ASTM F2079-09(2013)
(Test Method)Standard Test Method for Measuring Intrinsic Elastic Recoil of Balloon-Expandable Stents
Standard Test Method for Measuring Intrinsic Elastic Recoil of Balloon-Expandable Stents
SIGNIFICANCE AND USE
4.1 Minimal stent recoil is a desirable feature of a stent because it minimizes the maximum diameter to which a stent must be expanded to achieve its final relaxed diameter. A stent having a high recoil must be expanded to a greater diameter to achieve its final relaxed diameter than a stent having low recoil. Practically, excessive expansion of the vessel into which the stent is to be implanted may cause tissue damage resulting in a poor immediate result or poor long-term outcome. Stent recoil is affected by intrinsic properties of the material used to construct the stent and the specific geometric design of the stent; therefore, measuring stent recoil is an essential part of evaluating the design.
SCOPE
1.1 The purpose of this test method is to quantify the percentage by which the diameter of a stent decreases from its expanded diameter while still on the delivery balloon to its relaxed diameter after deflating the balloon. This test method is appropriate for stents manufactured from a material that is plastically deformed when the stent's diameter is increased from its predeployed size to its postdeployed size by mechanical means. This test method may be performed in air at room temperature unless there is a known temperature dependence of the material, in which case, the temperature at which the test is conducted shall be stated in the report.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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.
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Designation: F2079 − 09 (Reapproved 2013)
Standard Test Method for
Measuring Intrinsic Elastic Recoil of Balloon-Expandable
Stents
This standard is issued under the fixed designation F2079; 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 The outer diameter of the stent is measured in at least three
axial locations while the stent is still on the inflated delivery
1.1 The purpose of this test method is to quantify the
balloon.At each axial location, measurements are taken in two
percentage by which the diameter of a stent decreases from its
approximately orthogonal rotational positions. The balloon is
expanded diameter while still on the delivery balloon to its
deflated and the outer diameter of the stent is remeasured in the
relaxed diameter after deflating the balloon.This test method is
same positions at approximately the same locations.
appropriate for stents manufactured from a material that is
plastically deformed when the stent’s diameter is increased
4. Significance and Use
from its predeployed size to its postdeployed size by mechani-
cal means. This test method may be performed in air at room
4.1 Minimal stent recoil is a desirable feature of a stent
temperatureunlessthereisaknowntemperaturedependenceof
because it minimizes the maximum diameter to which a stent
the material, in which case, the temperature at which the test is
must be expanded to achieve its final relaxed diameter.Astent
conducted shall be stated in the report.
having a high recoil must be expanded to a greater diameter to
achieve its final relaxed diameter than a stent having low
1.2 The values stated in SI units are to be regarded as
recoil. Practically, excessive expansion of the vessel into which
standard. No other units of measurement are included in this
the stent is to be implanted may cause tissue damage resulting
standard.
in a poor immediate result or poor long-term outcome. Stent
1.3 This standard does not purport to address all of the
recoil is affected by intrinsic properties of the material used to
safety concerns, if any, associated with its use. It is the
construct the stent and the specific geometric design of the
responsibility of the user of this standard to establish appro-
stent; therefore, measuring stent recoil is an essential part of
priate safety and health practices and determine the applica-
evaluating the design.
bility of regulatory limitations prior to use.
5. Apparatus
2. Terminology
5.1 Ameans to inflate with noncompressible fluid, typically
2.1 Definitions:
water, the delivery balloon on which the stent is mounted. The
2.1.1 labeled diameter, n—the nominal deployed size of a
means used must be capable of achieving the pressure required
stent as indicated on its manufacturer’s label.
to maintain the expanded diameter of the stent until it can be
2.1.2 stent recoil, n—the amount, expressed as a percentage,
measured and may include a device to monitor pressure.
by which the diameter of a stent changes from the expanded
diameter measured with the stent on the inflated delivery
5.2 A means to measure the outer diameter of the stent
balloon to the final value measured after deflating the balloon.
without deforming the stent. Typically, a calibrated optical
system, which does not require contact with the stent, is used.
3. Summary of Test Method
The resolution of the measurement system shall be 0.01 mm or
3.1 A sample device representative of product that will be better. The accuracy of the system shall be 2 % of reading or
marketed is either premounted or mounted on the delivery better.
balloon at the time of use. The delivery balloon is inflated to
the nominal expansion pressure indicated for the labeled stent. 6. Sampling, Test Specimens, and Test Units
6.1 Unless otherwise justified, all samples selected for
testing should be taken from fully processed, clinical quality
This test method is under the jurisdiction ofASTM Committee F04 on Medical
and Surgical Materials and Devices and is the direct responsibility of Subcommittee
product. It is not required that these devices undergo terminal
F04.30 on Cardiovascular Standards.
sterilization.Cosmeticrejectsorothernonclinicalsamplesmay
Current edition approved March 1, 2013. Published March 2013. Originally
be used if the cause for rejection has been shown not to affect
approved in 2001. Last previous edition approved in 2009 as F2079 – 09. DOI:
10.1520/F2079-09R13. stent recoil.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2079 − 09 (2013)
6.2 The number of specimens tested for each unique stent the measurement system as in 7.4. These measurements should
geometry should be sufficient to meet sampling requirements be taken no sooner than 10 s after deflating the balloon.
for desired specification limits. In general, a minimum of ten
8. Calculation
specimens is recommended. If a single stent geometry is
8.1 Calculate the stent recoil for the locations measured in
intended to be used for more than one labeled diameter, recoil
7.4 for each stent using the following equation:
shall be evaluated for test specimens expanded to the smallest
and largest diameters intended for that geometry.
Diameter
final
Stent Recoil % 5 1 2 *100 (1)
~ ! S S DD
Diameter
6.3 Most stents are comprised of a repetitious continuous inflated
pattern or of repeating subunits. If stents are made longer by
where:
additional r
...
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