ASTM F2394-07(2017)

Standard Guide for Measuring Securement of Balloon Expandable Vascular Stent Mounted on Delivery System

SIGNIFICANCE AND USE
4.1 The securement of the endovascular stent on the balloon is a critical parameter to ensure that the stent is safely delivered to or from the treatment site.  
4.2 This guide is intended for use by researchers and manufacturers for the development and selection of pre-test treatments, tests and test endpoints to measure stent securement (displacement distances and dislodgment forces).  
4.3 This guide may be used to investigate which practical combinations of in vitro tests best characterize clinical scenarios.  
4.4 This guide should be used with discretion in choosing securement tests and evaluating results due to the myriad possible combinations of clinical conditions, failure modes, and stent delivery system designs.  
4.5 This guide may be of use for developing a test for meeting parts 2 and 3 of the requirements of EN 14299, Section 7.3.4.4 on Trackability.  
4.6 This guide may be of use for developing a test to meet section VII-C-8 of CDRH Guidance document.
SCOPE
1.1 This guide provides guidance for the design and development of pre-test treatments, tests, and test endpoints to measure stent securement of pre-mounted, unsheathed, balloon-expandable stent delivery systems. This guide is intended to aid investigators in the design, development, and in vitro characterization of pre-mounted, unsheathed, balloon-expandable stent delivery systems.  
1.2 This guide covers the laboratory determination of the shear force required to displace or dislodge a balloon-expandable endovascular stent mounted on a delivery system. The guide proposes a set of options to consider when testing stent securement. The options cover pre-test treatments, possible stent securement tests, and relevant test endpoints. An example test apparatus is given in 7.1.  
1.3 This guide covers in vitro bench testing characterization only. Measured levels of securement and product design/process differentiation may be particularly influenced by selections of pre-test treatments, securement test type (for example, stent gripping method), and test endpoint. In vivo characteristics may also differ from in vitro results.  
1.4 This guide does not cover all possible pre-test treatments, stent securement tests, or test endpoints. It is intended to provide a starting point from which to select and investigate securement test options.  
1.5 This guide does not specify a method for mounting the stent onto the delivery system.  
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.  
1.7 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 and health practices and determine the applicability of regulatory requirements 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: Historical
• Publication Date: 31-Aug-2017
• ICS: 11.040.20 - Transfusion, infusion and injection equipment
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.30 - Cardiovascular Standards

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F2394 − 07 (Reapproved 2017)
Standard Guide for
Measuring Securement of Balloon Expandable Vascular
Stent Mounted on Delivery System
This standard is issued under the fixed designation F2394; 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 1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This guide provides guidance for the design and devel-
responsibility of the user of this standard to establish appro-
opment of pre-test treatments, tests, and test endpoints to
priate safety and health practices and determine the applica-
measure stent securement of pre-mounted, unsheathed,
bility of regulatory requirements prior to use.
balloon-expandable stent delivery systems. This guide is in-
1.8 This international standard was developed in accor-
tended to aid investigators in the design, development, and in
dance with internationally recognized principles on standard-
vitro characterization of pre-mounted, unsheathed, balloon-
ization established in the Decision on Principles for the
expandable stent delivery systems.
Development of International Standards, Guides and Recom-
1.2 This guide covers the laboratory determination of the
mendations issued by the World Trade Organization Technical
shear force required to displace or dislodge a balloon-
Barriers to Trade (TBT) Committee.
expandable endovascular stent mounted on a delivery system.
The guide proposes a set of options to consider when testing
2. Referenced Documents
stent securement. The options cover pre-test treatments, pos- 2
2.1 ASTM Standards:
sible stent securement tests, and relevant test endpoints. An
E1169 Practice for Conducting Ruggedness Tests
example test apparatus is given in 7.1.
E1488 GuideforStatisticalProcedurestoUseinDeveloping
1.3 This guide covers in vitro bench testing characterization and Applying Test Methods
only. Measured levels of securement and product design/
2.2 Other Documents:
process differentiation may be particularly influenced by selec-
ISO 10555-1 Sterile Sterile Sterile, Single-use Intravascular
tions of pre-test treatments, securement test type (for example,
Catheters—Part 1: General Requirements
stent gripping method), and test endpoint. In vivo characteris-
Quality System Regulation, Part VII Dept. Health and Hu-
tics may also differ from in vitro results.
man Services, Food and Drug Administration, 21 CFR
Part 820 Medical Devices; Current Good Manufacturing
1.4 This guide does not cover all possible pre-test
Practice; Final Rule. Federal Register, October 7, 1996
treatments, stent securement tests, or test endpoints. It is
EN 14299 Non Active Surgical Implants—Particular Re-
intended to provide a starting point from which to select and
quirements for Cardiac and Vascular Implants—Specific
investigate securement test options.
Requirements For Arterial Stents, May 2004
1.5 This guide does not specify a method for mounting the
CDRH Guidance, Non-Clinical Tests and Recommended
stent onto the delivery system.
Labeling for Intravascular Stents andAssociated Delivery
Systems, January 13, 2005
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
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
system shall be used independently of the other. Combining
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
values from the two systems may result in non-conformance
Standards volume information, refer to the standard’s Document Summary page on
with the standard.
the ASTM website.
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org.
AvailablefromU.S.GovernmentPrintingOfficeSuperintendentofDocuments,
This guide is under the jurisdiction of ASTM Committee F04 on Medical and 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
Surgical Materials and Devices and is the direct responsibility of Subcommittee www.access.gpo.gov.
F04.30 on Cardiovascular Standards. Available from British Standards Institute (BSI), 389 Chiswick High Rd.,
Current edition approved Sept. 1, 2017. Published September 2017. Originally London W4 4AL, U.K., http://www.bsi-global.com.
approved in 2004. Last previous edition approved in 2013 as F2394 – 07 (2013). Available from Food and Drug Administration (FDA), 5600 Fishers Ln.,
DOI: 10.1520/F2394-07R17. Rockville, MD 20857,. Http://www.fda.gov/cdrh/ode/guidance/1545.pdf.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2394 − 07 (2017)
MAUDE Database makes the contact with the stent. Typical grips used to apply
force to the stent include shims (as used in Figs. X2.5-X2.8);
3. Terminology
tape which sticks to the stent but not the balloon; an iris which
can be narrowed down to allow the balloon to slip by but not
3.1 Definitions:
the stent; or nubs which contact the stent but not the balloon.
3.1.1 balloon expandable stent, n—a stent that is expanded
at the treatment site by a balloon catheter. The stent material is
3.1.12 guide catheter, n—a tube designed to transport the
plastically deformed by the balloon expansion such that the
guide-wire and the stent delivery system into the target vessel.
stent remains expanded after deflation of the balloon.
3.1.13 guide-wire, n—a wire designed to aid in balloon,
3.1.2 crimp, v—tosecurethestentonthedeliverysystemby
ultrasound, atherectomy, or stent placement during endovascu-
radially compressing and plastically deforming the stent onto
lar procedures.
the balloon.
3.1.14 mandrel, n—awirethatmaybeusedasanalternative
3.1.3 delivery system, n—a system similar to a balloon
to the intended guide-wire to provide support for the catheter
dilatation catheter that is used to deliver and deploy a stent at
guide-wire lumen for some test procedures.
the target site and then removed.
3.1.15 non-recoverable movement, n—a displacement of the
3.1.4 displacement force, critical distance peak, n—a stent
stent relative to the balloon such that if the shearing force was
securement test endpoint characterizing the maximum force
reduced to zero, the stent would remain displaced in the
required to displace the stent with respect to the balloon a
direction of the shearing force relative to the initial placement
critical distance. This critical distance is the minimum of the
on the balloon. The force at which non-recoverable movement
following two distances. The first is the distance at which the
begins is defined as the initial displacement force (see defini-
undamaged stent could overhang the balloon body resulting in
tion above).
a clinically significant, incomplete end deployment. The sec-
3.1.16 pre-test treatment, n—a treatment of the stent deliv-
ond is the length (distance) of stent compression or buckling
ery system prior to the evaluation of securement that simulates
that could result in a clinically significant incomplete deploy-
preparatory, environmental, mechanical or other conditions
ment of the stent against the vessel walls. (See Fig. X2.1.)
that may be encountered prior to or during clinical use of the
3.1.5 displacement force, initial, n—a stent securement test
device. Examples include subjecting the devices to elevated
endpointcharacterizingtheinitialforcerequiredtodisplacethe
shipping temperature/humidity, catheter preparation per use
stent with respect to the balloon such that the displacement is
instructions, pre-soaking, bending treatments, tracking treat-
a non-recoverable movement (see 3.1.15). (See Fig. X2.1.)
ments (tracking fixture, see definition below) and tracking
3.1.6 displacement force, initial peak, n—astentsecurement
through lesion treatments (lesion fixture, see definition below).
test endpoint characterizing the first peak in force that occurs
3.1.17 pre-test treatment tracking fixture, n—apre-testtreat-
during or after stent displacement with respect to the balloon.
mentfixtureusedtosimulateananatomicalvasculature.Useof
(See Fig. X2.1.)
the fixture with a guide catheter, a guide-wire and the stent-
3.1.7 dislodgment force, peak, n—a stent securement test
balloon catheter delivery system is intended to simulate the
endpointcharacterizingthepeakormaximumforcerequiredto
bending and frictional forces of tracking the device to the
completelydislodgethestentfromthedeliverysystemballoon.
lesion site that may be encountered in the clinical setting. See
During a test, this force will occur after or coincide with the
the engineering diagrams in the Appendix. Note that these
initial displacement force. (See Fig. X2.1.)
engineering diagrams simulate vessels with a moderately
3.1.8 end flaring, n—a distal or proximal outward conical difficult degree of coronary tortuousity but do not include
opening of the diameter of the stent on the balloon. End flaring
simulated lesions.
is a contributing factor to the probability that the stent may
3.1.18 pre-test treatment lesion fixture, n—a pre-test treat-
become caught during withdrawal into a guide catheter while
ment fixture used to simulate an anatomical vasculature and
tracking through a lesion.
lesion. Use of the fixture with a guide catheter, a guide-wire,
3.1.9 failure mode effect analysis (FMEA), n—an analytical
and the stent-balloon catheter delivery system is intended to
approach to methodically determine and address all possible
simulate the bending, frictional and mechanical resistance
product failure modes, their associated causes, and their
forces of tracking the device across the lesion site that may be
criticality. Used to evaluate designs, prioritize testing, and
encountered in the clinical setting.
track risk reducing improvements to the product.
3.1.19 securement test, guide-type, n—a stent securement
3.1.10 gauge length, n—the initial unstressed length of
test that is similar to the clinical scenario of pulling an
catheter tubing between the proximal end of the stent to the
undeployed stent delivery system back into a guide catheter,
grips which engage the catheter tubing.
arterial sheath or hemostasis valve. Examples include guides,
3.1.11 grips, n—a means of applying force to the stent and rings,orshimsideallydesignedtoengagethestentendorbody
balloon catheter to displace or dislodge the stent relative to the but not the catheter balloon. The shim securement test, de-
balloon. In particular, grips refer to the end of a device which scribedinSection7,usescomplementarythin,rigidplateswith
rounded “V” notches that are sized to circumferentially engage
the stent end but not the catheter balloon. See the engineering
Http://www.fda.gov/cdrh/maude.html. diagrams in the Appendix.
F2394 − 07 (2017)
3.1.20 securement test, lesion-type, n—a stent securement 6. Test Method Considerations
test that is similar to the clinical scenario of pushing or pulling
6.1 Flowchart—See Fig. 1.
an undeployed stent delivery system through or around a
6.2 Development and Evaluation of Securement Tests:
fibrous or calcified lesion. Examples include tape, nubs,
protrusions or sandpaper ideally designed to engage the stent
6.2.1 Securement test development and selection is ideally
end or body but not the catheter balloon. begun through the initial use of a battery of tests measuring a
variety of failure modes. These test methods may vary from a
4. Significance and Use simple intuitive tactile impression of the securement forces
through manipulation to clinically modeled situations with
4.1 The securement of the endovascular stent on the balloon
guide catheters and stenosis models to in vivo animal studies
isacriticalparametertoensurethatthestentissafelydelivered
with representative anatomy and physician handling. From a
to or from the treatment site.
safety-risk perspective, consider how securement challenges
may occur in clinical situations, what may result from loss of
4.2 This guide is intended for use by researchers and
securement, what the severity of the outcome is to the patient,
manufacturers for the development and selection of pre-test
what the frequency of these situations are, and then how to test
treatments, tests and test endpoints to measure stent secure-
to detect these occurrences. Factors to consider in evaluating
ment (displacement distances and dislodgment forces).
securement tests include the following:
4.3 This guide may be used to investigate which practical
6.2.1.1 Review of the MAUDE database for reported prob-
combinations of in vitro tests best characterize clinical sce-
lems with comparable devices.
narios.
6.2.1.2 Physician surveys for clinical relevance and prob-
lems with comparable devices.
4.4 This guide should be used with discretion in choosing
securement tests and evaluating results due to the myriad 6.2.1.3 Mechanical understanding of the tests’ clinical rel-
evance and limitations.
possible combinations of clinical conditions, failure modes,
and stent delivery system designs.
6.2.1.4 Mechanical and statistical understanding of the test
reproducibility limitations due to device variation, pre-test
4.5 This guide may be of use for developing a test for
treatments, various grips, and test conditions.
meeting parts 2 and 3 of the requirements of EN 14299,
6.2.1.5 Ability to set accept/reject criteria by physician
Section 7.3.4.4 on Trackability.
evaluation, by historical comparisons, or by other rational
4.6 This guide may be of use for developing a test to meet
means.
section VII-C-8 of CDRH Guidance document.
6.2.2 The final securement test(s) selected must ultimately
satisfy internal manufacturer quality standards. These stan-
5. Clinical Scenarios
dards may include clinical relevance, FMEA analysis, statisti-
cal assurance of characteristics, and challenge assurance of
5.1 There are two failure modes—the stent is dislodged
characteristics.
from the catheter or the stent is displaced or deformed on the
6.2.3 The final securement test(s) must also satisfy external
catheter such that balloon inflation delivery would not produce
regulatorybodystandards.Forexample,theFDAQSR21CFR
an acceptable stent shape at the proper location. Based on
Part 820, Oct. 7, 1996 states that each test used in the process
reported clinical incidents, there are three causes for these two
ofdesignandmanufacturingoffinisheddevices“issuitablefor
types of failures:
its intended purposes and is
...

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: F2394 − 07 (Reapproved 2013) F2394 − 07 (Reapproved 2017)
Standard Guide for
Measuring Securement of Balloon Expandable Vascular
Stent Mounted on Delivery System
This standard is issued under the fixed designation F2394; 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 This guide provides guidance for the design and development of pre-test treatments, tests, and test endpoints to measure
stent securement of pre-mounted, unsheathed, balloon-expandable stent delivery systems. This guide is intended to aid
investigators in the design, development, and in vitro characterization of pre-mounted, unsheathed, balloon-expandable stent
delivery systems.
1.2 This guide covers the laboratory determination of the shear force required to displace or dislodge a balloon-expandable
endovascular stent mounted on a delivery system. The guide proposes a set of options to consider when testing stent securement.
The options cover pre-test treatments, possible stent securement tests, and relevant test endpoints. An example test apparatus is
given in 7.1.
1.3 This guide covers in vitro bench testing characterization only. Measured levels of securement and product design/process
differentiation may be particularly influenced by selections of pre-test treatments, securement test type (for example, stent gripping
method), and test endpoint. In vivo characteristics may also differ from in vitro results.
1.4 This guide does not cover all possible pre-test treatments, stent securement tests, or test endpoints. It is intended to provide
a starting point from which to select and investigate securement test options.
1.5 This guide does not specify a method for mounting the stent onto the delivery system.
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.
1.7 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 and health practices and determine the applicability of regulatory
requirements 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.
2. Referenced Documents
2.1 ASTM Standards:
E1169 Practice for Conducting Ruggedness Tests
E1488 Guide for Statistical Procedures to Use in Developing and Applying Test Methods
2.2 Other Documents:
ISO 10555-1 Sterile Sterile Sterile, Single-use Intravascular Catheters—Part 1: General Requirements
This guide is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee F04.30
on Cardiovascular Standards.
Current edition approved March 1, 2013Sept. 1, 2017. Published March 2013September 2017. Originally approved in 2004. Last previous edition approved in 20072013
as F2394 – 07.F2394 – 07 (2013). DOI: 10.1520/F2394-07R13.10.1520/F2394-07R17.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2394 − 07 (2017)
Quality System Regulation, Part VII Dept. Health and Human Services, Food and Drug Administration, 21 CFR Part 820
Medical Devices; Current Good Manufacturing Practice; Final Rule. Federal Register, October 7, 1996
EN 14299 Non Active Surgical Implants—Particular Requirements for Cardiac and Vascular Implants—Specific Requirements
For Arterial Stents, May 2004
CDRH Guidance, Non-Clinical Tests and Recommended Labeling for Intravascular Stents and Associated Delivery Systems,
January 13, 2005
MAUDE Database
3. Terminology
3.1 Definitions:
3.1.1 balloon expandable stent, n—a stent that is expanded at the treatment site by a balloon catheter. The stent material is
plastically deformed by the balloon expansion such that the stent remains expanded after deflation of the balloon.
3.1.2 crimp, v—to secure the stent on the delivery system by radially compressing and plastically deforming the stent onto the
balloon.
3.1.3 delivery system, n—a system similar to a balloon dilatation catheter that is used to deliver and deploy a stent at the target
site and then removed.
3.1.4 displacement force, critical distance peak, n—a stent securement test endpoint characterizing the maximum force required
to displace the stent with respect to the balloon a critical distance. This critical distance is the minimum of the following two
distances. The first is the distance at which the undamaged stent could overhang the balloon body resulting in a clinically
significant, incomplete end deployment. The second is the length (distance) of stent compression or buckling that could result in
a clinically significant incomplete deployment of the stent against the vessel walls. (See Fig. X2.1.)
3.1.5 displacement force, initial, n—a stent securement test endpoint characterizing the initial force required to displace the stent
with respect to the balloon such that the displacement is a non-recoverable movement (see 3.1.15). (See Fig. X2.1.)
3.1.6 displacement force, initial peak, n—a stent securement test endpoint characterizing the first peak in force that occurs
during or after stent displacement with respect to the balloon. (See Fig. X2.1.)
3.1.7 dislodgment force, peak, n—a stent securement test endpoint characterizing the peak or maximum force required to
completely dislodge the stent from the delivery system balloon. During a test, this force will occur after or coincide with the initial
displacement force. (See Fig. X2.1.)
3.1.8 end flaring, n—a distal or proximal outward conical opening of the diameter of the stent on the balloon. End flaring is a
contributing factor to the probability that the stent may become caught during withdrawal into a guide catheter while tracking
through a lesion.
3.1.9 failure mode effect analysis (FMEA), n—an analytical approach to methodically determine and address all possible product
failure modes, their associated causes, and their criticality. Used to evaluate designs, prioritize testing, and track risk reducing
improvements to the product.
3.1.10 gauge length, n—the initial unstressed length of catheter tubing between the proximal end of the stent to the grips which
engage the catheter tubing.
3.1.11 grips, n—a means of applying force to the stent and balloon catheter to displace or dislodge the stent relative to the
balloon. In particular, grips refer to the end of a device which makes the contact with the stent. Typical grips used to apply force
to the stent include shims (as used in Figs. X2.5-X2.8); tape which sticks to the stent but not the balloon; an iris which can be
narrowed down to allow the balloon to slip by but not the stent; or nubs which contact the stent but not the balloon.
3.1.12 guide catheter, n—a tube designed to transport the guide-wire and the stent delivery system into the target vessel.
3.1.13 guide-wire, n—a wire designed to aid in balloon, ultrasound, atherectomy, or stent placement during endovascular
procedures.
3.1.14 mandrel, n—a wire that may be used as an alternative to the intended guide-wire to provide support for the catheter
guide-wire lumen for some test procedures.
3.1.15 non-recoverable movement, n—a displacement of the stent relative to the balloon such that if the shearing force was
reduced to zero, the stent would remain displaced in the direction of the shearing force relative to the initial placement on the
balloon. The force at which non-recoverable movement begins is defined as the initial displacement force (see definition above).
Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
www.access.gpo.gov.
Available from British Standards Institute (BSI), 389 Chiswick High Rd., London W4 4AL, U.K., http://www.bsi-global.com.
Available from Food and Drug Administration (FDA), 5600 Fishers Ln., Rockville, MD 20857,. Http://www.fda.gov/cdrh/ode/guidance/1545.pdf.
Http://www.fda.gov/cdrh/maude.html.
F2394 − 07 (2017)
3.1.16 pre-test treatment, n—a treatment of the stent delivery system prior to the evaluation of securement that simulates
preparatory, environmental, mechanical or other conditions that may be encountered prior to or during clinical use of the device.
Examples include subjecting the devices to elevated shipping temperature/humidity, catheter preparation per use instructions,
pre-soaking, bending treatments, tracking treatments (tracking fixture, see definition below) and tracking through lesion treatments
(lesion fixture, see definition below).
3.1.17 pre-test treatment tracking fixture, n—a pre-test treatment fixture used to simulate an anatomical vasculature. Use of the
fixture with a guide catheter, a guide-wire and the stent-balloon catheter delivery system is intended to simulate the bending and
frictional forces of tracking the device to the lesion site that may be encountered in the clinical setting. See the engineering
diagrams in the Appendix. Note that these engineering diagrams simulate vessels with a moderately difficult degree of coronary
tortuousity but do not include simulated lesions.
3.1.18 pre-test treatment lesion fixture, n—a pre-test treatment fixture used to simulate an anatomical vasculature and lesion. Use
of the fixture with a guide catheter, a guide-wire, and the stent-balloon catheter delivery system is intended to simulate the bending,
frictional and mechanical resistance forces of tracking the device across the lesion site that may be encountered in the clinical
setting.
3.1.19 securement test, guide-type, n—a stent securement test that is similar to the clinical scenario of pulling an undeployed
stent delivery system back into a guide catheter, arterial sheath or hemostasis valve. Examples include guides, rings, or shims
ideally designed to engage the stent end or body but not the catheter balloon. The shim securement test, described in Section 7,
uses complementary thin, rigid plates with rounded “V” notches that are sized to circumferentially engage the stent end but not
the catheter balloon. See the engineering diagrams in the Appendix.
3.1.20 securement test, lesion-type, n—a stent securement test that is similar to the clinical scenario of pushing or pulling an
undeployed stent delivery system through or around a fibrous or calcified lesion. Examples include tape, nubs, protrusions or
sandpaper ideally designed to engage the stent end or body but not the catheter balloon.
4. Significance and Use
4.1 The securement of the endovascular stent on the balloon is a critical parameter to ensure that the stent is safely delivered
to or from the treatment site.
4.2 This guide is intended for use by researchers and manufacturers for the development and selection of pre-test treatments,
tests and test endpoints to measure stent securement (displacement distances and dislodgment forces).
4.3 This guide may be used to investigate which practical combinations of in vitro tests best characterize clinical scenarios.
4.4 This guide should be used with discretion in choosing securement tests and evaluating results due to the myriad possible
combinations of clinical conditions, failure modes, and stent delivery system designs.
4.5 This guide may be of use for developing a test for meeting parts 2 and 3 of the requirements of EN 14299, Section 7.3.4.4
on Trackability.
4.6 This guide may be of use for developing a test to meet section VII-C-8 of CDRH Guidance document.
5. Clinical Scenarios
5.1 There are two failure modes—the stent is dislodged from the catheter or the stent is displaced or deformed on the catheter
such that balloon inflation delivery would not produce an acceptable stent shape at the proper location. Based on reported clinical
incidents, there are three causes for these two types of failures:
5.1.1 Displacement or dislodgment of the stent while attempting to track through or position in tortuous bends, fibrous or
calcified lesions, or previously implanted stents, or combination thereof.
5.1.2 Displacement or dislodgment of the stent on withdrawal of the undeployed stent delivery system back into the guide
catheter, introducer sheath, or hemostasis valve. This failure type is usually associated with failure to cross tortuous bends, fibrous
or calcified lesions, or previously implanted stents, or combination thereof. It is sometimes associated with less-than-ideal seating
or angled placement of the guide catheter tip in the ostium of the vessel.
5.1.3 Displacement or dislodgement of the stent due to improper catheter preparation including mishandling or partial balloon
inflation during preparation. This has been identified in a few cases where the loose, displaced, or dislodged stent was observed
prior to use but may conceivably play a role in a small percentage of cases where dislodgment occurs in patients.
6. Test Method Considerations
6.1 Flowchart—See Fig. 1.
6.2 Development and Evaluation of Securement Tests:
6.2.1 Securement test development and selection is ideally begun through the initial use of a battery of tests measuring a variety
of failure modes. These test methods may vary from a simple intuitive tactile impression of the securement forces through
manipulation to clinically modeled situations with guide catheters and stenosis models to in vivo animal studies with representative
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