ISO 7198:1998

INTERNATIONAL ISO
STANDARD 7198
First edition
1998-08-01
Cardiovascular implants — Tubular
vascular prostheses
Implants cardiovasculaires — Prothèses vasculaires tubulaires
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Reference number
Contents
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 General requirements.5
5 Requirements for finished prosthesis.10
6 Requirements for in vivo preclinical and clinical evaluation .14
7 Sampling.15
8 Test methods for vascular prostheses.16
9 In vivo preclinical and clinical test methods for vascular prostheses.42
10 Information to be recorded and disclosed by the manufacturer on request.48
©  ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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ISO ISO 7198:1998(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
International Standard ISO 7198 was prepared by Technical Committee ISO/TC 150, Implants for surgery,
Subcommittee SC 2, Cardiovascular implants.
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Introduction
ISO 7198 has been prepared in order to provide basic requirements for sterile vascular prostheses and the methods
of test which will enable evaluation of vascular prostheses.
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INTERNATIONAL STANDARD  ISO ISO 7198:1998(E)
Cardiovascular implants — Tubular vascular prostheses
1 Scope
1.1  This International Standard specifies requirements relating to testing, packaging, labelling and terminology for
sterile tubular vascular prostheses intended to replace, bypass or to form shunts between segments of the vascular
system in humans.
This International Standard addresses vascular prostheses that are made wholly or partly of: materials of biological
origin; synthetic textile materials; and synthetic nontextile materials. In addition, guidance for characterization of
compound and composite prostheses is provided. It specifies the designation of materials of manufacture and the
construction, and specifies the designation of sizes and dimensions of vascular prostheses. It refers to biological
requirements of the materials of construction and of the finished product, taking into account the appropriate part of
the horizontal International Standard ISO 10993.
This International Standard also specifies the designation of mechanical properties. It describes methods for the
measurement and verification of the dimensions and mechanical properties declared by the manufacturer. It refers
to sterilization of prostheses and specifies requirements for labelling and packaging. It also provides definitions of
terms in common use.
This International Standard does not specify all the performance or dimensional characteristics, but it does
1.2
include methods for verifying that the nominal values disclosed by the manufacturer are within the permitted
tolerances. These recommendations do not purport to comprise a complete test program.
For the purposes of this International Standard, the disclosure of test methods, results and other information on
1.3
request shall relate solely to requests from a National Regulatory Authority with responsibility for surgical implants.
This International Standard does not apply to human donor tissue devices such as cryopreserved vessels. Also
excluded are all patches, pledgets and stents.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 472:1988, .
Plastics — Vocabulary
ISO 2076:1989, Textiles — Man-made fibres — Generic names.
ISO 2859-1:1989, Sampling procedures for inspection by attributes — Part 1: Sampling plans indexed by
acceptable quality level (AQL) for lot-by-lot inspection.
ISO 2859-2:1985, Sampling procedures for inspection by attributes — Part 2: Sampling plans indexed by limiting
quality (LQ) for isolated lot inspection.
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ISO 2960:1974, Textiles — Determination of bursting strength and bursting distension — Diaphragm method.
ISO 5081:1977, Textiles — Woven fabrics — Determination of breaking strength and elongation (Strip method).
ISO 5084:1977, Textiles — Determination of thickness of woven and knitted fabrics (other than textile floor
coverings).
ISO 10993-1:1997, Biological evaluation of medical devices — Part 1: Evaluation and testing.
ISO 14155:1996, Clinical investigation of medical devices.
ASTM D 76-93, Specification for tensile testing machines for textiles.
ASTM D 123-94, Terminology relating to textiles.
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in ASTM D 76-93, ASTM D 123-94
and the following apply.
3.1
allograft (adj.: alloplast)
implant material made from tissues of an animal of the same species
3.2
bifurcation
site of division of one vascular tube (trunk or body) into two branches (limbs)
3.3
biological material
material of animal or vegetable origin that may have been modified or treated by chemical processes, but excluding
any material derived from fossil biological remains (e.g. petroleum oil)
3.4
biostability
ability of a material to maintain its physical and chemical integrity after implantation in living tissue
3.5
coating
any organic or inorganic material, other than living cells, intentionally applied by a manufacturer to a substrate
prosthesis.
NOTE  This coating may be intended to be permanent or temporary, may be applied to the external and/or internal surface,
and/or may be impregnated into the structure of the substrate
3.6
compliance
ability of a prosthesis to elastically expand and contract in the circumferential direction in response to a pulsatile
pressure
3.7
component
substance used during manufacture whether or not it is intended to remain as a consistent element of the device
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3.8
composite prosthesis
vascular prosthesis in which the construction and/or material of construction varies in a segmental manner along
the length
cf. compound prosthesis (3.9)
EXAMPLE  Prosthesis in which the proximal portion is of crimped knitted fabric and the distal portion is of an aldehyde-treated
animal vascular tube.
3.9
compound prosthesis
vascular prosthesis whose wall is uniformly constructed of materials from more than one source
cf. composite prosthesis (3.8)
3.10
configuration
geometry of prosthesis
EXAMPLES  Straight, bifurcate, tapered.
3.11
construction
type of structure of a prosthesis
EXAMPLES  Knitted, woven, nonwoven, expanded polymer.
3.12
crimp
creases or folds manufactured into a prosthesis to permit elongation and reduce kinking
3.13
fibril
strand of material which originates from one or more nodes and terminates at one or more nodes
3.14
host
recipient of an implant
3.15
implantable state
condition of a prosthesis that has been prepared in accordance with the manufacturer's instruction prior to
implantation, or of a material of construction that has undergone the same process of sterilization and/or preparation
NOTE  Preparation does not include preclotting (see 3.20), but does include any recommended method of washing or soaking.
3.16
integral water permeability
volume of clean, filtered liquid (with a viscosity approximating that of water) which passes through the wall of a
prosthesis in a specified time under a specified pressure
3.17
leakage
volume of clean, filtered liquid (with a viscosity approximating that of water) which passes through flaws in a
water-impermeable vascular prosthesis in a specified time under a specified pressure
NOTE 1  Leakage may be either through small defects in the wall of a continuous tube or through an anastomosis constructed
by the manufacturer.
NOTE 2  Leakage is not the same as porosity (3.19).
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3.18
node
solid region within a material at which fibrils originate and converge
3.19
porosity
estimate or index of the ratio of the void within a material to the total volume occupied by the material including the
voids
NOTE 1  Porosity may be expressed as the percentage void to the total area of volume, mean distance between nodes, or
mean pore diameter.
NOTE 2  Porosity is not the same as leakage (3.17) or water permeability (3.34).
3.20
preclotting
procedure whereby blood or blood fractions are allowed to penetrate and coagulate within the interstices of a
porous prosthesis to decrease the permeability
3.21
primary component
substance incorporated into the finished prosthesis whose addition is designed by the manufacturer to improve the
performance of the device
3.22
prosthesis (plural: prostheses, adj.: prosthetic)
any device which replaces or substitutes for an anatomical part or deficiency
3.23
residual material
substance that is employed in the manufacture of the prosthesis, but is intended to be removed or is not required in
the finished prosthesis
3.24
secondary component
substance that may be incorporated into the finished prosthesis, but is not primarily responsible for the stated
function
3.25
substrate prosthesis
vascular prosthesis to which a coating meeting the definition of 3.5 is applied
3.26
synthetic material
substance of nonbiological source that is produced and/or polymerized by chemical or physical means
NOTE  Chemically modified materials derived from fossil biological remains, e.g. petroleum or oil, are considered to be
synthetic.
3.27
synthetic nontextile prosthesis
vascular prosthesis manufactured using nontextile processes
EXAMPLES  Prostheses made from extruded polymer, expanded polymer.
3.28
synthetic textile prosthesis
vascular prosthesis made from synthetic yarns using textile fabrication methods
EXAMPLES  Prostheses made by knitting, weaving, braiding of synthetic yarns.
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3.29
usable length
length of a prosthesis available for implantation, determined under a specified fixed load
NOTE  The load may be zero for certain prostheses.
3.30
vascular prosthesis
vascular graft
prosthesis used to replace, bypass, or form shunts between sections of the vascular system
3.31
velour
fabric with a cut or looped pile or with a napped surface
3.32
void
proportion of the wall of a vascular prosthesis that is not occupied by the material of construction
cf. porosity (3.19)
NOTE  That is, the interstices of a knitted or woven structure.
3.33
water entry pressure
pressure at which water passes from the inner wall to the outer wall of a vascular prosthesis
3.34
water permeability
water porosity
volume of clean, filtered water that passes during a specified period through a unit area of the prosthetic material
under a specified pressure
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NOTE 1  The water permeability is usually determined as ml⋅cm ⋅min at an applied pressure of 16 kPa (120 mmHg).
NOTE 2  Water permeability is not the same as porosity (3.19)
3.35
xenograft (adj.: xenoplast)
heterograft
implant material made from the tissues of an animal of a different species from the host
4 General requirements
The following requirements should apply to all vascular prostheses, regardless of origin.
4.1 Configuration and size designation
The configuration of a vascular prosthesis shall be designated by its geometry, e.g. straight, bifurcated or tapered.
NOTE  Some prostheses may be manufactured for specific applications, such as an axillo-bifemoral prosthesis, and should be
designated by their intended clinical use, not as `bifurcated.'
4.1.1 Uniform straight vascular prostheses
The size of a straight uniform vascular prosthesis shall be designated by the following characteristics:
a) nominal relaxed internal diameter of the device, expressed in millimetres;
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b) nominal pressurized internal diameter of the device, expressed in millimetres, under a distending pressure of at
least 16 kPa (120 mmHg), if this diameter changes by more than 10% while under pressure (see 5.6);
c) minimum usable length, expressed in centimetres.
4.1.2 Bifurcated uniform vascular prostheses
The size of bifurcated uniform vascular prostheses shall be designated by the nominal relaxed internal diameters
and the minimum usable overall length of the main tube and its branches, expressed in centimetres. Pressurized
internal diameters shall also be designated if required [see 4.1.1 b)].
4.1.3 Tapered vascular prostheses
The size of a tapered vascular prosthesis shall be designated by the nominal relaxed internal diameters of its ends
and its minimum usable length, both expressed in centimetres. Nominal pressurized internal diameters shall also be
designated if required [see 4.1.1 b)].
4.1.4 Other configurations
For other configurations (e.g. an axillo-bifemoral prosthesis), the principal length(s), the nominal relaxed internal
diameter(s), and the nominal pressurized internal diameter(s), if required, shall be designated, and expressed in
millimetres or centimetres as required.
4.2 Intended clinical use designation
The intended clinical use shall be designated by one or more of the following:
a) thoracic aortic and/or thoraco-abdominal;
b) abdominal aortic and/or aorto-iliac, and/or aorto-femoral;
c) peripheral arterial, including extra-anatomic (e.g. axillo-femoral arterial);
d) coronary arterial;
e) arterio-venous shunt for vascular access;
f) other vessels to be specified.
4.3 Materials and construction
4.3.1 Classification
The classification of a prosthesis shall be designated by one of the following:
a) synthetic textile (e.g. knitted, woven);
b) synthetic nontextiles (e.g. extruded polymer, expanded polymer);
c) biological (e.g. allograft, xenograft);
d) compound;
e) composite.
4.3.2 Nomenclature
4.3.2.1 Synthetic materials
Synthetic materials shall be described by:
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a) their generic or chemical name, in accordance with ISO 472 or ISO 2076;
b) the general nature of any chemical treatment or modification.
4.3.2.2 Biological materials
Biological materials shall be described by the following information:
a) the origin of the material as the genus of the donor animal, in adjectival form;
b) the type and site of the tissue (e.g. umbilical vein; carotid artery) or the type of material (e.g. collagen, albumin);
c) the general nature of any chemical treatment or modification;
d) the specific characterization of any biological material (e.g. the degree of crosslinking) that shall be disclosed
by the manufacturer on request.
4.3.2.3 Coatings
For a coating, the amount, permanence, uniformity shall be determined.
Coatings shall be described by the following information, as appropriate:
a) the nomenclature of any synthetic component(s) in accordance with 4.3.2.1;
b) the nomenclature of any biological component(s) in accordance with 4.3.2.2.
4.3.2.4 Storage fluids
Storage fluids shall be described by the following information:
a) the generic or chemical name of the principal component(s);
b) the nature and type of possible toxic hazards.
NOTE  Attention is drawn to the existence of various international and national requirements with respect to maximum
permitted levels of potentially toxic materials.
4.3.2.5 Residual chemicals
NOTE  Residual chemicals refer to those processing and/or storage fluids or their derivatives that can be extracted from a
prosthesis in the implantable state (see 3.15).
Residual chemicals shall be described by their specific chemical names wherever possible; otherwise, their general
chemical nature shall be used.
4.4 Biocompatibility and biostability
4.4.1 Biocompatibility
Materials of which the prosthesis is made shall have been evaluated for biocompatibility in the implantable state
either individually or as part of the finished prosthesis in accordance with the principles and methods recommended
in ISO 10993-1.
Details of test methods and the results obtained shall be disclosed by the manufacturer of the prosthesis on
request.
Reassessment shall be made whenever changes are made in materials or in significant processing methods.
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4.4.2 Biostability
When the design of a prosthesis and its intended use as a chronic implant require that the prosthesis maintain some
minimum level of physical and chemical integrity after implant in living tissue for some time interval, the materials of
which the prosthesis is made shall be tested either individually or as part of the finished prosthesis.
A rationale for the test methods and the measured biostability shall be disclosed by the manufacturer on request
and may include:
a) the durability of materials currently used for the same indication;
b) the amount of time such a prosthesis is expected to perform in its indication for use, with consideration given to
the performance and clinical utility of other prostheses and other forms of treatment currently available to treat
the targeted indication;
c) whether there are currently prostheses or other forms of treatment for the targeted indication.
These considerations would, in some cases, be addressed by some form of risk-to-benefit analysis.
4.5 Sterility
The prosthesis shall be supplied sterile.
NOTE  The particular problems of transfer of infective agents by prostheses of animal, including human, tissue should be
taken into account when validating sterilization processes.
4.6 General information and instructions for use
Each unit container or outer container of which the contents are identical shall be supplied with instructions for the
use of the prosthesis. The instructions shall include the following:
a) indications for use;
b) contraindications, cautions, and warnings that are applicable;
c) recommended methods for the aseptic presentation and the preparation of the prosthesis for implantation,
including any pretreatment such as prewashing, preclotting, and/or implantation techniques, if applicable;
d) the statement STERILE DO NOT RESTERILIZE SINGLE USE ONLY in prominent form, if applicable;
e) resterilization information, if applicable;
f) notification of additives and/or leachable components, if applicable;
g) recommendations for storage, if applicable;
h) date of or reference relating to the publication of the text, indicating if the text has been revised.
4.7 Packaging
4.7.1 Unit container
Each prosthesis shall be packaged in a unit container. The unit container shall be so designed that it shall be readily
apparent once the unit has been opened.
For prostheses supplied sterile, the unit container shall be designed to maintain the sterility of the prosthesis under
nominal conditions of handling, transit, and storage, and to permit the contents to be presented for use in an aseptic
manner.
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4.7.2 Outer container
Each unit container shall be packaged in an outer container. This outer container shall be designed so as to protect
the inner container from damage due to storage.
4.7.3 Shipping container
Each unit container, or a number of unit containers not necessarily of the same type, may be packaged in a
shipping container designed to protect the contents under normal conditions of handling, transit, and storage.
4.8 Marking
4.8.1 Container label
Each prosthesis shall be accompanied by a label(s) on an appropriate container(s). At least the following
information shall be provided on the label(s):
a) name, address, and/or trademark of the manufacturer;
b) the material of construction and type of construction (see 4.3);
NOTE  The intention of clause references is to assist in adequately describing the device. It is not necessary to be redundant
(e.g. porcine xenograft, synthetic polyester).
c) the configuration (see 4.1). A symbol may be substituted for a written description of the prosthesis (e.g.  œ =
−
straight,  I = bifurcated,  = axillo-bifemoral);
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d) the nominal usable length (see 5.4);
e) the nominal relaxed internal diameter(s) (see 5.5);
f) if appropriate, the nominal pressurized internal diameter(s) (see 5.6);
g) if appropriate, porosity, mean water permeability, integral water permeability/leakage, and/or water entry
pressure (see 5.2);
h) the words STERILE DO NOT RESTERILIZE SINGLE USE ONLY, or equivalent phrase or symbols, in
prominent form, if applicable (see 4.5);
i) manufacturer's batch or lot number;
j) sterile lot number;
NOTE  If the manufacturer's batch or lot number (i) and the sterile lot number (j) can be traced to the same information, only
one number need be given.
k) date of sterilization and/or the expiry/expiration date;
l) for prostheses supplied sterile, a warning against the use of the device if the package is open or damaged;
m) manufacturer's recommendations for storage, when applicable;
n) the chemical nature of any storage fluid in the unit container, with any appropriate hazard warning;
o) if appropriate, a prominent statement regarding preclotting requirements or restrictions.
4.8.2 Record label
Each prosthesis shall be supplied with at least three adhesive record labels suitable for attachment to the records of
the patient receiving the implant. The record label shall include the following information:
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a) manufacturer's name and address;
b) product name;
c) manufacturer's batch and/or sterile lot number;
d) part or model number (manufacturer's catalog number).
4.9 Test reports
NOTE  With some tests, reports may not be required.
4.9.1 General
When requested, test methods and results shall be disclosed in the form of a test report.
A test report shall provide at least the following information:
a) manufacturer's or distributor's name;
b) location and date of test;
c) batch and/or lot number(s);
d) manufacturer's or distributor's specifications;
e) test results;
f) statement of compliance or noncompliance with the test methods specified in the appropriate clause of this
International Standard.
NOTE  For the purposes of this International Standard, the unit grams is sometimes used as a representation of force, even
though it is recognized that grams is a unit of mass.
4.9.2 Additional information
In addition to the test report, the following information shall be recorded:
a) material(s) of manufacture, in accordance with 4.3;
b) the configuration and type of construction of the prosthesis;
c) the dimensions of the prosthesis in accordance with 4.1, 4.1.2, 4.1.3, 4.1.4;
d) a statement indicating whether each sample prosthesis has or has not been sterilized and, if appropriate, the
method of sterilization used;
e) the test method(s) in accordance with the appropriate clauses in this International Standard;
f) the atmosphere, including mean and tolerance for controlled environments, in which the prosthesis was
conditioned and/or tested;
g) the number of samples and the observations per sample;
h) the minimum and maximum values observed.
5 Requirements for finished prosthesis
NOTE  Suggestions concerning appropriate tests for characterization, quality control testing and 100 % inspections may be
found in Table 1.
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Table 1 — Suggested appropriate tests
TEST CHARACTERIZATION QC TESTING 100% INSPECTIONS
Surface properties x x
Porosity
Water permeability Select Select
Integral water permeability appropriate appropriate
Leakage test(s) test(s)
Water entry pressure
Strength after repeated puncture x
Tensile strength x Select appropriate Select
Bursting strength x test(s) appropriate
Usable length x x test(s)
Relaxed inner diameter x x
Pressurized inner diameter x
Wall thickness x
Suture retention strength x
Kink resistance x
All testing may not be appropriate for all prosthesis designs. See NOTE in clause 8.
Justification shall be provided for the properties not measured for characterization.
It is impossible, at publication of this International Standard, to take into consideration all future and emerging
technologies. These emerging-technology prostheses will need to follow the basic test protocols of this International
Standard to characterize the device. Testing beyond the scope of this International Standard may also be
necessary to characterize new emerging technology prostheses. Consideration shall be given to the failure modes
of the prostheses and their effects on the performance of the device in identifying the appropriate testing. For
compound prostheses, although it may be appropriate to conduct some of the testing described in this International
Standard on components of the prosthesis, testing of the device as a whole is also required. In addition, if the
compound prosthesis is partially constructed of a resorbable component, the nonresorbable portion of the device
shall be characterized as well as the device as a whole.
Each segment of a composite prosthesis shall be tested. In addition, any manufactured anastomosis shall satisfy
the requirements of this International Standard relating to leakage (5.2.3) and factory anastomotic strength (either
8.3.2 or 8.3.3.3).
Retesting shall be performed whenever significant changes are made in materials, construction, configuration,
application or processing methods.
The test methods in this International Standard shall be used unless the design of the prosthesis is such that
alternative methods must be employed. An alternative method shall be validated and disclosed by the manufacturer
of the prosthesis with a justification for the method selected.
5.1 Visual inspection
The prosthesis shall show no discontinuities in construction, and shall show no dirt, soiled areas, spots, stains,
loose particles or other defects that would render the prosthesis unsuitable for its intended use.
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Testing shall be performed in accordance with 8.1.
5.2 Porosity, water permeability, integral water permeability/leakage, and water entry pressure
Porosity, water permeability, integral water permeability/leakage, and/or water entry pressure shall be evaluated as
appropriate to the device. Justification shall be provided for the property(ies) selected to be measured.
5.2.1 Porosity
The mean porosity of the sample prosthesis shall be measured using one of the methods given in 8.2.1.
The mean porosity of the sample prosthesis shall be within the nominal range declared by the manufacturer.
5.2.2 Water permeability
The mean water permeability of the sample prosthesis shall be measured using the method given in 8.2.2.
NOTE  When applicable, the manufacturer shall provide recommendations whereby the water permeability can be reduced by
preclotting.
The water permeability of the sample prosthesis shall be less than the maximum, or within the tolerance, of the
nominal water permeability disclosed by the manufacturer.
5.2.3 Integral water permeability/leakage
The mean integral water permeability/leakage and/or the anastomotic leakage of the sample prosthesis shall be
measured using the method given in 8.2.3.
The integral water permeability/leakage of the sample prosthesis shall be less than the maximum disclosed by the
manufacturer.
5.2.4 Water entry pressure
The mean water entry pressure of the sample prosthesis shall be measured using the method given in 8.2.4.
The water entry pressure of the sample prosthesis shall be greater than the minimum or within the tolerance
disclosed by the manufacturer.
5.3 Strength
The sample prosthesis shall be tested for longitudinal tensile strength in accordance with 8.3.2, for burst strength in
accordance with 8.3.3 and factory anastomotic strength in accordance with either 8.3.2 or 8.3.3.3, if applicable.
Circumferential tensile strength (see 8.3.1) is only required if burst strength cannot be readily measured.
The value of tensile strength, burst strength and factory anastomotic strength shall be greater than the minimum
values disclosed by the manufacturer.
NOTE  Although the test methods given in 8.3.3.1 and 8.3.3.2 may be of equal validity for quality assurance purposes, they
are not necessarily equivalent. There are markedly different stress/strain relationships between uniaxial and biaxial stressing
for many prostheses.
For vascular prostheses with a designated intended clinical use for vascular access, the strength after repeated
puncture shall be measured. The measured value for the strength after repeated puncture of the sample prosthesis
shall be disclosed by the manufacturer.
Testing for strength after repeated puncture shall be performed in accordance with 8.3.4, which shall be disclosed
on demand by the manufacturer of the prosthesis with a justification for the method selected.
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5.4 Length
The usable length shall be measured and disclosed. The usable length of the prosthesis shall be no less than that
declared by the manufacturer.
Testing shall be performed in accordance with 8.4.
5.5 Relaxed internal diameter
The specified limits for acceptance shall be as follows:
a) For prostheses of nominal relaxed internal diameter of 10 mm or less, the measured relaxed internal diameter
shall equal the nominal relaxed internal diameter disclosed by the manufacturer, within a tolerance of ± 0,5 mm.
b) For prostheses of nominal relaxed internal diameter of 20 mm or less but greater than 10 mm, the measured
relaxed internal diameter shall equal the nominal relaxed internal diameter disclosed by the manufacturer,
within a tolerance of ± 1,0 mm.
c) For prostheses of nominal relaxed internal diameter greater than 20 mm, the measured relaxed internal
diameter of the sample prosthesis shall equal the nominal relaxed internal diameter declared by the
manufacturer, within a tolerance of ± 5 %.
Alternative limits for acceptance shall be justified.
Testing shall be performed in accordance with 8.5, which shall be disclosed on demand by the manufacturer of the
prosthesis with a justification for the method selected.
5.6 Pressurized internal diameter
If the pressurized internal diameter exceeds the nominal relaxed internal diameter declared by the manufacturer by
more than 10 %, the nominal pressurized internal diameter shall be declared by the manufacturer [see 4.8.1f)].
Testing shall be performed in accordance with 8.6.
5.7 Wall thickness
The wall thickness shall be measured in accordance with 8.7.
The wall thickness shall be within the tolerance as specified by the manufacturer.
5.8 Suture retention strength
The suture retention strength shall be measured in accordance with 8.8.
The suture retention strength shall be greater than the minimum disclosed by the manufacturer.
5.9 Kink diameter/radius
The kink diameter/radius of vascular prostheses shall be measured and disclosed by the manufacturer.
Testing shall be performed in accordance with 8.9.
NOTE  This test may not be applicable to all vascular prostheses (e.g. crimped textile prostheses).
5.10 Compliance
Compliance shall be measured and disclosed as appropriate to the device and in accordance with 8.10.
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6 Requirements for in vivo preclinical and clinical evaluation
In vivo preclinical and clinical evaluation may be necessary when safety and efficacy, or substantial equivalence,
cannot be demonstrated solely through in vitro testing.
NOTE  Innovative products and/or products with specific claims, including a new clinical application, may require further
testing, including a failure mode analysis and design assessment.
6.1 In vivo preclinical testing
The purpose of in vivo preclinical testing is to assess the short-term response and patency of the prosthesis, the
response of the host tissues following implantation in a vascular site, and any gross alteration in the physical,
chemical and biological properties of the material(s) of construction, including any coatings, where appropriate. This
testing is not intended to demonstrate the long-term performance of the prosthesis.
Each type of prosthesis be tested by implantation at the intended, or at an analogous, vascular site in at least six
animals for at least 20 weeks in each animal unless a justification for a shorter term study is provided. Appropriate
controlled in vivo preclinical studies shall be used to collect comparable information, unless the absence of a control
group is justified. The duration of patency for each prosthesis shall be monitored by appropriate periodic
examination (e.g. angiography, Doppler) and the results recorded. Loss of patency before the intended study
duration does not necessarily exclude the animal from the study population used to assess prosthetic function and
host tissue response. All animals implanted with either test or control prostheses, including those excluded from the
final analysis, shall be recorded and reported.
A prosthesis shall not be tested in a species from which it was derived unless justification is provided.
The prosthesis shall be shown to be suitable for its intended use, based on the objectives declared and justified in
the in vivo preclinical testing protocol (see 9.1.2).
Testing shall be performed in accordance with 9.1, or by a validated alternative test method, which shall be
disclosed by the manufacturer of the prosthesis. The design of in vivo preclinical testing shall be justified: in
particular, the experimental protocol, measurement methods, and data analysis. Consideration shall be given to the
objectives of the study in this justification.
6.2 Clinical evaluation
The purpose of clinical evaluation is to assess the short-term (minimum 1 year) safety and efficacy of a vascular
prosthesis for a particular clinical application. This evaluation is not intended to demonstrate the long-term
performance of the prosthesis.
An investigation shall be carried out for each new prosthesis or new clinical application of a prosthesis prior to
general marketing, using the principles given in ISO 14155 or an equivalent publication. The prosthesis shall have
satisfied all appropriate requirements of clauses 4 and 5 and 6.1 of this International Standard before starting
clinical evaluation.
NOTE 1  Clinical evaluation conducted in the thoracic aortic implant site may be used to support straight abdominal aortic
applications.
The clinical evaluation shall be conducted at a minimum of three institutions, each of which shall implant a minimum
of 10 of the prostheses. The smallest diameter of a prosthesis, with a representative sample of all other diameters
to be marketed for the particular clinical application, shall be included in the clinical evaluation (see NOTES).
For a prosthesis that is infrequently used, a clinical evaluation using an appropriate smaller number of patients shall
be conducted at a minimum of three institutions. A justification of the numbers studied shall be provided.
NOTE 2  Additions of diameters to a marketed prosthesis for the same clinical application may require further clinical
evaluation.
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NOTE 3  For a compound prosthesis constructed of a biological resorbable component and a currently marketed substrate
(e.g. knitted or woven fabric), the smallest diameter of the prosthesis is not required to be included in the clinical evaluation,
provided that this diameter of the substrate is marketed.
The clinical evaluation shall be continued for a minimum of 12 months in each patient. Loss of patency before the
intended study duration does not necessarily exclude the patient from the study population used to assess
prosthetic function. All patients implanted with either test or control prostheses, including those excluded from the
final analysis, shall be recorded and reported.
NOTE 4  It is advisable to continue the follow up until at least 24 months after the last prosthesis has been implanted.
NOTE 5  For a new prosthesis constructed of a biologic resorbable component used in a currently marketed prosthesis and a
different currently marketed substrate, a 6-month study duration may be appropriate.
Objective evidence of safety and efficacy shall be provided. This evidence shall be compared to data collected and
analyzed in an equivalent manner from patients managed by currently accepted medical and/or surgical treatment
(control group). Justification shall be provided for the choice of control group, measurement methods, and statistical
analyses employed.
The clinical data shall be collected, analyzed, and recorded in accordance with 9.2, or by a validated alternative test
method, which shall be disclosed by the manufacturer of the prosthesis on demand.
The design of the clinical evaluation shall be justified: the total number of recipients of the prosthesis, the protocol,
measurement methods, and data analysis being justified according to appropriate statistical methods. Consideration
shall be given to the objectives of the study in this justification.
7 Sampling
During development, a sampling plan should be utilized which will ensure that an adequate representation of the
data has been obtained for each parameter under evaluation.
7.1 Sampling for characterization
The design characteristics of the vascular prostheses must be verified to be representative of the devices to be
released for distribution. For characterization a minimum of three random samples from each of three random
batches or lots shall be used.
7.2 Sampling for quality control
7.2.1 Random sampling
Where a prosthesis is manufactured by a discontinuous or individual process (i.e. where the process is of a lot or
batch type), then random samples shall be taken from each lot or batch.
7.2.2 Time interval sampling
Where a prosthesis is manufactured by a continuous process, the batch may be designated by an elapsed period of
production, when samples shall be taken at fixed time intervals during the production run.
7.2.3 Number of samples
The number of samples taken for a test shall be in accordance with ISO 2859-1 and ISO 2859-2 having regard to a
declared AOQL (Average Outgoing Quality Limit) and the number of items in the lot or batch. (see NOTES).
NOTE 1  Alternatively, it may be preferable to use AQL (Acceptance Quality Level) in place of AOQL.
NOTE 2  The number of samples may alternatively be determined by the manufacturer if the sampling plan is based on a
validated process with historical data showing the validity of their alternate sampling plan.
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8 Test methods for vascular prostheses
NOTE 1  Each test method may not be appropriate for all prosthesis designs. The codes given below will give guidance as to
which test methods may be appropriate:
A All type prostheses
B Biological
C Coated
N Synthetic nontextile
T Synthetic textile
NOTE 2  Compound or composite prostheses may encompass one or more of the above categories.
8.1 Visual inspection (A)
8.1.1 Principle
The prosthesis is examined visually for defects.
8.1.2 Apparatus
Apparatus to be used include:
a) a controlled air environment, e.g. a cleanroom or cabinet;
b) a source of diffuse back-illumination, and/or direct illumination.
8.1.3 Sampling
Sampling shall be 100 %.
8.1.4 Test procedure
Examine the prosthesis by unmagnified, corrected vision under illumination for the presence of holes and other
discontinuities or imperfections of fabrication, and for the presence of dirt, soiled areas, spots, stains, loose
particles, or other defects that would render the prosthesis unsuitable for its intended use.
8.1.5 Expression of results
The number of units accepted and rejected shall be recorded.
8.1.6 Test reports and additional information
A test report is not normally required (see NOTE in 4.9).
8.2 Determination of porosity, water permeability, integral water permeability/leakage, and water
entry pressure
8.2.1 Determination of porosity (N)
One of the following methods shall be used:
a) planimetric porosity;
b) gravimetric porosity;
c) microscopic porosity.
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NOTE  The planimetric and gravimetric methods provide a direct measurement of porosity, while the microscopic method
provides an index of porosity in terms of internodal distance or mean pore diameter.
An alternative method may be used provided that there is documented evidence that it is equivalent.
8.2.1.1 Planimetric determination of porosity
8.2.1.1.1 Principle
This test is intended to determine the area of the voids and/or the area of the material on the sample prosthesis by
means of measurements made on a scanning electron micrograph or optical micrograph. If there is a difference
between the inner and outer surface, both should be characterized unless justification is provided for the surface
measured.
8.2.1.1.2 Apparatus
Apparatus to be used include:
a) equipment for preparing a scanning electron micrograph of a section of the prosthesis, or equipment to enable
visual examination and/or photography of the specimen or a section of the specimen by light microscopy;
b) a device such as a microplanimeter, micrometer, or computer digitizing table capable of measuring to an
accuracy of ± 1% of the manufacturer's declared mean pore diameter or internodal distance.
8.2.1.1.3 Sampling
Sampling shall be in accordance with clause 7.
8.2.1.1.4 Test procedure
From each sample prosthesis, either:
a) prepare a scanning electron micrograph(s);
b) prepare a photograph(s) for optical examination of the surface of the sample (see NOTE). The surface
examined (inner or outer) shall be recorded.
NOTE  The degr
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