ASTM F2081-01
(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
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 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 were selected for this guide. Where those units are not SI units, or derivatives thereof, SI units are provided in parentheses.
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Designation:F2081–01
Standard Guide for
Characterization and Presentation of the Dimensional
Attributes of Vascular Stents
This standard is issued under the fixed designation F 2081; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope States as of the time of the original approval of this guide.
Since a primary purpose of this guide is to promote uniformity
1.1 This guide covers the identification of and recom-
of labeling to facilitate the selection of devices by clinical
mended measurement methods for those dimensional attributes
users, the units most preferred by users were selected for this
of vascular stents that are deemed relevant to successful
guide. Where those units are not SI units, or derivatives
clinical performance. The delivery system packaged with and
thereof, SI units are provided in parentheses.
labeled specifically for use during the placement of the stent is
also included within the scope of this guide.
2. Referenced Documents
1.2 This guide addresses only the dimensional characteris-
2.1 ISO Standards:
tics of stents. Material property and stent functional character-
ISO 10555-1, Sterile, Single-Use Intravascular Catheters,
istics are not addressed herein. All dimensional characteristics
General Requirements
described in this guide refer to in-vitro (“bench-top”) charac-
ISO 10555-4, Sterile, Single-Use Intravascular Catheters—
terization. Because of variable patient factors, for example,
Balloon Dilation Catheters
vessel compliance, the actual in-vivo characteristics may be
slightly different.
3. Terminology
1.3 This guide includes recommendations generally appli-
3.1 Definitions of Terms Specific to This Standard:
cable to balloon-expandable and self-expanding stents fabri-
3.1.1 balloon-expandable stent, n—a stent that is expanded
cated from metals and metal alloys. It does not specifically
at the treatment site by a balloon catheter. The stent is altered
address any attributes unique to coated stents or polymeric or
permanently by the balloon expansion such that the stent
biodegradable stents, although the application of this guide to
remains expanded after deflation of the balloon.
those products is not precluded.
3.1.2 bridge, n—a connecting element between the radial
1.4 Whiletheyarenotspecificallyincludedwithinthescope
support aspects of a stent. A bridge may have unique design
of this guide, stents indicated for placement in nonvascular
features, as compared to a strut, to enhance longitudinal
locations, such as the esophagus or bile duct, also might be
flexibility and minimize shortening.
characterized by the methods contained herein. Likewise, this
3.1.3 crimp, v—tosecurethestentonthedeliverysystemby
guide does not include recommendations for endovascular
compressing the stent onto the balloon. Stents sold unmounted
grafts (“stent-grafts”) or other conduit devices commonly used
must be crimped manually by the clinical staff before use.
to treat aneurysmal disease or peripheral vessel trauma or to
3.1.4 crossing profile, n—a linear measure of the maximum
provide vascular access, although some information included
breadth of the stent/delivery system over the distal-most region
herein may be applicable to those devices.
of the delivery system.
1.5 This guide does not include recommendations for bal-
3.1.5 delivery system, n—a system that is used to deliver
loon catheters sold as stand-alone angioplasty catheters, even
and deploy a stent at the target site. A delivery system may be
though some of those catheters may be used for the delivery of
similar to a balloon dilatation catheter; a delivery system for a
unmounted stents supplied without a delivery system. Require-
self-expanding stent might not have a balloon.
ments for angioplasty catheters are contained in standards ISO
3.1.6 diameter, n—referstotheoutsidediameterofthestent
10555-1 and ISO 10555-4.
unless otherwise noted.
1.6 The units of measurements used throughout this guide
3.1.7 percent metal area, n—that percentage of the pro-
reflect the hybrid system in common clinical use in the United
jected cylindrical side surface area (p times outside diameter
This guide is under the jurisdiction of ASTM Committee F04 on Medical and
Surgical Materials and Devicesand is the direct responsibility of Subcommittee
F04.30on Cardiovascular Devices. Available from American National Standards Institute, 11 W. 42nd St., 13th
Current edition approved Jan. 10, 2001. Published April 2001. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F2081
times length at labeled diameter) that is covered by stent 5.1.1 Mounting—Premounted or unmounted.
material, when the stent is expanded to its labeled diameter. 5.1.2 Expansion—Balloon expandable or self-expanding.
3.1.8 premounted stent, n—a stent supplied by a manufac-
6. Test Devices and General Procedures
turer already mounted on a delivery system.
6.1 Unless otherwise justified, all samples selected for
3.1.9 self-expanding stent, n—a stent that expands without
testing or measuring the attributes described in this guide
extrinsic force or pressure, to a size and shape close to the
should be taken from finished, clinical-quality product. Cos-
desired final size and shape, when released from the delivery
metic rejects or other nonclinical samples may be used if the
system. The self-expanding nature of some stents is a design
cause for rejection is not related to the attribute being assessed.
feature resulting from the materials of construction or the
Sterilization can be omitted if it can be demonstrated that
structural geometry, or both.
sterilization has no affect on the attribute being assessed.
3.1.10 sheath, n—a movable cover that constrains a self-
6.2 When specimen preparation (for example, manual
expanding stent on the delivery system until its desired release
crimping onto a delivery system, balloon expansion), is re-
or protects a balloon-expandable stent during delivery before
quired before testing, this should be done in accordance with
deployment.
the Instructions for Use (IFU).
3.1.11 shortening/lengthening, n—the percentage change in
length between the undeployed mounted condition and the 6.3 The preconditioning and test environments must be
appropriately selected for each design and attribute. Tempera-
expanded labeled-diameter condition.
3.1.12 stent, vascular, n—a synthetic tubular structure that ture and fluid immersion may have a significant effect on some
attributes but a negligible affect on others. For example, fluid
is permanently implanted in the native or grafted vasculature
and that is intended to provide mechanical radial support to sorption may swell catheters and affect the measurement of
crossing profile. Temperature may affect the final deployed
enhance vessel patency. For the purposes of this guide, a stent
is metallic and not covered by synthetic textile or tissue graft diameter for stents made from shape memory materials. For
measurementsforwhichdeployment,ormeasurement,orboth,
material.
is to be made in a controlled environment, the stent or delivery
3.1.13 strut, n—thesmallestindividualelementoftheradial
system, or both, should be immersed in a water bath main-
support aspect of a stent that has a solid cross section in both
tained at 37 6 2°C and allowed to equilibrate.
the radial and circumferential directions.
6.4 The number of specimens evaluated for each diameter
3.1.14 unmounted stent, n—a stent that is not crimped on a
for each stent design should be sufficient to meet the sampling
delivery system as supplied by the manufacturer. Before use,
requirementsforthedesiredlabeling.Ingeneral,aminimumof
the clinical staff must manually crimp unmounted stents onto a
ten test devices is recommended. If a single stent design is
delivery device.
intendedtobedeployedoverabroadrangeofdiametersbyuse
4. Significance and Use
on different size delivery systems, the dimensional attributes
4.1 Vascular stents are intended for permanent implant in should be evaluated for each stent/delivery system combina-
the human vasculature (native or graft) for the purposes of tion.
maintaining vessel patency. The dimensional attributes of
7. Dimensions and Measurement Methods
vascular stents are critical parameters that aid clinicians in the
7.1 Deployed Diameter—Unless otherwise specified, all
selection of devices for individual patients.This guide contains
deployed diameters refer to the outside diameter, reported in
a listing of those attributes that are directly related to the
millimetres to the nearest 0.1 mm, after balloon deflation (for
clinical utility and performance of these devices, along with
balloon-expandable stents).
recommendations for consistent methods of measuring these
7.1.1 Measurement—The outside diameter of deployed
attributes and presenting the information for use in clinical
stents should be measured by noncontacting instruments (pro-
decision making. This guide can be used by the manufacturers
and researchers of stents to provide consistency of measure- fileprojection,lasermicrometer,andsoforth)witharesolution
of 0.05 mm or better.
ment and labeling of these dimensional characteristics. It may
have use in the regulation of these devices by appropriate 7.1.2 Labeled Diameter—The labeled diameter is that typi-
cally used to identify the nominal deployed size of a particular
authorities.
device, for example, 3 mm, 3.5 mm, and must be clearly
4.2 The dimensional attributes included in this guide are
identified as inside or outside diameter (ID or OD).
those that are deemed related to or possibly predictive of
7.1.3 Stent System Compliance—For balloon-expandable
successful clinical performance of the stent, based on prior
stents, a table or graph of inflation pressure versus expanded
clinicalexperience;however,becauseofthemyriadpatientand
diameter should be developed and included in the labeling. A
medical factors that influence the clinical outcome of any
minimum of ten devices should be measured at each labeled
individual treatment, conformance of a stent and de
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