.1 When a physiologic compliant vessel is intended to
A1.2.1 This test method is used to characterize the durabil-
be used, determine the ID and ID dynamic compliance of the
ity of a stent or endovascular prosthesis under simulated
mock vessel at the desired test frequency over the justified
vascular pulsatile conditions, to assess conformance to product
physiologic pressure range. The method (direct OD measure-
specifications and guidance documents, and it may be used to
ment only) outlined in ISO 7198:2016 clause A.5.9 may be
support regulatory submissions, quality control, and manufac-
used, with exception of the tension applied. The mock vessels
turing (for example, process changes).
should be tensioned uniformly (from vessel to vessel) and as
they will be during cyclic testing. Length (pre and post
A1.2.2 This method depends on the use of controlled
tensioned) may be used to set the tension. Tensioning the mock
physiologic pressures and either physiologic compliant vessels
vessel reduces the ID and increases the diametric compliance.
or with externally applied pressures mock vessels that are thin
The pressure transducer(s) shall be placed at the location of
and do not appreciably inhibit intended cyclic diametric
diameter measurements or a location that has been validated at
deformation of the device.
the test frequency. The ID and dynamic compliance may be
NOTE A1.1—With externally applied pressures and thin mock vessels,
determined using one of the options in Appendix X2. These
the cyclic diametric deformation to the device might be greater than the
values are measured to ensure the desired radial loading is
expected in vivo deformation.
applied to the device.
A1.3 Apparatus
NOTE A1.3—When external physiologic pressures applied and thin
mock vessels are used, the compliance of the mock vessel does not need
A1.3.1 See Section 6 for general apparatus requirements.
to be measured. However, the mock vessels must be thin enough to allow
the applied external pressure to be transferred to the device as intended.
A1.3.2 Fatigue/Durability Testing System—The system
must be able to deliver quantifiable pressures to the mock A1.4.2 Deploy the device in the mock vessel following
vessels at the desired test frequency and maintain the device instructions for use. For temperature-dependent devices, de-
temperature as specified (for example, 37 6 2 °C). ployment at 37 6 2 °C might be necessary to ensure a
F2477 − 23
NOTE A1.5—It can be prudent to specify an additional set of tighter
clinically representative deployment. Leave enough length of
tolerances for system adjustment to keep centered within the cyclic
the mock vessel extending beyond each end of the device such
pressure tolerances (that is, warning limits).
that the device will be in the region where the device
deformation is unaffected by any end effects imposed by the A1.4.10 If desired, carry out periodic inspections of the
fatigue/durability test system.
device. If the device is removed from the mock vessel for
inspection, care must be taken to remove and re-deploy it in a
A1.4.3 Inspect the deployed stents in a systematic and
manner that does not destroy the integrity of the test. Periodic
objective manner, using appropriate instruments or techniques,
inspection shall be at the discretion of the device manufacturer.
and record the location and severity of any anomalies. Docu-
ment the inspection locations for correlation to post-test
A1.4.11 When a physiologic compliant vessel is intended to
inspection (see A1.6.2).
be used and the mock vessels have not been previously
A1.4.4 Record proximal and distal locations of each in- validated to have acceptable change in compliance and ID,
stalled device in the mock vessel prior to beginning the test.
periodically re-measure the ID and dynamic compliance of the
mock vessel at the test frequency. The pressure transducer(s)
A1.4.5 Establish the tolerances associated with the cyclic
shall be placed at the location of diameter measurements or a
physiologic pressures. Tolerances may be set for the pressure
location that has been validated at the test frequency. This can
amplitude and pressure mean, or alternatively the maximum
identify any change in loading that can occur. If unacceptable
and minimum pressure. Tolerances do not need to be bilateral.
changes occur, and if possible, without impacting the results of
NOTE A1.4—Tolerance cumulation should be considered when assign-
the test, replace the mock vessel (that is, move the device to a
ing tolerances. For example, when setting tolerances on the minimum and
new mock vessel) preferably without re-deployment of the
maximum pressure, the impact of tolerance cumulation on the pressure
amplitude and pressure mean should be understood. device. If moving the device to a new mock vessel is not
possible, a new device and mock vessel might need to be
A1.4.6 Purge trapped air from the system. As appropriate,
tested.
activate the temperature control system and allow the test
system to equilibrate at 37 6 2 °C (unless otherwise justified).
A1.5 Test Termination
A1.4.7 Start the fatigue/durability test system and adjust the
A1.5.1 Continue to test until the required number of the
frequency to the desired rate and adjust the cyclic pressure
in-tolerance cycles (for example, at least 380 million cycles for
range within tolerance of the justified physiological levels.
a test representative of ten years implantation) has been
Ensure the deformation of the device is as desired at the test
applied.
frequency. If not, an alternative frequency may be needed.
A1.4.8 Zero the counter.
A1.6 Post-Test Inspection
A1.4.9 Periodically monitor and document the cyclic pres-
A1.6.1 When a physiologic compliant vessel is intended to
sures at prospectively specified intervals. Adjust the system as
be used and if the mock vessels have not been previously
necessary to maintain the cyclic pressures within tolerance. If
validated to have acceptable change in compliance and ID over
the cyclic pressures are out-of-tolerance, the cycles between
the duration of the test, re-measure the compliance and the
the last in-tolerance measurement and when the system was
mean inner diameter of the mock vessel at the test frequency
brought back to within tolerance, for any given test sample,
when the test is complete.
shall not be counted toward the number of cycles required for
test termination. A1.6.2 Inspect all devices as required in the protocol.
A2. DIAMETER CONTROL TEST METHOD FOR PULSATILE FATIGUE/DURABILITY TESTING OF VASCULAR STENTS
AND ENDOVASCULAR PROSTHESES
A2.1 Summary of Test Method are commonly used in order to achieve the desired higher
frequency levels. The injected volume is adju
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F2477 − 19 F2477 − 23
Standard Test Methods for
in vitro Pulsatile Durability Testing of Vascular Stents and
Endovascular Prostheses
This standard is issued under the fixed designation F2477; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 These test methods cover the determination of the durability of a vascular stent or endoprosthesis by exposing it to
physiologically relevant diametric distension levels diametric deformation by means of hydrodynamic pulsatile loading. This
testing occurs on a stent test specimensample that has been deployed into a mock (elastically simulated) vessel. The typical
duration of this test is 10 years of equivalent use (at 72 beats per minute), or at least 380 million cycles.test is conducted for a
number of cycles to adequately establish the intended fatigue resistance of the sample.
1.2 These test methods are applicable to balloon-expandable and self-expanding stents fabricated from metals and metal alloys.
It alloys and endovascular prostheses with metal stents. This standard does not specifically address any attributes unique to coated
stents, polymeric stents, or biodegradable stents, although the application of this test method to those products is not precluded.
1.3 These test methods do not include recommendations for endovascular grafts (“stent-grafts”) or other conduit products
commonly used to treat aneurismal disease or peripheral vessel trauma or to provide vascular access, although some information
included herein may be applicable to those devices.
1.3 These test methods are valid for determining stent failure due to typical cyclic blood vessel diametric distension.may be used
for assessing stent and endovascular prosthesis durability when exposed to blood vessel cyclic diametric change. These test
methods do not address other modes of failurecyclic loading modes such as dynamic bending, torsion, extension, crushing, or
abrasion.compression.
1.4 These test methods do not address test conditions for curved mock vessels.are primarily intended for use with physiologically
relevant diametric change, however guidance is provided for hyper-physiologic diametric deformation (that is, fatigue to fracture).
1.5 These test methods do not address test conditions for overlapping stents.curved mock vessels, however might not address all
concerns.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
These test methods are under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and isare the direct responsibility of Subcommittee
F04.30 on Cardiovascular Standards.
Current edition approved June 1, 2019Feb. 1, 2023. Published July 2019February 2023. Originally approved in 2006. Last previous edition approved in 20132019 as
F2477 – 07F2477 – 19.(2013). DOI: 10.1520/F2477-19.10.1520/F2477-23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2477 − 23
1.9 General Caveat—This document contains guidance for testing as is currently carried out in most laboratories. Other testing
techniques may prove to be more effective and are encouraged. Whichever technique is used, it is incumbent upon the tester to
justify the use of the particular technique, instrument, and protocol. This includes the choice of and proper calibration of all
measuring devices. Deviations from any of the suggestions in this document may be appropriate but may require the same level
of comprehensive justification that the techniques described herein will require.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
F2514 Guide for Finite Element Analysis (FEA) of Metallic Vascular Stents Subjected to Uniform Radial Loading
F3067 Guide for Radial Loading of Balloon-Expandable and Self-Expanding Vascular Stents
F3172 Guide for Design Verification Device Size and Sample Size Selection for Endovascular Devices
F3211 Guide for Fatigue-to-Fracture (FtF) Methodology for Cardiovascular Medical Devices
2.2 Other Documents:ISO Standards:
ISO 7198: 1998(e), 8.10,7198:2016, A.5.9 Determination of Dynamic ComplianceDynamic radial compliance—tubular vascular
grafts only
FDA Guidance Document 1545,ISO 14971 Non-Clinical Tests and Recommended Labeling for Intravascular Stents and
Associated Delivery Systems, (issued January 13, 2005)Medical Devices—Application of Risk Management to Medical
Devices
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 cardiac cycle, n—defined as one cycle between diastolic and systolic pressures.from diastolic pressure to systolic pressure
and back to diastolic pressure.
3.1.2 compliance, n—the change in inner diameter of a vessel due to cyclic pressure changes. Compliance, if calculated, shall be
expressed as a percentage of the diameter change per 100 mm Hg mmHg and defined per ISO 7198, 8.10.5:A.5.9, or equivalently:
~Dp22 Dp1! ×10
%Compliance/100 mm Hg 5 (1)
Dp1 p22 p1
~ ~ !!
where:
Dp1 = inner diameter at the pressure of p1,
Dp2 = inner diameter at the pressure of p2,
p1 = lower pressure value (diastolic), in mm Hg, and
p1 = lower pressure value (diastolic), in mmHg, and
p2 = higher pressure value (systolic), in mm Hg.
p2 = higher pressure value (systolic), in mmHg.
3.1.3 diametric strain, n—a change in mock artery vessel or device diameter divided by the initial diameter. minimum diameter
at the measurement location. This term does not relateequate to the mechanical strain seen in the stentdevice material. The
diametric strain can be identified as:
Dp22 Dp1
~ !
diametric strain 5 (2)
Dp1
that is,
maxID 2 minID
~ !
diametric strain 5
minID
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
F2477 − 23
3.1.4 distension, endovascular prosthesis, n—the change in diameters; such as the inner diameter (ID) of a vessel due to a pressure
change. The term “diametric distension” is meant to represent the change in inner diameter of a blood vessel during each pulse
of blood circulation. As an example, the change in diameter between the diastolic and systolic pressure for each pulse of blood
circulation.vascular prosthesis (including modular components) which resides partially or completely within a blood vessel, or
vascular conduit to form an internal bypass or shunt between sections of the vascular system, delivered and deployed using a
delivery system (from ISO 25539-1). Examples of endovascular prostheses are vascular stent grafts and covered stents.
3.1.5 hydrodynamic loading, n—causing a change in the inner diameter (ID) of a mock vessel by injecting a volume of fluid into
the confined test volume.a confined test volume inside and/or outside the mock vessel.
3.1.6 mock vessel, n—a simulated vessel typically manufactured from an elastomeric material. The mock vessel is made to
approximate the ID and diametric distentionchange of a native vessel at physiological pressures (see A1.2.2 and A2.4.2) or at
non-physiological pressures (see A2.4.4). Mock vessels with a simulated aneurysm may be used when evaluating the pulsatile
durability of endovascular prostheses for aneurysmal exclusion indications. Mock vessels with a specified radius of curvature may
also be used.
3.1.7 native vessel, n—defined as a natural healthy blood vessel.
3.1.8 strain control, n—a term to describe control of diametric distention,change, relative to an initial diameter of the mock vessel,
not to be confused with controlling the strain in the stentdevice material.
3.1.9 vascular stent, n—a synthetic tubular structure that is implanted in the native or grafted vasculature and is intended to
provide mechanical radial support to enhance vessel patency over the intended design life of the device. A stent is metallic and
not covered by synthetic textile or tissue graft material. The term stent may also be used to describe the structural support
component(s) of an endovascular prosthesis.
4. Summary of Test Methods
4.1 This document details two test methods that are currently used: Pressure Test Method and Diameter Control Test Method.
These test methods cover fatigue/durability testing of vascular stents and endovascular prostheses that are subjected to
hydrodynamic loading (internal and/or external pressurization) that simulates the radial loading and/or change in diameter that the
stent will or prosthesis is expected to experience in vivo.vivo The stent due to the cyclic blood pressure changes of the cardiac cycle.
The stent or endoprosthesis shall be deployed into a mock vesselsvessel that can be used to produce a cyclic diameter change of
the stent. This document details two test methods that are currently used.stent or endoprosthesis. An endoprosthesis being evaluated
for an aneurysm exclusion indication may use a mock vessel with a simulated aneurysm. Within the aneurysmal sac portion of the
mock vessel, the endoprosthesis deformation is primarily due to cyclic pressure changes relative to the aneurysmal sac rather than
the simulated aneurysm dimensional changes. Thus, the mock aneurysmal sac compliance is not critical and pressure monitoring
of mock vessel might be needed.
4.1.1 Physiological Pressure Test Method—This test method (provided in Annex A1) requires the use of mock vessels that possess
similar diametric compliance properties to native vessels at physiological pressure and rate of pulsation as well as at higher testing
frequencies.(except within the mock aneurysm, if applicable) at specified physiologic pressures (applied externally and/or
internally) at the testing frequency. The use of physiologic transmural pressure (that is, external to internal pressure differential)
is important to ensure the test mimics physiological loading conditions. This test method may also be used with external
physiologic pressures applied to thin non-physiologic mock vessels.
4.1.2 Diameter Control Test Method—(Sometimes called a strain control test method.) This test method (provided in Annex A2)
requires the use of a diameter measurement system and mock vessels to ensure that the desired minimum and maximum
stentdevice diameters, or the equivalent change in stentdevice diameter and mean stentdevice diameter, are being achieved at the
test frequency. For conditions where a direct measurement of the stentdevice is not possible, measurements are typically made over
the OD outside diameter (OD) of the mock vessel and a relationship is determined and justified for the ratio of the stentdevice OD
versus measured mock vessel OD.
F2477 − 23
5. Specimen Size, Configuration, and Preparation Sample Preparation, Device Labeled Size, Sample Configuration,
Mock Vessels, and Number of Samples
5.1 Unless otherwise justified, all samples selected for testing shall be taken from fully processed,processed implant quality
product. Sterilization should be required, unless it can be shown not to influence the fatigue/durability test results.
5.2 The number of samples tested for each device geometry should be sufficient to support any claims to be made based on the
test results. The number of samples should also be justified in the context of the device risk assessment (see Guide F3172 and ISO
14971).
5.3 The number of specimens tested for each stent geometry should be sufficient to support any claims to be made based on the
test results. Fatigue/durability shall be evaluated for the worst case worst-case labeled diameter, and a rationale shall be provided
stating why the particular labeled diameter is considered worst case. See Guide F2514 for guidance in using finite element analysis
for radial loading of stents.
5.4 Mock Vessels:
5.4.1 The choice of inside diameter of the mock vessel in contact with the device is critically important to the effectiveness of any
durability test to be carried out. test. The mean non-stented mock vessel IDmock vessel diameter in contact with the device over
a cardiac cycle shallshould be consistent with the worst case stent OD, for the stentworst-case device diameter for the device being
tested, over the full test duration.
NOTE 1—If implementing fatigue-to-fracture testing, see Appendix X3 for guidance regarding the use of a liner within the mock vessel.
5.4.2 See Annex A1 and Annex A2Annex A1 and Annex A2 for specific requirements.
5.5 The sample size, number of samples, in combination with other tests, animal and clinical tests, analysis (suchanalyses such
as FEA (Finite Element Analysis), and/or comparisons to predicate devices shall be sufficient to enable demonstration of an
adequate justified reliability. In these test methods, one stent device or a pair of overlapped devices shall be considered one sample.
The reliability justification may reference additional testing and/or analysisanalyses used to establish stentdevice durability.
6. General Apparatus Requirements
6.1 For test methods requiring precision measurement and control of pressure, dimensions, or cycle counts, verification of the
dynamic performance of these systems at or encompassing the test frequency shall be performed and documented with justification
of the means used.
6.2 Pressure Measurement System—Pressure transducers shouldshall be chosen that allow for the accurate evaluation of the
pressures within the tubes applied pressures at the frequency of the test. pressures are to be measured. See Annex A1 and Annex
A2Annex A1 and Annex A2 for method specific requirements. The pressure measuring system must be calibrated and
justified.calibrated.
6.3 Dimensional Measurement Devices, such as linear variable displacement transducers, lasers, and high-speed cameras must be
calibrated and justified.
6.3 Cycle Counting System—The apparatus shall include a cycle counting system for measuring the number of load cycles applied
to the stent/mock arterydevice/mock vessel combination.
6.4 Temperature Control System—The apparatus shall include a calibrated temperature control and measurement system to provide
the testing temperature for stents being tested.devices being tested. If fluid temperature is measured to indicate device temperature,
the relationship between the fluid temperature at the associated measurement location and the device temperature shall be justified.
7. General Test Parameters
7.1 Temperature—The temperature of the device shall be 37 6 2°C. 2 °C. Normally this can be accomplished by controlling the
F2477 − 23
temperature of the fluid adjacent to the device. If other temperatures are to be used, a rationale shall be provided stating why the
particular temperature is considered worst case or equivalent. The unit is to be stable over the intended period of the test and
maintained within the established parameters.
NOTE 2—The presence of a mock vessel liner can induce a temperature differential between the fluid and device. This might require elevation of the fluid
temperature.
7.2 Actual temperatures and precisions shall be documented by the user with accompanying justifications.
7.3 Solutions—The test solution shall be phosphate buffered saline (PBS) or equivalent unless testing in a different environment
(such as in distilled water or in air) can be justified. Rationale for use of a different environment shall be provided.
7.4 Physiological Pressure—The pressure change in the intended blood vessel. A suggested range for coronary stent pulsatile
fatigue evaluation is 80 to 160 mm Hg.
NOTE 1—Selection of the systolic and diastolic pressures should be based on the patient population for which the stent is indicated.
7.5 Physiological Pulse Rate—For the purposes of these test methods, determined to be 1.2 Hz or 72 beats per minute.
7.2 Solutions—The test solution shall be physiologic pH buffered saline (for example, phosphate buffered saline) or equivalent
unless testing in a different environment (such as in 0.9 % saline, modified simulated body fluid, or Specification D1193 Class IV
distilled water) can be justified. Biological growth can inhibit post-test evaluation of the stentdevice surface characteristics. Use
of a biological growth inhibitor (such as algaecides or chemical agents) may be used unless such use would negatively impact the
test by unintended degradation of the stentdevice or the test set-up.setup. Rationale for use of a different environment shall be
provided.
7.3 Physiological Blood Pressures—The ID of the non-stented mock vessel is to be empirically verified on the test instrument after
the mock vessel(s) have been mounted in their initial test position.cyclic pressures in the intended blood vessel. Selection of the
systolic and diastolic blood pressures should be based on the patient population for which the device is indicated. For example,
suggested systolic and diastolic values for hypertensive arterial blood pressures are 160 and 80 mmHg.
7.4 Physiological Pulse Rate—For the purposes of these test methods, determined to be 1.2 Hz or 72 beats per minute.
7.5 Vessel Degradation—Mock vessels made of materials that may degrade with exposure to environmental factors (such as UV
light) shall be protected from such exposure.
7.6 StentDevice Deployment—The stentdevice shall be deployed in the mock vessel vessel, after tracking through a challenging
simulated anatomy, in such a manner as to minimize end effects where the vessel is connected to the test article and at a sufficient
distance from other stents that may be apparatus. Unless testing is to be conducted with devices overlapped, or as otherwise
justified, devices deployed in the same mock vessel (seeshall X2.5).be at a sufficient distance to avoid unintended interaction.
7.7 Test Duration—The test duration shall be justified. The number of cycles associated with an implantation time of ten years
(for example, for arterial stents at least 380 million cycles) has been historically used.
7.8 Test Frequency—See Annex A1 and Annex A2Annex A1 and Annex A2 for test specific test-specific details.
7.9 Test Validation—Device Deformation Verification—The Differences in the contact between the device and the mock vessel (for
example, no contact, too high friction, mock vessel conformability) compared to in vivoinvestigator shall demonstrate that the stent
to be tested maintains contact with the ID of the vessel to be used in the durability test throughout the cycle, when evaluated with
the same pressures and frequencies to be conditions can result in device deformation that is greater or less than intended. Thus,
the investigator should demonstrate that during the cyclic displacement the device is subjected to the intended deformation (for
example, similar deformation of device at 1.2 Hz) at the frequency and pressure used in the durability test. This is not required
may be done with a high-speed camera; however, a strobe light may also be used for qualitative verification. The high-speed
camera may be used to measure the change of the OD of the mock vessel. Imaging the device inside of the mock vessel is
F2477 − 23
problematic because of the refraction of light through different media (that is, air/silicone/water). See Appendix X2 for every
sample. This and any justifications shall be documented in the test report. Rationale: The additional details regarding measuring
the deformation of the device inside the mock vessel. Also, the proper functionality of a test method used to test a stentdevice inside
a mock vessel depends on the stentdevice remaining in contact with the ID of the vessel throughout the distension cyclediametric
change of that vessel. This is also true for endovascular prostheses used to treat occlusive disease. If evaluating an endovascular
prosthesis under aneurysmal conditions, the endovascular prosthesis should maintain contact with the mock vessel in the seal
regions, but not in the aneurysmal sac region. Thus, the investigator shall demonstrate that the device or endovascular prosthesis
to be tested maintains contact with the ID of the mock vessel to be used in the durability test throughout a test cycle, except in
the aneurysmal sac region of mock vessel being used to evaluate an endovascular prosthesis under aneurysmal conditions. Device
deformation verification is not required for every test sample. The number of devices used for the deformation verification should
be adequate and justified. The results of this verification activity should be used to establish the procedure for ensuring the intended
deformation of the test samples (for example, utilize test frequency that provides intended deformation). For example, if it can be
shown that the stroke and frequency of the pulsatile testing apparatus adequately correlates with the intended deformation of the
device, further deformation verification activities might not be needed. The completion of the device deformation verification and
any justifications shall be documented in the test report.
7.10 Variation of Loading Along Length as Function of Frequency—The investigator should be aware of the potential for pressure
variations along the length of a mock vessel that may change in location and magnitude as the test frequency is changed. Typically,
diastolic and systolic pressure levels are fairly uniform along the length of the mock vessel at physiologic frequencies, for example
1.2 Hz, but variation in the magnitude of either or both of these pressures along the length of the mock vessel can increase at
hyper-physiologic frequencies. The test frequency, tester design and configuration, as well as the mock vessel compliance, length
and diameter, and curvature can influence the magnitude of these pressure variations along the length of the mock vessel. The
pressure variations typically cause diametric strain variations along the length of the mock vessel. Stiffer mock vessels may be used
to reduce the diametric strain variations. However, in some cases prior to initiating cyclic fatigue, the investigator might find it
difficult to identify a test frequency (for example, during a frequency sweep) that is sufficiently high for a practical test duration
while maintaining acceptable pressure and/or diametric strain variability along the length of the mock vessel. In such cases, the
investigator may choose to identify region(s) of interest on the test sample where test pressures and/or diameters are to be
controlled, while other regions are only monitored. For example, the region(s) of interest would correspond to the location(s) that
have been identified through analysis as having the smallest fatigue safety factor.
7.11 Acceptance Criteria—Evaluation Procedure—A detailed test protocol shall be written that describes all procedures unique
to the stent device or endovascular prosthesis being evaluated. This protocol shall include any specific failure modes to be
identified, identified (for example, strut fracture, graft wear, fretting wear) and inspections to be performed to identify those failures
failures. Note, a known test artifact is the artifactual wear that can occur from interaction of the prosthesis with the mock vessel
material (for example, abrasion of graft material between silicone tube and device, rate-dependent abrasion properties of polymers)
which tend to be more abrasive, due to higher friction and inability to mimic in anyvivo acceptance/rejection criteria. (See
Appendix for examples.)remodeling, than human arteries.
8. Test Report
8.1 The test report shall include a complete summary of the materials, methods, and results including any rationale for deviations
from this procedure.standard. The effects of any such deviations on the significance of the test results shall be reported. All real,
artifact, and anomalous observations shall be reported, including a justification for considering negative findings as artifacts or
discounting their clinical significance.
8.2 Test reports should include:
8.2.1 Test parameters and acceptance criteria:
8.2.1.1 Test parameters (such as):
(1) Mock vessel dimensions.attributes (for example, ID at pressure, compliance).
(2) Fluid Device temperature or fluid temperature that has been previously correlated to device temperature.
(3) Regions of interest for diametric strain control and associated rationale.
(4) Fluid Control parameters (for example, fluid pressure range and variability, or desired change in stented vessel
diameter.vessel with device diameter).
(5) Minimum level and/or mean of control parameters (for example, diametric strain, pressure levels) across test samples.
F2477 − 23
8.2.1.2 Acceptance criteria (such as):
(1) Minimum level of pulsatile distention to define acceptance.
(1) Maximum number and location of failures to define acceptance.
(2) Allowable fracture grades (for example, SFA stent fracture grades).
(3) Minimum number of cycles required to define acceptance.
8.2.2 Test specimensample information:
8.2.2.1 Number of test specimens.samples.
8.2.2.2 Size (diameter, length, or other relevant dimensions) of all test specimens.samples.
8.2.2.3 Rationale for the number of test specimenssamples and sizes used.
8.2.2.4 Whether the specimenssamples are representative of the finished product.
8.2.2.5 Sterilization parameters and number of sterilization cycles applied to the test specimens.samples.
8.2.2.6 Traceability information.
8.2.2.7 Pre-conditioning status of samples (for example, loaded into a delivery catheter and tracked through a challenging
anatomy).
8.2.3 Materials used:
8.2.3.1 Test equipment.
8.2.3.2 Mock vessels.
8.2.3.3 Test fluid/solutions.
8.2.3.4 Measurement devices.
8.2.4 Test protocol, including all justifications and rationales required by these test methods.
8.2.5 Control values (for example, diametric strain, mean ID, alternating and mean pressure, temperature) and associated
tolerances.
8.2.6 Protocol deviations.
8.2.7 Raw data.Mean, standard deviation, minimum, maximum of measured load condition at each location monitored or
controlled for each sample at the specified measurement intervals (for example, 50 million, 100 million, 200 million, 380 million).
For ease of understanding, the use of a plot to present the associated data relative to applicable limits may be used.
8.2.7 Test results.
8.2.8 Data analysis
8.2.8 FractureDurability reporting:
8.2.8.1 Report any fractures that occur during the test.
8.2.8.2 Fracture information should include number of cycles to failure, number include: number and locations of all fractures
along the length of the stent,device, type of fracture such as transverse or spiral, with or without dislocation, and any root cause
analysis performed to determine the reason for the fracture. Report the number of cycles that were applied when the fracture was
identified or if available, report the number of cycles when the fracture occurred.
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8.2.8.3 Report durability observations other than fractures (for example, fretting wear between overlapped components).
8.2.8.4 For endovascular prostheses, report as applicable, observations of graft material wear, stent to graft attachment degradation
(for example, suture wear), or other observations relevant to the durability of the endovascular prostheses.
8.2.9 Conclusions.
9. Precision and Bias
9.1 Intralaboratory and interlaboratory reproducibility has not been systematically determined.No information is presented about
either the precision or bias of this test method for measuring durability since the test result is nonquantitative.
10. Keywords
10.1 durability test; endovascular cardiology; endovascular prostheses; fatigue test; interventional cardiology; intravascular device
test; pressure control; pulsatile fatigue; stent durability; stent fatigue; stent test; strain control; vascular stent
ANNEXES
(Mandatory Information)
A1. PHYSIOLOGICAL PRESSURE TEST METHOD FOR PULSATILE FATIGUE/DURABILITY TESTING OF
VASCULAR STENTS AND ENDOVASCULAR PROSTHESES
A1.1 Summary of Test Method
A1.1.1 With this technique, a fixed when the mock vessel is pressurized from the ID, a volume of fluid is injected into a fluid filled
fluid-filled mock vessel that has been manufactured to provide a targeted physiological dynamic diametric compliance. The
injected volume is adjusted so that the measured cyclic pressure rangedifferential is equivalent to the targeted physiological
pressures. The primary measurements made with this apparatus are the cyclic pressure, test frequency, cycle count, and
temperature. (See general test parameters.)pressure differential. The volume of fluid may also be injected into a fixed-volume
chamber surrounding the mock vessel to pressurize the OD of the vessel. With external physiologic pressures applied, thin mock
vessels may be used in lieu of physiological compliant mock vessels.
A1.2 Significance and Use
A1.2.1 This test method is used to determinecharacterize the durability of a stent under pulsatile vascular or endovascular
prosthesis under simulated vascular pulsatile conditions, to assess conformance to product specifications and guidance documents,
and it may be used to support regulatory submissions, quality control, and manufacturing.manufacturing (for example, process
changes).
A1.2.2 The success of this test This method depends on the use of a vessel that possesses physiologically relevant ID and diametric
compliance at physiologically relevant frequencies as well as at higher testing frequencies.controlled physiologic pressures and
either physiologic compliant vessels or with externally applied pressures mock vessels that are thin and do not appreciably inhibit
intended cyclic diametric deformation of the device.
NOTE A1.1—With externally applied pressures and thin mock vessels, the cyclic diametric deformation to the device might be greater than the expected
in vivo deformation.
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A1.3 Apparatus
A1.3.1 See Section 6 for general apparatus requirements.
A1.3.2 Loading—Fatigue/Durability Testing System—Specimen is deployed into a mock vessel that is then mounted onto a
fatigue/durability testing system that can deliver quantifiable pressures to the vessel.The system must be able to deliver quantifiable
pressures to the mock vessels at the desired test frequency and maintain the device temperature as specified (for example, 37 6
2 °C).
A1.3.3 Dynamic Compliance Measurement System—In this test method, a replication of the loading conditions that occurThe
apparatus should include a diameter measuring system that allows in vivodetermination requires the choice of a vessel that has of
the ID and diametric compliance properties possessed by the target vessel. Once a stent is deployed into a native or mock vessel
with these properties, a cyclic pressurization of that vessel will cause the vessel to expand. At the same time, the amount of
compressive loading that the vessel is applying to the stent is reduced in proportion to the increase in internal pressure. This
repeated pressurization is the mechanism by which the stents are cyclically loaded. It is important that pressure be regularly
monitored throughout the testing. In order to account for viscoelastic behavior of the mock vessel, the compliance of the mock
vessel is evaluated at 72 beats per minute, and at the testing frequency that is to be utilized for the durability testing. The maximum
test frequency may be limited by the dynamic response of the vessel.dynamic compliance of the mock vessels used in this method
and is able to apply controlled cyclic physiologic pressures. This system may be the same apparatus as the fatigue/durability testing
system. The system must operate such that the cyclic diameters and pressures can be measured at the test frequency.
NOTE A1.2—If direct measurement of the ID of the mock vessel is not possible with measurement system used, an empirical method may be used to relate
the deployed device outer diameter (OD) with the measured mock vessel outer diameter (OD) as found in Appendix X2.
A1.4 Procedure
A1.4.1 Determine When a physiologic compliant vessel is intended to be used, determine the ID and ID dynamic (1.2 Hz)
compliance of the physiological mock vessel over the desired pressure range (80 to 160 mm Hg unless otherwise justified) at the
frequency of test to be used as at the desired test frequency over the justified physiologic pressure range. The method (direct OD
measurement only) outlined in ISO 7198 (load-controlled testing). The mean ID shall be determined as well as the compliance.
The mean ID is determined to ensure conformity with 7198:2016 clause A.5.9 may be used, with exception of the tension applied.
The mock vessels should be tensioned uniformly (from vessel to vessel) and as they will be during cyclic testing. Length (pre and
post tensioned) may be used to set the tension. Tensioning the mock vessel reduces the ID and increases the diametric compliance.
The pressure transducer(s) shall be placed at 5.3.1. If multiple vessels are used, ensure that the mock vessels are mounted under
uniform tension. Rationale: The mock vessel ID may be reduced and the radial the location of diameter measurements or a location
that has been validated at the test frequency. The ID and dynamic compliance may be increased if the mock vesseldetermined using
one of the options in Appendix X2were to be mounted under tension on the test instrument (see. These values are measured to
ensure the desired radial loading 7.5).is applied to the device.
NOTE A1.3—When external physiologic pressures applied and thin mock vessels are used, the compliance of the mock vessel does not need to be
measured. However, the mock vessels must be thin enough to allow the applied external pressure to be transferred to the device as intended.
A1.4.2 Deploy the stentdevice in the mock vessel following instructions for use. For temperature-dependent devices, deployment
at 37 6 2 °C might be necessary to ensure a clinically representative deployment. Leave enough length of the mock vessel
extending beyond each end of the test article device such that the test article device will be in the region where the required
compliance is valid, device deformation is unaffected by any end effects imposed by the fatigue/durability test system (see
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system.7.7). Re-measure dynamic (1.2 Hz) compliance using mounting tension similar to that used for the non-stented dynamic
compliance measurements. Verify that this composite (stent and vessel) compliance is maintained at the desired test frequency.
A1.4.3 Inspect the deployed stents in a systematic and objective manner, using appropriate instruments or techniques, and record
the location and severity of any anomalies. Document the inspection locations for correlation to post test post-test inspection (see
A1.6.2).
A1.4.4 Record proximal and distal locations of each installed device in the mock vessel prior to beginning the test.
A1.4.5 Establish the tolerances associated with the cyclic physiologic pressures. Tolerances may be set for the pressure amplitude
and pressure mean, or alternatively the maximum and minimum pressure. Tolerances do not need to be bilateral.
NOTE A1.4—Tolerance cumulation should be considered when assigning tolerances. For example, when setting tolerances on the minimum and maximum
pressure, the impact of tolerance cumulation on the pressure amplitude and pressure mean should be understood.
A1.4.6 Install each mock vessel/stent assembly onto the fatigue/durability test system using tensioning similar to that used for the
dynamic compliance measurements and fill the system with the test solution. Purge trapped air from the system. Activate As
appropriate, activate the temperature control system and allow the test system to equilibrate at 37 6 2°C2 °C (unless otherwise
justified).
A1.4.7 Start the fatigue/durability test system and adjust the frequency to the desired rate and adjust the cyclic pressure range to
justified physiological levels (80 to 160 mm Hg should be used unless otherwise justified). Determine the maximum test frequency
that provides mock vessel distension uniformity comparable to that measured at the physiological rate (72 bpm or 1.2 Hz).
Document non-uniformities in vessel distension at test frequency and provide rationale for acceptable use at that frequency.within
tolerance of the justified physiological levels. Ensure the deformation of the device is as desired at the test frequency. If not, an
alternative frequency may be needed.
A1.4.8 Zero the counter.
A1.4.9 Verify the pressures at justifiable time intervals.Periodically monitor and document the cyclic pressures at prospectively
specified intervals. Adjust the system as necessary to maintain the cyclic pressures within tolerance. If the cyclic pressures are
out-of-tolerance, the cycles between the last in-tolerance measurement and when the system was brought back to within tolerance,
for any given test sample, shall not be counted toward the number of cycles required for test termination.
NOTE A1.5—It can be prudent to specify an additional set of tighter tolerances for system adjustment to keep centered within the cyclic pressure tolerances
(that is, warning limits).
A1.4.10 If desired, carry out periodic inspections of the instrument and stent. device. If the stentdevice is removed from the mock
vessel for inspection, care must be taken to remove and re-deploy it in a manner that does not destroy the integrity of the test.
Periodic inspection, or lack of inspection, inspection shall be at the discretion of the stent manufacturer and justified in the
report.device manufacturer.
A1.4.11 Periodically re-measure the When a physiologic compliant vessel is intended to be used and the mock vessels have not
been previously validated to have acceptable change in compliance and ID, periodically re-measure the ID and dynamic
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compliance of the deployed stent/vessel systems in addition to the mock vessel mean ID mock vessel at the test frequency. The
pressure transducer(s) shall be placed at the location of diameter measurements or a location that has been validated at the test
frequency. This may be important as it checks for can identify any change in loading or experimental properties that might be
occurring. Determine if the change is due to a change in the test article or the mock vessel. If the change is in the mock vessel,
re-deploy the stentthat can occur. If unacceptable changes occur, and if possible, without impacting the results of the test, replace
the mock vessel (that is, move the device to a new mock vessel) preferably without re-deployment of the device. If moving the
device to a new mock vessel and continue the test. If it is determined that the change in compliance is due to a change in the test
article itself, continue the test without changing the mock vessel. Provide justification for measurements and any mock vessel
changes.is not possible, a new device and mock vessel might need to be tested.
A1.5 Test Termination
A1.5.1 Continue to test until the required number of cycles (at the in-tolerance cycles (for example, at least 380 million cycles
for a 10 year test) has been applied to each stent.test representative of ten years implantation) has been applied.
A1.6 Post Test Post-Test Inspection
A1.6.1 Re-measure the dynamic compliance and the When a physiologic compliant vessel is intended to be used and if the mock
vessels have not been previously validated to have acceptable change in compliance and ID over the duration of the test,
re-measure the compliance and the mean inner diameter of the deployed stent/vessel systems mock vessel at the test frequency
when the test is complete.
A1.6.2 Inspect all stentsdevices as required in the protocol.
A2. DIAMETER CONTROL TEST METHOD FOR PULSATILE FATIGUE/DURABILITY TESTING OF VASCULAR STENTS
AND ENDOVASCULAR PROSTHESES
A2.1 Summary of Test Method
A2.1.1 The purpose of this test method is to reproduce the desired minimum and maximum diameters, or equivalent change in
diameter at a mean, that the stentdevice would see in vivo. To reproduce these diameters, a volume of testing fluid is cyclically
injected into a fluid filled fluid-filled mock vessel that may or may not have a compliance that is physiologically relevant. Thick
walled Alternatively, the volume of fluid could be cyclically injected into a fixed-volume chamber surrounding the mock vessel
to pressurize the OD of the vessel that contains fluid. Thick-walled (thicker than physiological tubing walls) mock vessels are
commonly used in order to achieve the desired higher frequency levels. The injected volume is adjusted so that the minimum
diameter and maximum diameter of the stentdevice is equivalent to the minimum and maximum diameters that the stentdevice
would experience under physiological conditions. The desired primary measurements made with this test method are the OD (outer
diameter) of the stent,device, test frequency, cycle count, and temperature, if necessary. If direct measurement Measurement of the
OD of the stent is not possible, an empirical method may be used to relate the deployed stent OD with device using optical methods
is problematic due to the lensing effect of the cylindrical mock vessel. Thus, the deployed device OD may be equated to the mock
vessel inner diameter (ID). (ID) and a relationship between the OD and the ID of the mock vessel may be used. Several methods
for determining the relationship of the OD of the stented mock vessel to the mock vessel ID are provided in X2.5Appendix X2.
The relationship between the OD and ID of the mock vessel used for this purpose shall be justified.
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A2.2 Significance and Use
A2.2.1 This test method is used to determinecharacterize the durability of a stent under pulsatile vascular or endovascular
prosthesis under simulated vascular pulsatile conditions, to assess conformance to product specifications and guidance documents,
and it may be used to support regulatory submissions, quality control, and manufacturing.manufacturing (for example, process
changes).
A2.2.2 The success of this test method depends upon the use of a diameter measurement system that ensures helps ensure that the
desired minimum and maximum diameters, or equivalently, the desired mean diameter and change in diameter, of the stentsdevices
are being achieved at all testing frequencies.the testing frequency.
A2.3 Apparatus
A2.3.1 See Section 6 for general apparatus requirements.
A2.3.2 Diameter Measurement System—The apparatus should include a diameter measuring system that measures the resulting
allows the determination of the cyclic change in diameter of the stents devices at the area of interest within the mock vessel. If
direct measurement of the OD of the stent is not possible, an empirical method may be used to relate the deployed stent outer
diameter (OD) with the measured mock vessel outer diameter (OD). This measurement may be made by measuring the outer
diameter (OD) of
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