Designation: F2394 – 07

Standard Guide for

Measuring Securement of Balloon Expandable Vascular
Stent Mounted on Delivery System1
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 2. Referenced Documents

1.1 This guide provides guidance for the design and devel- 2.1 ASTM Standards:2
opment of pre-test treatments, tests, and test endpoints to E1169 Practice for Conducting Ruggedness Tests
measure stent securement of pre-mounted, unsheathed, E1488 Guide for Statistical Procedures to Use in Develop-
balloon-expandable stent delivery systems. This guide is in- ing and Applying Test Methods
tended to aid investigators in the design, development, and in 2.2 Other Documents:
vitro characterization of pre-mounted, unsheathed, balloon- ISO 10555-1 Sterile Sterile Sterile, Single-use Intravascular
expandable stent delivery systems. Catheters—Part 1: General Requirements3
1.2 This guide covers the laboratory determination of the Quality System Regulation, Part VII Dept. Health and
shear force required to displace or dislodge a balloon- Human Services, Food and Drug Administration, 21 CFR
expandable endovascular stent mounted on a delivery system. Part 820 Medical Devices; Current Good Manufacturing
The guide proposes a set of options to consider when testing Practice; Final Rule. Federal Register, October 7, 19964
stent securement. The options cover pre-test treatments, pos- EN 14299 Non Active Surgical Implants—Particular Re-
sible stent securement tests, and relevant test endpoints. An quirements for Cardiac and Vascular Implants—Specific
example test apparatus is given in 7.1. Requirements For Arterial Stents, May 20045
1.3 This guide covers in vitro bench testing characterization CDRH Guidance, Non-Clinical Tests and Recommended
only. Measured levels of securement and product design/ Labeling for Intravascular Stents and Associated Delivery
process differentiation may be particularly influenced by selec- Systems, January 13, 20056
tions of pre-test treatments, securement test type (for example, MAUDE Database7
stent gripping method), and test endpoint. In vivo characteris-
tics may also differ from in vitro results. 3. Terminology
1.4 This guide does not cover all possible pre-test treat- 3.1 Definitions:
ments, stent securement tests, or test endpoints. It is intended to 3.1.1 balloon expandable stent, n—a stent that is expanded
provide a starting point from which to select and investigate at the treatment site by a balloon catheter. The stent material is
securement test options. plastically deformed by the balloon expansion such that the
1.5 This guide does not specify a method for mounting the stent remains expanded after deflation of the balloon.
stent onto the delivery system.
1.6 This standard does not purport to address all of the 2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
safety concerns, if any, associated with its use. It is the contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
responsibility of the user of this standard to establish appro- Standards volume information, refer to the standard’s Document Summary page on
priate safety and health practices and determine the applica- the ASTM website.
3
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
bility of regulatory requirements prior to use. 4th Floor, New York, NY 10036, http://www.ansi.org.
4
Available from U.S. Government Printing Office Superintendent of Documents,
732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
1
This guide is under the jurisdiction of ASTM Committee F04 on Medical and www.access.gpo.gov.
5
Surgical Materials and Devices and is the direct responsibility of Subcommittee Available from British Standards Institute (BSI), 389 Chiswick High Rd.,
F04.30 on Cardiovascular Standards. London W4 4AL, U.K., http://www.bsi-global.com.
6
Current edition approved July 15, 2007. Published August 2007. Originally Available from Food and Drug Administration (FDA), 5600 Fishers Ln.,
approved in 2004. Last previous edition approved in 2004 as F2394 – 04. DOI: Rockville, MD 20857,. Http://www.fda.gov/cdrh/ode/guidance/1545.pdf.
7
10.1520/F2394-07. Http://www.fda.gov/cdrh/maude.html.

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3.1.2 crimp, v—to secure the stent on the delivery system by 3.1.15 non-recoverable movement, n—a displacement of the
radially compressing and plastically deforming the stent onto stent relative to the balloon such that if the shearing force was
the balloon. reduced to zero, the stent would remain displaced in the
3.1.3 delivery system, n—a system similar to a balloon direction of the shearing force relative to the initial placement
dilatation catheter that is used to deliver and deploy a stent at on the balloon. The force at which non-recoverable movement
the target site and then removed. begins is defined as the initial displacement force (see defini-
3.1.4 displacement force, critical distance peak, n—a stent tion above).
securement test endpoint characterizing the maximum force 3.1.16 pre-test treatment, n—a treatment of the stent deliv-
required to displace the stent with respect to the balloon a ery system prior to the evaluation of securement that simulates
critical distance. This critical distance is the minimum of the preparatory, environmental, mechanical or other conditions
following two distances. The first is the distance at which the that may be encountered prior to or during clinical use of the
undamaged stent could overhang the balloon body resulting in device. Examples include subjecting the devices to elevated
a clinically significant, incomplete end deployment. The sec- shipping temperature/humidity, catheter preparation per use
ond is the length (distance) of stent compression or buckling instructions, pre-soaking, bending treatments, tracking treat-
that could result in a clinically significant incomplete deploy- ments (tracking fixture, see definition below) and tracking
ment of the stent against the vessel walls. (See Fig. X2.1.) through lesion treatments (lesion fixture, see definition below).
3.1.5 displacement force, initial, n—a stent securement test 3.1.17 pre-test treatment tracking fixture, n—a pre-test
endpoint characterizing the initial force required to displace the treatment fixture used to simulate an anatomical vasculature.
stent with respect to the balloon such that the displacement is Use of the fixture with a guide catheter, a guide-wire and the
a non-recoverable movement (see 3.1.15). (See Fig. X2.1.) stent-balloon catheter delivery system is intended to simulate
3.1.6 displacement force, initial peak, n—a stent secure- the bending and frictional forces of tracking the device to the
ment test endpoint characterizing the first peak in force that lesion site that may be encountered in the clinical setting. See
occurs during or after stent displacement with respect to the the engineering diagrams in the Appendix. Note that these
balloon. (See Fig. X2.1.) engineering diagrams simulate vessels with a moderately
3.1.7 dislodgment force, peak, n—a stent securement test difficult degree of coronary tortuousity but do not include
endpoint characterizing the peak or maximum force required to simulated lesions.
completely dislodge the stent from the delivery system balloon. 3.1.18 pre-test treatment lesion fixture, n—a pre-test treat-
During a test, this force will occur after or coincide with the ment fixture used to simulate an anatomical vasculature and
initial displacement force. (See Fig. X2.1.) lesion. Use of the fixture with a guide catheter, a guide-wire,
3.1.8 end flaring, n—a distal or proximal outward conical and the stent-balloon catheter delivery system is intended to
opening of the diameter of the stent on the balloon. End flaring simulate the bending, frictional and mechanical resistance
is a contributing factor to the probability that the stent may forces of tracking the device across the lesion site that may be
become caught during withdrawal into a guide catheter while encountered in the clinical setting.
tracking through a lesion. 3.1.19 securement test, guide-type, n—a stent securement
3.1.9 failure mode effect analysis (FMEA), n—an analytical test that is similar to the clinical scenario of pulling an
approach to methodically determine and address all possible undeployed stent delivery system back into a guide catheter,
product failure modes, their associated causes, and their arterial sheath or hemostasis valve. Examples include guides,
criticality. Used to evaluate designs, prioritize testing, and rings, or shims ideally designed to engage the stent end or body
track risk reducing improvements to the product. but not the catheter balloon. The shim securement test, de-
3.1.10 gauge length, n—the initial unstressed length of scribed in Section 7, uses complementary thin, rigid plates with
catheter tubing between the proximal end of the stent to the rounded “V” notches that are sized to circumferentially engage
grips which engage the catheter tubing. the stent end but not the catheter balloon. See the engineering
3.1.11 grips, n—a means of applying force to the stent and diagrams in the Appendix.
balloon catheter to displace or dislodge the stent relative to the 3.1.20 securement test, lesion-type, n—a stent securement
balloon. In particular, grips refer to the end of a device which test that is similar to the clinical scenario of pushing or pulling
makes the contact with the stent. Typical grips used to apply an undeployed stent delivery system through or around a
force to the stent include shims (as used in Figs. X2.5-X2.8); fibrous or calcified lesion. Examples include tape, nubs,
tape which sticks to the stent but not the balloon; an iris which protrusions or sandpaper ideally designed to engage the stent
can be narrowed down to allow the balloon to slip by but not end or body but not the catheter balloon.
the stent; or nubs which contact the stent but not the balloon.
3.1.12 guide catheter, n—a tube designed to transport the 4. Significance and Use
guide-wire and the stent delivery system into the target vessel. 4.1 The securement of the endovascular stent on the balloon
3.1.13 guide-wire, n—a wire designed to aid in balloon, is a critical parameter to ensure that the stent is safely delivered
ultrasound, atherectomy, or stent placement during endovascu- to or from the treatment site.
lar procedures. 4.2 This guide is intended for use by researchers and
3.1.14 mandrel, n—a wire that may be used as an alternative manufacturers for the development and selection of pre-test
to the intended guide-wire to provide support for the catheter treatments, tests and test endpoints to measure stent secure-
guide-wire lumen for some test procedures. ment (displacement distances and dislodgment forces).

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4.3 This guide may be used to investigate which practical 6.2.1.2 Physician surveys for clinical relevance and prob-
combinations of in vitro tests best characterize clinical sce- lems with comparable devices.
narios. 6.2.1.3 Mechanical understanding of the tests’ clinical rel-
4.4 This guide should be used with discretion in choosing evance and limitations.
securement tests and evaluating results due to the myriad 6.2.1.4 Mechanical and statistical understanding of the test
possible combinations of clinical conditions, failure modes, reproducibility limitations due to device variation, pre-test
and stent delivery system designs. treatments, various grips, and test conditions.
4.5 This guide may be of use for developing a test for 6.2.1.5 Ability to set accept/reject criteria by physician
meeting parts 2 and 3 of the requirements of EN 14299, evaluation, by historical comparisons, or by other rational
Section 7.3.4.4 on Trackability. means.
4.6 This guide may be of use for developing a test to meet 6.2.2 The final securement test(s) selected must ultimately
section VII-C-8 of CDRH Guidance document. satisfy internal manufacturer quality standards. These stan-
dards may include clinical relevance, FMEA analysis, statisti-
5. Clinical Scenarios 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 regulatory body standards. For example, the FDA QSR 21 CFR
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 of design and manufacturing of finished devices “is suitable for
types of failures: its intended purposes and is capable of producing valid
5.1.1 Displacement or dislodgment of the stent while at- results.” For the statistical capability evaluation, Guide E1488
tempting to track through or position in tortuous bends, fibrous is very helpful.
or calcified lesions, or previously implanted stents, or combi- 6.3 Pre-Test Treatments:
nation thereof. 6.3.1 Pre-test treatments may be conducted prior to the
5.1.2 Displacement or dislodgment of the stent on with- evaluation of securement to simulate preparatory, environmen-
drawal of the undeployed stent delivery system back into the tal, mechanical, or other conditions that may be encountered
guide catheter, introducer sheath, or hemostasis valve. This prior to or during clinical use of the device.
failure type is usually associated with failure to cross tortuous 6.3.2 Pre-test treatments may include subjecting the devices
bends, fibrous or calcified lesions, or previously implanted to shelf life testing, sterilization, elevated shipping
stents, or combination thereof. It is sometimes associated with temperature/humidity, removal of the delivery system from the
less-than-ideal seating or angled placement of the guide carrier tube, and other catheter preparation per use instructions,
catheter tip in the ostium of the vessel. pre-soaking, bending treatments, tracking treatments, and
5.1.3 Displacement or dislodgement of the stent due to tracking through lesion treatments.
improper catheter preparation including mishandling or partial 6.3.3 Tracking treatments are intended to clinically simulate
balloon inflation during preparation. This has been identified in the bending and frictional forces of tracking the device through
a few cases where the loose, displaced, or dislodged stent was the guide catheter and vasculature to the lesion site. Consider-
observed prior to use but may conceivably play a role in a ations for tracking treatments include: tracking medium (for
small percentage of cases where dislodgment occurs in pa- example, air, water, water with lubricants, saline, blood) and
tients. temperature; guide catheter and guide-wire selection; simu-
lated vessel material (for example PMMA, silicone, glass,
6. Test Method Considerations PTFE), tortuousity, dimensionality, length and diameter; speed
6.1 Flowchart—See Fig. 1. of tracking; and number of repetitions to track. Angiograms or
6.2 Development and Evaluation of Securement Tests: autopsies of human or similar animal vasculature may be
6.2.1 Securement test development and selection is ideally particularly useful in developing alternative anatomical mod-
begun through the initial use of a battery of tests measuring a els. An example of a tracking treatment is given in Section 7.
variety of failure modes. These test methods may vary from a Two examples of tracking fixtures are given in engineering
simple intuitive tactile impression of the securement forces diagrams in the Appendix. Note that these engineering dia-
through manipulation to clinically modeled situations with grams simulate vessels in 2-D with a moderately difficult
guide catheters and stenosis models to in vivo animal studies degree of coronary tortuousity but do not include simulated
with representative anatomy and physician handling. From a lesions.
safety-risk perspective, consider how securement challenges 6.3.4 Tracking through lesion treatments are intended to
may occur in clinical situations, what may result from loss of clinically simulate the bending, frictional and mechanical
securement, what the severity of the outcome is to the patient, resistance forces of tracking the device across the lesion site.
what the frequency of these situations are, and then how to test Considerations include those of tracking treatments in addition
to detect these occurrences. Factors to consider in evaluating to simulating the lesion material, type, and morphology. Lesion
securement tests include the following: material encountered clinically may include calcium, fibrin,
6.2.1.1 Review of the MAUDE database for reported prob- collagen, fat, cholesterol, endothelial cells, smooth muscle
lems with comparable devices. cells, red blood cells, platelets, dead white blood cells, and

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 F2394 – 07

FIG. 1 Flowchart

macrophages. Lesion types may be calcified, fibrous, lipidic, adjunct to force measuring tests. In particular, the measurement
thrombotic, or grumous. Lesion morphologies may be totally of end flaring may be useful. While end flaring may increase
or partially occluded, concentric or eccentric, focal or diffuse, the chance the stent will catch on a guide, previously placed
and of many possible shapes. stents, lesions, and so forth, end flaring does not, in itself
6.3.5 Post-Track Test Evaluation—To understand the effects determine the force it takes to displace, dislodge or deform the
of tracking on the probability that the stent delivery system stent. End flaring and other geometrical changes also provide a
may encounter securement challenges, the measurement of measure of the effects of different track and lesion geometries
stent-balloon geometry changes post tracking may be a useful and materials. End flaring may be measured by measuring the

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 F2394 – 07
change in peak proximal and distal end heights relative to the consistency and simplicity by executing the remaining testing
longitudinal continuation of the nominal stent diameter. with the optimal selection.
6.4 Securement Test and Grip Methods: 6.5.3 The gauge length chosen may influence the pull rate
6.4.1 There are two main categories of stent securement transmitted to the stent. A shorter gauge length will have less
tests: guide-types and lesion-types. longitudinal material deformation and transmit a less variable
6.4.2 A guide-type securement test simulates the clinical pull rate closer to the set pull rate. A 25 mm gauge length is a
scenario of pulling an undeployed stent delivery system back typical value.
into a guide catheter, arterial sheath or hemostasis valve. 6.5.4 The pull rate selected should allow meaningful dis-
Examples of grip methods used to simulate guide-type secure- crimination and measurement of the chosen test endpoint(s)
ment tests include guide catheters, rings, or shims ideally and, as possible, model the clinical situation. Slower rates may
designed to engage the stent end or body but not the catheter help visualizing pull-off mechanics in video taped tests. Faster
balloon. The shim securement test, described in Section 7, uses rates may be more repeatable. In a test modeling lesion
complementary thin, rigid plates with rounded “V” notches to dislodgment, set the crosshead extension speed (pull rate) to a
circumferentially engage the stent end but not the catheter slow rate such as at 0.5 in./min. In a test modeling withdrawal
balloon. Engineering diagrams are included in the Appendix. into the catheter, set the crosshead extension speed to a faster
6.4.3 A lesion-type securement test simulates the clinical rate such as 10 to 30 in./min. Adjust the data sampling rate as
scenario of pushing or pulling an undeployed stent delivery appropriate; for example, increase the sampling rate for high
system through or around a fibrous or calcified lesion. Ex- pull speeds; have a high sampling rate for measuring peak
amples of grip methods used to simulate lesion-type secure- forces.
ment tests include tape, nubs, protrusions, or sandpaper ideally 6.5.5 The direction of pull (proximally, distally, or angled)
designed to engage the stent end or body but not the catheter chosen may depend on factors such as stent and delivery
balloon. system design and clinical relevance. The product design may
6.4.4 For both types of tests, it may increase the understand- be more at risk for either proximal or distal displacement.
ing of the test to measure a baseline reference force by testing Clinically, peak pull forces transmitted to the stent will exceed
delivery systems without or with poorly secured stents. Such push forces. Also, the stent forces encountered clinically are
tests may provide measurements of slip forces, balloon and seldom oriented purely proximally or distally tangent to the
catheter deformation mechanics, and the lower limit to mea- undeformed stent axis. Pulling in a non-tangential direction
surable securement forces. adds in normal forces which tend to increase the displacement
6.5 Test Conditions: and dislodgement forces. Thus, typically, the most challenging
securement test pulls purely in the tangential direction of the
6.5.1 Stent securement test conditions particularly impor-
undeformed stent. This is best confirmed through systematic
tant for hygroscopic balloon materials, whose stent securement
variation of the pull direction.
properties may change with varying exposure to water or other
fluids, include the following: 6.6 Test Endpoints:
6.6.1 There are two main test endpoints for stent securement
6.5.1.1 Tracking and test temperature,
evaluations: displacement force and dislodgment force.
6.5.1.2 Tracking and test medium (for example, air, water,
6.6.2 The displacement force is the force required to dis-
saline, blood),
place the stent with respect to the balloon in a non-recoverable
6.5.1.3 Tracking and test soak time (for fluid mediums), and movement. Clinically, displacement may result in the follow-
6.5.1.4 Time between track and test. ing:
NOTE 1—Justification for the selection of the parameters should be part 6.6.2.1 Improper positioning upon deployment due to the
of the test history file. movement of the stent with respect to the markerbands,
6.6.2.2 Incomplete stent end deployment due to movement
6.5.2 Guide-wire selection (or substituted test mandrel) may
of the stent off the body of the balloon, and
particularly influence pre-test track treatments and securement
6.6.2.3 Incomplete or poor apposition of the stent to the
tests that include simulated tracking. A stiffer guide-wire or test
vessel walls due to compression or buckling damage to the
mandrel may place the stent delivery system under greater
stent.
normal and frictional forces. Or, it may span and round out
curvature in a track model, especially flexible models, and NOTE 2—There are at least four possible endpoints to measure displace-
reduce the bending of the balloon and stent. Additionally, ment force: initial, critical distance peak, initial peak, and maximum
guide-wire stiffness varies along the length (for example, sustained force. See Fig. X2.1 for graphical representation of the first three
flexible 50-mm tip, moderate 50-mm stent/balloon support, and of these listed endpoints. The maximum sustained force (not seen in Fig.
X2.1) may be relevant for some stent, balloon, and test combinations.
stiff 500-mm shaft); guide-wire materials may have strong
non-linear response and recovery from bending, and each 6.6.2.4 The initial displacement force is the initial force
different guide-wire surface, typically chosen for lubricity and required to displace the stent with respect to the balloon. This
durability, may respond to different catheter lumen surfaces. is often difficult to distinguish from movement of the stent
Completing ruggedness evaluations using a variety of wires within but not out of its balloon imprint or movement of the
may be important to determine the optimal wire choice for the intact stent and balloon with respect to, for example, the
test. However, after choosing the optimal wire within the guide-wire lumen and markerbands within the balloon. There
guidelines of the Instructions for Use for your stent, maintain may be operator variability in the assessment of the force at

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 F2394 – 07
which initial displacement occurs. This endpoint is a conser- 7.1.2 Securement-Testing Machine—A power-driven ma-
vative estimation of the force at which clinically significant chine capable of the following:
negative outcomes may occur. 7.1.2.1 Uniform crosshead speed (pull rate) within 5 % of
6.6.2.5 The initial peak displacement force is characterized set rate,
as the first peak in force that occurs during or after stent 7.1.2.2 Measurement and recording of force exerted to a
displacement with respect to the balloon. A peak displacement precision of 0.01 lbf, and
force may often occur simultaneously with stent displacement 7.1.2.3 Measurement and recording of crosshead displace-
and would therefore be equal to the initial displacement force. ment to a precision of 0.01 in. or time measured to a precision
However, for some stent delivery systems, the stent may move of 0.1 s.
a critical distance before a peak in force is reached. Therefore
7.1.3 Crosshead Catheter Clamp—Wedge clamps or other
the initial peak displacement force is a conservative estimation
clamps attached to the machine crosshead capable of holding
of the dislodgment force.
the catheter beyond the securement endpoint without slipping.
6.6.2.6 The critical distance peak displacement force is the
7.1.4 Fixed Shim Stent Grips—An example of the fixed
maximum force required to displace the stent with respect to
shim stent grips and associated tooling is given in engineering
the balloon a critical distance. This critical distance should be
diagrams in the Appendix, Figs. X2.5-X2.8.
the minimum of the following two distances.
(1) The distance at which the undamaged stent could 7.1.5 Water Bath—Vessels used to immerse the tracking
overhang the balloon body resulting in a clinically significant, fixture and the securement test stent grips in 37 6 2°C water.
incomplete deployment of the overhanging end of the stent, 7.1.6 Camera and Video Recorder—Optional devices used
and during the securement testing to help determine the stent
(2) The length (distance) of stent compression or buckling securement test endpoint.
that could result in a clinically significant, incomplete deploy- 7.2 Test Specimens:
ment of the deformed stent against the vessel walls. 7.2.1 To establish a sufficiently powered test, first determine
the standard deviation. This can be established by running a
NOTE 3—The critical distance displacement force may often be equal to trial to estimate the variation or by leveraging existing data.
the initial displacement force. There may be operator variability in the
assessment of the critical distance within which to determine the maxi-
Further, calculate the required sample size with this standard
mum force. Due to this operator dependence, there may be significant deviation, the desired minimum detectable difference, mini-
variance between operators. mum significance level and minimum power level.
NOTE 4—The clinical significance of incomplete deployment may 7.2.2 Unless otherwise justified, all samples selected for
depend on several factors, particularly time and the location at which the testing should be taken from finished, sterilized, clinical-
incomplete deployment occurs; for example, dislodgement during inser- quality product. Cosmetic rejects or other non-clinical samples
tion into a coronary lesion is more critical than dislodgement on
may be used for these tests if the cause for rejection is not
withdrawal through a hemostasis valve.
related to securement.
6.6.3 The peak dislodgment force is the maximum force 7.2.3 Prepare the device in accordance with the Instructions
required to completely dislodge the stent from the delivery for Use.
system balloon. Clinically, if the stent is dislodged distally, this 7.3 Pre-Test Treatment Procedure:
endpoint represents the stent embolizing in the vasculature. If
7.3.1 Set the tracking fixture, with the guide catheter and
the stent is dislodged proximally, the balloon can no longer be
guide-wire inserted, in the 37°C water bath. Guide catheter and
used to deploy the stent. The majority of reported securement
guide-wire selection should be consistent with the devices used
problems are associated with stent dislodgement. Though peak
during medical procedures for the device tested.
dislodgment force is operator independent, it still may have
significant variability, particularly for stent delivery systems 7.3.2 Advance the delivery system through the guide cath-
with catch-points such as unfurled balloon cones or other eter and the tracking fixture. Fully track the system into the
raised profile components abutting the distal or proximal end, fixture in 2 to 8 seconds. Withdraw it at approximately the
or both, of the stent. Since dislodgement occurs after displace- same rate. For a worst case in loosening the stent on the
ment, the peak force is of secondary importance to the balloon, track the device three or more times.
dislodgement distance prior to stent deployment and of primary 7.3.3 Remove the system from the tracking fixture and store
importance if the stent/stent delivery system is being removed. on a catheter rack at room temperature.
Dislodgement force is a vital characteristic but is not a 7.4 Securement Test Procedure:
complete measure of securement. 7.4.1 Set up the shim stent grips within the water bath at a
temperature of 37 6 2°C.
7. Examples of Apparatus and Procedure 7.4.2 If used, set up the camera and video recorder to allow
7.1 Apparatus Example: clear display of the stent/shim interface.
7.1.1 Pre-Test Treatment Tracking Fixture—An example of 7.4.3 Set the crosshead extension speed (pull rate) at 2
the fixture is given in the engineering diagrams in the Appen- in./min.
dix, Figs. X2.1 and X2.2. Note that this model simulates a 7.4.4 Insert a suitable guide-wire or test mandrel into the
coronary vessel in a 2-D plane with a moderately difficult catheter lumen so that it will extend at least from the catheter
degree of tortuousity but no simulated lesions. clamp point to the tip of the catheter.

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 F2394 – 07
7.4.5 Insert catheter through the open “V” of the shims and 8.4.1.4 Performance compared to historical data or against
close the shims over the folded balloon at the proximal end of other stent delivery system designs, models, or sizes.
the stent. 8.4.2 Test scenario:
7.4.6 Check shim size. Shims should be sized to allow the 8.4.2.1 Simulated use conditions.
delivery system balloon to move freely while the stent remains 8.4.2.2 Comparative bench testing which emphasizes re-
blocked from moving through the shims. Remove and replace peatability and the ability to discriminate products and de-
shims as necessary to obtain proper fit. emphasizes actual use conditions.
7.4.7 Secure crosshead catheter clamp at 1.0 6 0.1 in. 8.4.2.3 Challenge testing which combines 2 or more low
proximal to the proximal edge of the stent (1 in. gauge length). probability events/situations to create an unlikely condition in
7.4.8 Start video recorder, if used. which it is likely the performance of the device will decrease.
7.4.9 Start machine crosshead extension.
8.4.3 Characteristics to be evaluated:
7.4.10 Monitor test to observe chosen test endpoint.
8.4.3.1 Stent securement performance.
7.4.11 Record the securement endpoint(s), force and mode
(for example, stent slippage or buckling). 8.4.3.2 Changes in stent geometry with tracking and/or
7.4.12 If the stent pulls through the shim ID, the peak force securement testing.
is a false representation of stent securement and should be 8.4.3.3 Specific stent securement or safety mechanisms.
recorded as invalid data. The stent delivery system should not 8.4.3.4 Conclusions to be made based on the results of the
be retested. testing, especially accept/reject criteria.
8.5 References/Supporting Documents:
8. Test Report 8.5.1 Test protocol (what is to be done), test method (how),
test method development reports (how you know the test
NOTE 5—The following is a content recommendation for stent secure-
ment test reports. The documentation should be clear enough so that the method is suitable and capable for intended purpose), and data
study could be repeated. sheets.
8.5.2 As required, reference equipment calibration and
8.1 Test Report Identification:
maintenance logs, and operator training records.
8.1.1 Report title; author, contributors and their affiliations;
8.6 Test Specimens/Materials/Traceability:
name of organization presenting the results; date of publica-
tion; any additional document identifiers, such as a document 8.6.1 Identification:
number, as required by the organization or reviewing bodies. 8.6.1.1 Stent: length, diameter, coatings or treatments.
8.1.2 Product(s) tested. 8.6.1.2 Stent delivery system—If a balloon catheter, indica-
8.2 Executive Summary: tion of balloon material characteristics (for example, compliant
8.2.1 Summarize the nature and scope of the testing. versus non-compliant); monorail, over-the-wire, combination
8.2.2 Summarize conclusions made as a result of the testing, device, or other; and the stent delivery system coatings or
especially claims pertaining to safety. treatments.
8.3 Objective: 8.6.1.3 Accessory devices used, for example, guide-wires.
8.3.1 Identify the types of specimens being tested: 8.6.1.4 Traceability—Provide sufficient information so that
8.3.1.1 Labeled stent length and diameter. processing records can be found for the test specimens—as full
8.3.1.2 Monorail, Over-the-Wire, or other type of delivery assemblies, partial assemblies, the assembly processes, and
system. sterilization/conditioning records, as appropriate.
8.3.1.3 Devices with special characteristics or histories. 8.6.2 Processing and conditioning of the stent, the delivery
8.3.1.4 Actual or representative finished goods or special system, and the finished device.
builds. 8.6.2.1 Pilot line or production line manufacturing.
8.3.2 Identify the type(s) of testing being performed: 8.6.2.2 Nominal or limit processing conditions, repeated
8.3.2.1 Product Specification Testing—Determine if the cycles, or challenge conditions.
product performance meets the requirements of the product 8.6.2.3 Actual or simulated handling, shipping, or storage
specification. conditions.
8.3.2.2 Manufacturing Control Testing—Determine if the 8.6.2.4 Time between critical processes, if applicable.
performance of the product is within normal tolerance and if
8.6.2.5 Special processes not typical to the design.
there is no significant trend towards being out of control.
8.3.2.3 Other Types of Testing—Predicate device compari- 8.6.2.6 Rationale for choosing such test specimens if not
son testing; design alternative testing, observational testing, obvious.
test method development. 8.7 Sample Size:
8.4 Scope: 8.7.1 Sample size(s) and the sample size rationale based on
8.4.1 Identify what the test will demonstrate: significance level, confidence level, and power level as appro-
8.4.1.1 Stent securement as a stand-alone characteristic; priate.
8.4.1.2 The ability to retract the stent delivery system intact 8.7.2 Sampling technique—such as per a specified random
after stent securement is challenged; process, first and last product in each sequential lot, special
8.4.1.3 The ability to deploy the stent after stent securement built.
is challenged; and/or 8.8 Experimental Method:

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8.8.1 Test method overview with emphasis on specific 8.10 Conclusions:
choices made within the referenced test method or deviations 8.10.1 As appropriate, was the acceptance criteria met?
to the referenced test method. 8.10.2 Do the results support claims made about the device
8.8.2 Data collected during the test, noting which data are with regard to performance?
objective and which are observer-dependent. 8.10.3 Was anything notable or unexpected observed?
8.8.3 Retrospective information detailing the process for 8.10.4 Recommendations for future tests or future testing,
processing, analyzing, and presenting data, and if there were as appropriate.
any deviations from the test method. 8.11 Appendices:
8.9 Results: 8.11.1 Test protocol, test method, individual data, and/or
8.9.1 Data table(s) including max, min, means, standard calculations, as appropriate.
deviations, and number of samples, as appropriate.
8.9.2 Graphs—plots of actual measured data and, as appro- 9. Keywords
priate, means and standard deviations. 9.1 angioplasty; artery; dislodgment; displacement; medical
8.9.3 Discussion of results. device; retention; securement; stent; vascular

APPENDIXES

(Nonmandatory Information)

X1. RATIONALE

X1.1 Beginning with an understanding of the clinical relevant as well as repeatable and reliable. The guide asks the
conditions which may lead to stent dislodgement or stent user to consider the many product life-history pre-test treat-
deformation, this guide describes a development process and ments of the test specimen that may affect the results. The
many considerations in stent securement testing. The guide guide also discusses some details of the test conditions and the
shows a method to develop one or more tests that are clinically detail of how to interpret numerical results from the test.

X2. ENGINEERING DIAGRAMS

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A = initial displacement of stent with respect to balloon,

B = initial peak displacement force,
C = critical distance peak displacement force,
D = critical distance of stent displacement, and
E = dislodgement force.
FIG. X2.1 Stent Securement Test Force versus Displacement—Stent Securement Graph

FIG. X2.2 Bottom Plate of the Test Tracking Fixture for Conditioning the Stent, Balloon, and Stent Securement System

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FIG. X2.3 Top Plate of the Test Tracking Fixture for Conditioning the Stent, Balloon, and Stent Securement System

FIG. X2.4 Alternative Test Tracking Fixture

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FIG. X2.5 Stent Securement Shim Grip Test Assembly

FIG. X2.6 Stent Securement Shim Grip Base

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FIG. X2.7 Stent Securement Shim Grip Holder

FIG. X2.8 Stent Securement Shims

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X3. EXAMPLES OF TEST METHOD DESIGN CONSIDERATIONS

X3.1 Sampling—Since the securement test irreversibly nificant variations in test results occur with different operators,
changes the test samples such that the same samples cannot be different time points, a range of devices, and/or with other
used more than once, the variation in the individual results sources of random variation. The range of devices may include
cannot distinguish between uncontrolled variation in the test carefully selected devices to minimize part-part variation,
samples and uncontrolled variations associated with the equip- devices or model devices such as rings on rods. Along with
ment, operators, or environment. However, with sufficient this, if more than one machine is used, or if fixtures change,
numbers of random samples from the same population and a measure the machine variability and the effects on repeatability
good test design, the distributions of results can be used to and reproducibility.
distinguish the effects of controllable factors. Thus, prior to
testing, plan your test to efficiently and confidently resolve X3.5 Capability—Determine the operating range of the test.
differences in results due to controllable factors. In particular, For example, determine a range of diameters, lengths, materi-
determine the number of samples required for the level of als, designs, or other factors which are suitable for evaluation
confidence and power desired. The power is the probability by this test. A secondary outcome of this determination may be
that a specific mean difference will be detected. For example, the characterization of an entire family of stent systems and the
if the test objective is to determine whether a normally identification of a worst-case for further analysis.
distributed mean is greater than a specific benchmark, the
sample size may be calculated as a function of four inputs: (1) X3.6 Bias—Since it is unlikely there will be an accepted
the estimated standard deviation, (2) the desired minimum reference value of securement, it is recommended that exter-
detectable difference between the mean and the benchmark, (3) nally circulated test reports provide comparisons between
the desired significance level, and (4) the desired power. A existing products (predicate devices) and the device of interest.
significance level of 0.05 to 0.10 and a power level of 80 to However, new modes of failure may occur with new design
90 % are frequently used. features, for example, change from bare to coated stents, so old
test methods, mean values and distributions may all appropri-
X3.2 Suitability—If the test is to be clinically predictive, ately change making comparison with predicate devices unre-
demonstrate that the securement test models simulate either liable and not useful.
access through a lesion or a withdrawal into a guide catheter.
Alternatively, the purpose of the test may be to assess manu- X3.7 Validation—The validation activities for a test method
facturing repeatability. depend on the criticality and the complexity of the test method.
That is, the more complex the test, the more work will be
X3.3 Ruggedness—Using Guide E1169, determine the sen-
required to understand the method, understand the sources of
sitivity of the test results to deliberate small variations in the
variation (test or specimen), and choose appropriate test
test conditions and environmental factors. If any effects are
parameters. The more critical the need for the test (that is, is a
statistically significant relative to inherent measurement vari-
measured test characteristic merely annoying or potentially
ability then modify the test method to reduce these effects, that
life-threatening compounded by the frequency of occurrence),
is, make the test more robust.
the more thorough the demonstration that the test method is
X3.4 Repeatability and Reproducibility—Determine if sig- relevant and predictive.

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