ASTM F2081-06(2013)
(Guide)Standard Guide for Characterization and Presentation of the Dimensional Attributes of Vascular Stents
Standard Guide for Characterization and Presentation of the Dimensional Attributes of Vascular Stents
SIGNIFICANCE AND USE
4.1 Vascular stents are intended for permanent implant in the human vasculature (native or graft) for the purposes of maintaining vessel patency. The dimensional attributes of vascular stents are critical parameters that aid clinicians in the selection of devices for individual patients. This guide contains a listing of those dimensional attributes that are directly related to the clinical utility and performance of these devices, along with recommendations for consistent methods of measuring these attributes and presenting the information for use in clinical decision making. This guide can be used by the manufacturers and researchers of stents to provide consistency of measurement and labeling of these dimensional characteristics. It may have use in the regulation of these devices by appropriate authorities.
4.2 The dimensional attributes included in this guide are those that are deemed related to or possibly predictive of successful clinical performance of the stent, based on prior clinical experience; however, because of the myriad patient and medical factors that influence the clinical outcome of any individual treatment, conformance of a stent and delivery system with the recommendations in this guide should not be interpreted as a guarantee of clinical success in any individual patient or group of patients.
SCOPE
1.1 This guide covers the identification of and recommended measurement methods for those dimensional attributes of vascular stents that are deemed relevant to successful clinical performance. The delivery system packaged with and labeled specifically for use during the placement of the stent is also included within the scope of this guide.
1.2 This guide addresses only the dimensional characteristics of stents. Material property and stent functional characteristics are not addressed herein. All dimensional characteristics described in this guide refer to in vitro (“bench-top”) characterization. Because of variable patient factors, for example, vessel compliance, the actual in vivo characteristics may be slightly different.
1.3 This guide includes recommendations generally applicable to balloon-expandable and self-expanding stents fabricated from metals and metal alloys. It does not specifically address any attributes unique to coated stents or polymeric or biodegradable stents, although the application of this guide to those products is not precluded.
1.4 While they are not specifically included within the scope of this guide, stents indicated for placement in nonvascular locations, such as the esophagus or bile duct, also might be characterized by the methods contained herein. Likewise, this guide does not include recommendations for endovascular grafts (“stent-grafts”) or other conduit devices commonly used to treat aneurysmal disease or peripheral vessel trauma or to provide vascular access, although some information included herein may be applicable to those devices.
1.5 This guide does not include recommendations for balloon catheters sold as stand-alone angioplasty catheters, even though some of those catheters may be used for the delivery of unmounted stents supplied without a delivery system. Requirements for angioplasty catheters are contained in standards ISO 10555-1 and ISO 10555-4.
1.6 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.6.1 The units of measurements used throughout this guide reflect the hybrid system in common clinical use in the United States as of the time of the original approval of this guide. Since a primary purpose of this guide is to promote uniformity of labeling to facilitate the selection of devices by clinical users, the units most preferred by users w...
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Designation: F2081 − 06 (Reapproved 2013)
Standard Guide for
Characterization and Presentation of the Dimensional
Attributes of Vascular Stents
This standard is issued under the fixed designation F2081; 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 1.6 The values stated in either SI units or inch-pound units
are to be regarded separately as standard. The values stated in
1.1 This guide covers the identification of and recom-
each system may not be exact equivalents; therefore, each
mended measurement methods for those dimensional attributes
system shall be used independently of the other. Combining
of vascular stents that are deemed relevant to successful
values from the two systems may result in non-conformance
clinical performance. The delivery system packaged with and
with the standard.
labeled specifically for use during the placement of the stent is
1.6.1 The units of measurements used throughout this guide
also included within the scope of this guide.
reflect the hybrid system in common clinical use in the United
1.2 This guide addresses only the dimensional characteris-
States as of the time of the original approval of this guide.
tics of stents. Material property and stent functional character-
Since a primary purpose of this guide is to promote uniformity
istics are not addressed herein. All dimensional characteristics
of labeling to facilitate the selection of devices by clinical
described in this guide refer to in vitro (“bench-top”) charac-
users, the units most preferred by users were selected for this
terization. Because of variable patient factors, for example,
guide. Where those units are not SI units, or derivatives
vessel compliance, the actual in vivo characteristics may be
thereof, SI units are provided in parentheses.
slightly different.
2. Referenced Documents
1.3 This guide includes recommendations generally appli-
cable to balloon-expandable and self-expanding stents fabri-
2.1 ISO Standards:
cated from metals and metal alloys. It does not specifically
ISO 10555-1, Sterile, Single-Use Intravascular Catheters,
address any attributes unique to coated stents or polymeric or
General Requirements
biodegradable stents, although the application of this guide to
ISO 10555-4, Sterile, Single-Use Intravascular Catheters—
those products is not precluded.
Balloon Dilation Catheters
1.4 Whiletheyarenotspecificallyincludedwithinthescope
3. Terminology
of this guide, stents indicated for placement in nonvascular
locations, such as the esophagus or bile duct, also might be
3.1 Definitions of Terms Specific to This Standard:
characterized by the methods contained herein. Likewise, this
3.1.1 balloon-expandable stent, n—a stent that is expanded
guide does not include recommendations for endovascular
at the treatment site by a balloon catheter. The stent is altered
grafts (“stent-grafts”) or other conduit devices commonly used
permanently by the balloon expansion such that the stent
to treat aneurysmal disease or peripheral vessel trauma or to
remains expanded after deflation of the balloon.
provide vascular access, although some information included
3.1.2 bridge, n—a connecting element between the radial
herein may be applicable to those devices.
support aspects of a stent. A bridge may have unique design
1.5 This guide does not include recommendations for bal-
features, as compared to a strut, to enhance longitudinal
loon catheters sold as stand-alone angioplasty catheters, even
flexibility and minimize shortening.
though some of those catheters may be used for the delivery of
3.1.3 crimp, v—tosecurethestentonthedeliverysystemby
unmounted stents supplied without a delivery system. Require-
compressing the stent onto the balloon. Stents sold unmounted
ments for angioplasty catheters are contained in standards ISO
must be crimped manually by the clinical staff before use.
10555-1 and ISO 10555-4.
3.1.4 crossing profile, n—a linear measure of the maximum
breadth of the stent/delivery system over the distal-most region
This guide is under the jurisdiction of ASTM Committee F04 on Medical and
of the delivery system.
Surgical Materials and Devicesand is the direct responsibility of Subcommittee
F04.30 on Cardiovascular Standards.
Current edition approved March 1, 2013. Published March 2013. Originally
approved in 2001. Last previous edition approved in 2006 as F2081 – 06. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/F2081-06R13. 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
F2081 − 06 (2013)
3.1.5 delivery system, n—asystemthatisusedtodeliverand of measurement and labeling of these dimensional character-
deploy a stent at the target site. A delivery system may be istics. It may have use in the regulation of these devices by
similar to a balloon dilatation catheter; a delivery system for a appropriate authorities.
self-expanding stent might not have a balloon.
4.2 The dimensional attributes included in this guide are
3.1.6 diameter, n—refers to the inside diameter (ID) of the
those that are deemed related to or possibly predictive of
stent unless otherwise noted.
successful clinical performance of the stent, based on prior
clinicalexperience;however,becauseofthemyriadpatientand
3.1.7 diameter, labeled, n—single value representation of
medical factors that influence the clinical outcome of any
intended-use diameters, typically rounded to nearest 0.25 or
individual treatment, conformance of a stent and delivery
0.5 mm. The labeled diameter is within the range recom-
system with the recommendations in this guide should not be
mended in the Instructions for Use (IFU) for that particular
interpreted as a guarantee of clinical success in any individual
stent and delivery system.
patient or group of patients.
3.1.8 percent solid area, n—that percentage of the projected
cylindrical side surface area (π times outside diameter times
5. Classification
length at labeled diameter) that is covered by stent material,
when the stent is expanded to its labeled diameter. 5.1 Stentsmaybeclassifiedbythefollowingcharacteristics,
as defined in Section 3.
3.1.9 premounted stent, n—a stent supplied by a manufac-
5.1.1 Mounting—Premounted or unmounted.
turer already mounted on a delivery system.
5.1.2 Expansion—Balloon expandable or self-expanding.
3.1.10 self-expanding stent, n—a stent that expands without
extrinsic force or pressure, to a size and shape close to the
6. Test Devices and General Procedures
desired final size and shape, when released from the delivery
6.1 Unless otherwise justified, all samples selected for
system. The self-expanding nature of some stents is a design
feature resulting from the materials of construction or the testing or measuring the attributes described in this guide
should be taken from finished, clinical-quality product. Cos-
structural geometry, or both.
metic rejects or other nonclinical samples may be used if the
3.1.11 sheath, n—a movable cover that constrains a self-
cause for rejection is not related to the attribute being assessed.
expanding stent on the delivery system until its desired release
Sterilization can be omitted if it can be demonstrated that
or protects a balloon-expandable stent during delivery before
sterilization has no affect on the attribute being assessed.
deployment.
6.2 When specimen preparation (for example, manual
3.1.12 shortening/lengthening, n—the percentage change in
crimping onto a delivery system, balloon expansion), is re-
length between the undeployed mounted condition and the
quired before testing, this should be done in accordance with
expanded labeled-diameter condition.
the Instructions for Use (IFU).
3.1.13 stent, vascular, n—asynthetictubularstructurethatis
6.3 The preconditioning and test environments must be
permanently implanted in the native or grafted vasculature and
that is intended to provide mechanical radial support to appropriately selected for each design and attribute. Tempera-
ture and fluid immersion may have a significant effect on some
enhance vessel patency. For the purposes of this guide, a stent
is metallic and not covered by synthetic textile or tissue graft attributes but a negligible affect on others. For example, fluid
sorption may swell catheters and affect the measurement of
material.
crossing profile. Temperature may affect the final deployed
3.1.14 strut, n—the smallest individual element of the radial
diameter for stents made from shape memory materials. For
support aspect of a stent that has a solid cross section in both
measurementsforwhichdeployment,ormeasurement,orboth,
the radial and circumferential directions.
is to be made in a controlled environment, the stent or delivery
3.1.15 unmounted stent, n—a stent that is not crimped on a
system, or both, should be immersed in a water bath main-
delivery system as supplied by the manufacturer. Before use,
tained at 37 6 2°C and allowed to equilibrate.
the clinical staff must manually crimp unmounted stents onto a
6.4 The number of specimens evaluated for each diameter
delivery device.
for each stent design should be sufficient to meet the sampling
requirementsforthedesiredlabeling.Ingeneral,aminimumof
4. Significance and Use
ten replicate test devices of each size to be measured or tested
4.1 Vascular stents are intended for permanent implant in
is recommended. If a single stent design is intended to be
the human vasculature (native or graft) for the purposes of
deployed over a broad range of diameters by use on different
maintaining vessel patency. The dimensional attributes of
size delivery systems, the dimensional attributes should be
vascular stents are critical parameters that aid clinicians in the
evaluated for each stent/delivery system combination.
selection of devices for individual patients.This guide contains
a listing of those dimensional attributes that are directly related
7. Dimensions and Measurement Methods
to the clinical utility and performance of these devices, along
with recommendations for consistent methods of measuring 7.1 Deployed Diameter—Unless otherwise specified, all
these attributes and presenting the information for use in deployed diameters refer to the inside diameter, reported in
clinical decision making. This guide can be used by the millimetres to the nearest 0.1 mm, after balloon deflation (for
manufacturers and researchers of stents to provide consistency balloon-expandable stents).
F2081 − 06 (2013)
7.1.1 Measurement—The outside diameter of deployed lengthening should be reported as a percentage of the mounted
stents should be measured by noncontacting instruments (pro- (undeployed) length to the nearest 1 %.
file projector, laser micrometer, and so forth) with a resolution
7.3 Crossing Profile:
of 0.05 mm or better. Inside diameter can then be calculated by
7.3.1 Measurement—With the stent premounted or hand-
subtracting twice the wall thickness (7.4). Alternatively, the
crimped on the delivery system in accordance with the instruc-
inside diameter can be measured by calibrated gauges.
tions for use, and the sheath (if any) in place, measure the
7.1.2 Labeled Diameter—The labeled diameter is that used maximum diameter over the length from the proximal end of
to identify the typical deployed size of a particular device, for
the mounted stent to the distal tip of the delivery system. A
example, 3.0 mm or 3.5 mm, and must be clearly identified as minimum of ten replicate test articles should be measured. The
inside or outside diameter (ID or OD). ID is preferred. The
measurement instrument should be either noncontacting (opti-
labeled diameter is usually rounded to the nearest 0.25 or 0.5 cal profilometer, laser micrometer, and so forth) or a ring/hole
mm. gage, and should have a resolution of 0.001 in. [0.025 mm] or
better. The crossing profile should be reported as the mean
7.1.3 Stent System Compliance—For balloon-expandable
measurement result to the nearest 0.001 in. [0.025 mm].
stents, a table or graph of inflation pressure versus expanded
diameter should be developed and included in the labeling. A
7.4 Strut and Bridge Thickness:
minimum of ten replicate devices should be measured at each 7.4.1 Measurement—Strut and bridge thicknesses of the
stent size at each labeled inflation pressure.The expanded stent
expanded stent may be measured by subtraction of measured
inside diameter at each inflation pressure, rounded to the inside and outside diameters, by direct measurement with
nearest 0.05 mm, should be the mean of all measurements specialized instrumentation, by scanning electron microscopy,
taken on all stents at that pressure. The inflation pressure by profile projection, or destructively by cutting, or flattening,
should be expressed in atmospheres. This attribute does not or both, a stent for access by standard micrometers. Since
apply to self-expanding stents. polishing or other manufacturing processes may change strut
and bridge thickness from that of raw material, measurements
7.1.4 Uniformity of Expansion—The uniformity of expan-
from other-than-finished product should be used judiciously.
sion refers to the difference between the largest and smallest
Strut and bridge thickness should be measured at the stent
diameter measurement on a single stent deployed to its labeled
mid-length and near each end, at two circumferential locations
diameter. Uniformity of expansion is not intended to charac-
at each axial location. If strut and bridge thicknesses are
terize deliberate deviations from cylindricity, such as tapered
systematically different by design, they should be measured
construction, end flares, antimigration barbs, and so forth.
and reported separately. Strut and bridge thickness should be
Measurements for the uniformity of expansion should be taken
reported in inches to the nearest 0.0005 in. [0.013 mm].
at three axial locations (mid-length and close to each end) at
each of two circumferential orientations at about 90° separa-
7.5 Percent Solid Area:
tion. The uniformity of expansion reflects both the deviation
7.5.1 Measurement—The reference area is the full cylindri-
from circularity of the stent cross section and unintended
cal side surface area for the stent expanded to the labeled
differences in diameter along the stent length.
diameter(π·outsidediameter·lengthatlabeleddiameter).The
solid area may be estimated by stereology or image analysis of
7.2
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