ISO/PAS 7020:2023

PUBLICLY ISO/PAS
AVAILABLE 7020
SPECIFICATION
First edition
2023-05
Sizing parameters of surgical valve
prostheses: Requirements regarding
the application of ISO 5840-2
Désignation des dimensions des prothèses valvulaires chirurgicales:
Exigences relatives à l'application de l'ISO 5840-2
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 4
5 Information required for the outer container labelling . 4
5.1 General . 4
5.2 Intended valve to be replaced . 5
5.3 Inflow orifice diameter . 5
5.3.1 General . 5
5.3.2 Mechanical valves . 5
5.3.3 Stented bioprosthetic valves . 6
5.4 Effective orifice diameter . 7
5.4.1 General . 7
5.4.2 Steady flow method . 7
5.5 Valve housing external diameter . 8
5.6 External sewing ring diameter . 9
6 Labelling format .9
Bibliography .10
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 150, Implants for surgery, Subcommittee
SC 2, Cardiovascular implants and extracorporeal systems.
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iv
Introduction
0.1 General
In the past, inconsistencies have been reported with the labelling and instructions for use associated
with sizing parameters and sizing procedures for surgical replacement heart valves, specifically,
mechanical and stented bioprosthetic valves. These inconsistencies have led to confusion among
some users about which size valve to implant in a particular patient and have also led to challenges in
comparing results (published or otherwise) from one valve model to another. A solution to the problem
can be achieved by providing more complete and accurate sizing information to the clinicians, which
will ultimately benefit the patients.
ISO 5840-2 identifies a number of sizing parameters that are required in the labelling (including on the
unit box, see ISO 5840-2:2021, 6.3.3, and instructions for use) to inform the selection of a surgical heart
valve prosthesis to be implanted in a specific patient. However, no guidance is offered in ISO 5840-2 on
how these parameters should be obtained.
0.2 Clinical rationale for additional sizing information
Successful valve replacement therapy requires that an adequate size surgical heart valve substitute is
used, based on patient body size and the native valve annulus size. An understanding of valve sizing
parameters and appropriate choice of size is critical to post-procedure success since a valve substitute
that is too small for the patient can result in prosthesis-patient mismatch. For aortic valve replacements,
[1]
severe mismatch has been reported in 5 % to 15 % of patients. Severe prosthesis-patient mismatch
leads to increased early, mid-term and late mortality, especially if the left ventricular ejection fraction
[2]-[5] [5]
(LVEF) is reduced. In the mid-term, it causes a higher incidence of heart failure and limits left
[5]
ventricular mass regression. In the long term, it can also contribute to accelerated structural valve
[6]
degeneration (SVD). Patients with severe prosthesis-patient mismatch can require replacement of
the valve substitute with another having a larger effective orifice area (EOA). However, re-intervention
has significant risk of mortality and morbidity.
The best approach to prosthesis-patient mismatch is prevention. This requires the surgeon to have
clear and accurate information about the sizing parameters and EOA of each valve substitute.
A surgical heart valve substitute is described by a labelled size given by the manufacturer, which is
assumed to be broadly consistent with the size of the patient native valve annulus for which the valve
[1]
is intended. Literature reviews and studies of haemodynamic function commonly compare valve
substitutes by labelled size, but there can be major differences between the patient native valve annulus
[8]-[11]
diameter and the labelled size of the valve substitute. Intraoperative sizing is further complicated
by the need for aortic supra-annular valves to fit within the aortic sinus. The disparity between labelled
size and actual size means that echocardiographic or clinical comparisons based on labelled size can be
misleading.
The issue of valve sizing is a complex problem and is being addressed in a stepwise fashion. The working
group revising ISO 5840-2 proposed a first step toward greater transparency by requiring additional
information be added to the unit box, namely, internal orifice diameter and effective orifice diameter.
Although this information does not necessarily inform the surgeon on whether the valve would fit in
the patient’s annulus, it helps to estimate the internal orifice available for blood flow and thus indirectly
the EOA. It is not feasible to use clinically measured EOA’s since sizing information must be available
before a surgical heart valve substitute is released for use in patients. Indeed, it can take a number of
years to gather sufficient echocardiographic data to confirm the clinical EOAs. Furthermore, the use
of echocardiographic data to help avoid prosthesis-patient mismatch has been criticized because of
[12]
variability in the measurements obtained in vivo. In vitro steady flow data have less variability and
allow meaningful comparison of every design and size of surgical heart valve substitute under the same
flow conditions. This information can be used by the surgeon to choose a specific valve substitute type
and size based on more standardized parameters than labelled valve size. It is anticipated that further
steps toward a standardised approach to sizing will be addressed in subsequent editions of ISO 5840-2.
v
This document provides further specifications to explain these two parameters (i.e. internal orifice
diameter and effective orifice diameter) and other sizing parameters. This document also guides the
manufacturer in selecting reproducible methods to obtain these parameters and the degree of accuracy
required.
vi
PUBLICLY AVAILABLE SPECIFICATION ISO/PAS 7020:2023(E)
Sizing parameters of surgical valve prostheses:
Requirements regarding the application of ISO 5840-2
1 Scope
This document describes in vitro methods of measurement of the sizing parameters for surgical valves
(referring to mechanical and stented bioprosthetic valves only here and hereafter). It represents a
consensus reached among manufacturers, independent bioengineers and clinicians, and is underpinned
by interlaboratory studies.
This document relates to surgical heart valve prostheses and is intended to be used in conjunction with
ISO 5840-1:2021 and ISO 5840-2:2021. Where noted, the requirements of this document clarify certain
requirements of ISO 5840-1 and/or ISO 5840-2. Specific methodologies are included for flexible leaflet
(bioprosthetic) and rigid (mechanical) valves. Sutureless valves, stentless valves and valved conduits
are not included.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 5840-1:2021, Cardiovascular implants — Cardiac valve prostheses — Part 1: General requirements
ISO 5840-2:2021, Cardiovascular implants — Cardiac valve prostheses — Part 2: Surgically implanted
heart valve substitutes
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
effective orifice area
EOA
A
eo
orifice area that has been derived from flow and pressure or velocity data
Note 1 to entry: For
...