ASTM F3067-14
(Guide)Guide for Radial Loading of Balloon Expandable and Self Expanding Vascular Stents
Guide for Radial Loading of Balloon Expandable and Self Expanding Vascular Stents
SIGNIFICANCE AND USE
4.1 Upon deployment, at the site of the vascular stenosis, the stent establishes the patency of the lumen until vascular remodeling occurs. The radial load acting upon the stent is imparted by vessel and lesion stretch. Additionally, the vessel might be affected by excursions due to pulsation (systolic and diastolic variation), muscle-skeletal interactions due to patient movement, as well as external sources (e.g., patient is struck in the neck during a car accident). The excursions vary in magnitude and type based on the location of the vessel.
4.2 In order to maintain vessel patency, the stent has to withstand the forces acting on it without experiencing excessive deformation, migration, or sustained collapse; therefore, it is required that the stent possess adequate resistance to these loads.
4.3 Depending on the type of device and the clinical concern, the resistance to these loads can be presented through multiple test outputs: radial strength, collapse pressure, or chronic outward force.
4.4 The guidelines presented here can be used in the development of test methods to determine the radial loading properties of stents. This guide provides examples of different test apparatus (equipment and tooling), radial loading curves, and calculations. Although the apparatus and methods presented can be used as a reasonable simulation of actual clinical use, they have not been demonstrated to predict the actual in vivo clinical performance of any stent.
SCOPE
1.1 This document provides guidance for developing in vitro test methods for measuring the radial strength or collapse pressure of balloon-expandable vascular stents and chronic outward force of self-expanding vascular stents.
1.2 This guide is applicable to balloon-expandable and self-expanding stents of tubular geometry. It covers both stent and stent grafts. It does not cover bifurcated stents. It does not cover stents with non-circular cross-sections or tapered stents.
1.3 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This guide does not recommend any specific test method or apparatus for measuring the radial strength, collapse pressure, or chronic outward force. Instead, this guide provides examples of test methodologies and equipment that could be used and recommends the format for presenting test results.
1.5 This guide covers only in vitro bench testing methods. In vivo behavior might be different.
1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Standards Content (Sample)
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Designation: F3067 − 14
Standard Guide for
Radial Loading of Balloon Expandable and Self Expanding
1
Vascular Stents
This standard is issued under the fixed designation F3067; 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 F2477 Test Methods for in vitro Pulsatile Durability Testing
of Vascular Stents
1.1 This document provides guidance for developing in
vitro test methods for measuring the radial strength or collapse
3. Terminology
pressure of balloon-expandable vascular stents and chronic
outward force of self-expanding vascular stents.
3.1 Definitions (alphabetically listed):
1.2 This guide is applicable to balloon-expandable and 3.2 balloon-expandable stent—a stent that is expanded at
self-expanding stents of tubular geometry. It covers both stent the treatment site by a balloon catheter. The stent material is
and stent grafts. It does not cover bifurcated stents. It does not plastically deformed by the balloon expansion such that the
cover stents with non-circular cross-sections or tapered stents. stent remains expanded after deflation of the balloon.
1.3 Units—The values stated in SI units are to be regarded 3.3 chronic outward force—the minimum continued open-
ing force of a self-expanding stent acting on the vessel wall at
as standard. No other units of measurement are included in this
standard. a specified diameter. The range of chronic outward force is
defined by the unloading curve at the maximum and minimum
1.4 Thisguidedoesnotrecommendanyspecifictestmethod
indicated use diameters. Additional loading force consider-
or apparatus for measuring the radial strength, collapse
ations for self-expanding stents are evaluated as load excur-
pressure, or chronic outward force. Instead, this guide provides
sions and described in Appendix X2. Chronic outward force is
examples of test methodologies and equipment that could be
not defined for balloon-expandable stents.
used and recommends the format for presenting test results.
3.4 collapse pressure—the uniform radial load during test-
1.5 This guide covers only in vitro bench testing methods.
ing with a hydraulic or pneumatic apparatus in which a
In vivo behavior might be different.
balloon-expandable stent undergoes buckling over a specific
1.6 This standard does not purport to address all of the
region or the entire stent length.
safety concerns, if any, associated with its use. It is the
3.5 load—a normalized, scalar value of force applied by the
responsibility of the user of this standard to establish appro-
stenttothevesseland,atequilibrium,thevesseluponthestent.
priate safety and health practices and determine the applica-
Load should be normalized by length (newton or millinewton
bility of regulatory limitations prior to use.
per millimeter length) or by area (pascal or kilopascal).
3.6 loading line—for balloon-expandable stents, the line
2. Referenced Documents
derived from the substantially linear portion of the radial
2.1 ASTM Standards:
loading curve during initial compression. The term is not
E4 Practices for Force Verification of Testing Machines
defined for balloon-expandable stents tested using collapse
E177 Practice for Use of the Terms Precision and Bias in
pressure apparatus.
ASTM Test Methods
3.7 radial force—output of radial loading that equals the
F2079 Test Method for Measuring Intrinsic Elastic Recoil of
radialpressuretimesthestentcylindricalarea.Therelationship
Balloon-Expandable Stents
between radial force (F ) and radial pressure (P) is given in the
R
F2081 Guide for Characterization and Presentation of the
equation:
Dimensional Attributes of Vascular Stents
F
R
P 5
A
1
This guide is under the jurisdiction of ASTM Committee F04 on Medical and
where:
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.30 on Cardiovascular Standards.
P = radial pressure,
Current edition approved Oct. 15, 2014. Published March 2015. DOI: 10.1520/
F = radial force, and
R
F3067-14.
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F3067 − 14
3.16 unloading line—for balloon-expandable stents, the line
A = instantaneous stent cylindrical area:
derived from the substantially linear portion of the radial
A 5 πDL unloading curve. The term does not apply for balloon-
expandable stents tested using collapse pressure apparatus.
where:
3.17 vascular patency—ameasureoftheextenttowhichthe
D = instantaneous stent expanded outer diameter, and
vessel is open (unrestricted). Typically reported as a perc
...
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