ISO 41064:2023

INTERNATIONAL ISO
STANDARD 41064
First edition
2023-06
Health informatics — Standard
communication protocol — Computer-
assisted electrocardiography
Informatique de santé — Protocole de communication standard —
Électrocardiographie assistée par ordinateur
Reference number
ISO 41064:2023(E)
© ISO 2023

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ISO 41064:2023(E)
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© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii
  © ISO 2023 – All rights reserved

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ISO 41064:2023(E)
Contents Page
Foreword . iv
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
5 Definition of the data contents and format . 4
5.1 General considerations . 4
5.2 Specifications for the data structure . 5
5.3 Pointer section – Section 0 . 10
5.4 Header information - Patient data / ECG metadata – Section 1 . 12
5.5 Huffman tables – Section 2 . 28
5.6 ECG leads definition – Section 3 . 30
5.7 Reserved for legacy SCP-ECG versions – Section 4 . 39
5.8 Encoded type 0 reference beat data – Section 5 . 41
5.9 Short-term ECG Rhythm data – Section 6 . 44
5.10 Global ECG measurements – Section 7 . 46
5.11 Storage of full text interpretive statements – Section 8 . 60
5.12 Storage of manufacturer specific interpretive statements and data related to the
overreading trail – Section 9 . 61
5.13 Per-lead ECG measurements – Section 10 . 61
5.14 Storage of the universal ECG interpretive statement codes – Section 11 . 70
5.15 Long-term ECG rhythm data – Section 12 . 74
5.16 Stress tests, Drug trials and Protocol based ECG recordings Metadata – Section 13 . 79
5.17 Selected ECG Sequences Repository – Section 14 . 90
5.18 Beat-by-Beat ECG measurements and annotations – Section 15 . 94
5.19 Selected ECG beats measurements and annotations – Section 16 . 109
5.20 Pacemaker Spikes measurements and annotations – Section 17 . 118
5.21 Additional ECG annotations – Section 18 . 132
Annex A (normative) Supplementary information and additional encoding specifications . 139
Annex B (informative)  Universal ECG interpretation statements codes . 147
Annex C (informative) Definition of compliance with the SCP ECG standard . 173
Annex D (Informative) Methodology of the recommended ECG signal compression
technique . 182
Annex E (informative) Cross-references to other ECG standards . 217
Annex F (informative) Implementation Recommendations . 220
Annex G (informative) Glossary . 222
Annex H (informative) Revision History . 224
Bibliography . 227

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ISO 41064:2023(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of
(a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by the European Committee for Standardization (CEN) (as EN 1064:2020)
and was adopted, without modification other than those given below by Technical Committee
ISO/TC 215, Health informatics.
— changed "this Standard" or "this technical specification" to "this document" and "the present
standard" or "this version of the standard" to respectively "the present document" or "this version of
the document";
— changed any "EN ISO xxxx" references to "ISO xxxx" references;
— changed "section" to "clause" in 5.13.6, NOTE 10 and in Clause E.2;
— fixed the corrupted characters in the formula in D.4.8.10;
— corrected the wording in Table 8.
This first edition of ISO 41064 cancels and replaces ISO 11073-91064:2009, which has been technically
revised.
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ISO 41064:2023(E)
The main changes are as follows:
— Deprecated the possibility to use other than UTF-8 language encoding schemes and deprecated
former Annex A: Encoding of alphanumeric ECG data in a multilingual environment. Now only UTF-
8 encoded text strings are allowed;
— Deprecated the use of beat subtraction and bimodal compression schemes which are no longer
supported. But Section 4, formerly used to store QRS locations to allow beat subtraction for
computing a “residual signal”, is still mentioned in the present document to support decoding and
conversion of legacy SCP-ECG version 1.x and 2.x files into SCP-ECG version V3.0 files;
— Significantly extended the global and per-lead measurements sections. The terminology used
and the measurements and annotations provided have been harmonized with ISO/IEEE 11073-
10102 Annotated ECG (aECG) and 11073-10101 Nomenclature (Vital signs) standards and with the
different recommendations and consensus papers found in the scientific literature;
— Extended Section 11 to include two new ECG interpretation and overreading data coding
schemes, based on the categorized AHA statement codes and according to the CDISC (Controlled
Terminology. Clinical Data Interchange Standards Consortium) code;
— Introduced Sections 12 to 14 to provide means of storing long-term ECG rhythm data and
protocol-based ECG recordings, e.g. stress tests and drug trials procedures;
— Introduced Sections 15 to 17 to allow the storage of different sets of per-lead beat or spike
measurements and annotations;
— Introduced Section 18 “Additional ECG annotations” to provide a solution for storing any type
of manually or automatically produced annotation which has not been stored in a systematic way in
sections 7, 8, 10, 11 and 15 to 17;
— More details on the main changes can be found hereafter at the end of the Introduction and in
Annex H, Revision History.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

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ISO 41064:2023(E)
Introduction
The electrocardiogram (ECG) is a recording of voltage changes transmitted to the body surface by
electrical events in the heart muscle, providing direct evidence of cardiac rhythm and conduction, and
indirect evidence of certain aspects of myocardial anatomy, blood supply and function. During its
propagation to the surface, extracardiac tissues may intervene and influence the ECG morphology.
Electrocardiography has been used for many years, and is increasingly used as a key, non-invasive and
low cost method in the diagnosis and early detection of coronary heart disease, which is the leading
1
cause of mortality worldwide [56] . Of the 56,9 million global deaths in 2016, 40,5 million (71,3 %)
were due to non-communicable diseases (NCDs) and 17,9 million (31 %) were due to cardiovascular
diseases (CVDs). Out of these 17,9 million cardiovascular deaths, ischaemic heart disease was
responsible for 9,4 million and strokes were responsible for 5,8 million deaths. More than 3 million of
these 17,9 million CVD deaths occurred before the age of 60. The percentage of premature deaths from
CVDs ranges from 8,8 % in high-income countries to 26 % in low-income countries [56].
In 2018, it was estimated that, worldwide, approximatively 3 million ECGs are recorded every day [41].
The Mayo Clinic, for example, nowadays performs about 240 000 standard ECG recordings per year
[57]. According to Research And Markets, the Global Electrocardiography Devices (ECG) Market
accounted for $5 122 million in 2018 and is expected to reach $9 738 million by 2027 [58]. The factors
driving this market include the increasing geriatric population, rising incidences of lifestyle diseases,
technological advancements in diagnostic ECG devices, and high growth rate in developing countries.
Almost all newer electrocardiographs nowadays use digital recording, interpretation and
communication techniques, and there is an increasing number of portable and even wearable (mobile)
ECG devices that are now used instead of the traditional ECG cart. These stand-alone, microprocessor
based machines and devices can be connected to each other, to a host computer, to the internet or to a
hospital information system for reporting, long-term storage in the Medical Electronic Record and serial
comparison. To this end, various manufacturers have used different techniques.
It is in the general public interest for users not to be restricted in their options by incompatible
technical features and services of different systems and devices. ECG processing is increasingly being
integrated with various other types of data processing in health care. This evolution will have
considerable impact on the storage and communication of ECG data. There are many different end-
users who for different purposes (support of patient care, management, drug trials and/or drug
management, research and education) want to obtain a copy of the signal data, of the interpretive
report and/or measurement results. Being one of the very first ever developed systems for medical
decision support, computerized ECG interpretation stretches from departments of cardiology in
hospitals, to general practitioners in primary care and health care centres and to home care. In life-
threatening acute myocardial infarction, ECGs are now used in ambulances by paramedical personnel to
assess the necessity for administering thrombolytic agents or to alert cathlabs to prepare for a coronary
intervention, with long-distance monitoring whenever possible, and in self-care situations to detect
ischemia or life threatening arrhythmias as early as possible [31].
To facilitate the exchange of information between various systems, it was of utmost importance that a
standard communications protocol for computer-aided electrocardiography (SCP-ECG) was established,
as defined in this document. Its aim is to specify a data format for transferring ECG signals, metadata
and reports from any vendor's computerized ECG device to any other's vendor central ECG
management system. The same standard should also allow standardized transfer of digitised ECG data

1
Figures in square brackets refer to the Bibliography.
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ISO 41064:2023(E)
and results between various computer and information systems, Electronic Medical Records, and ECG
data repositories.
Under this standard communications protocol (SCP-ECG), the contents and format of the ECG waveform
data, metadata and the measurements from ECG devices of different manufacturers are not expected to
be identical. As a result, the determination of the suitability of a device and/or system for any particular
application remains with the user/purchaser. The following possible uses of ECG records require
special attention:
— serial comparison of ECGs and interpretations;
— printout formats of ECGs;
— maintaining an audit trail of edits and annotations;
— integration into an electronic medical record;
— integration into clinical information systems and data repositories.
The users are cautioned to make sure that the data contents and format of the waveform data,
metadata, measurements, and the interpretive statements meet their specific needs. If more than one
type of ECG device and/or ECG management system is interconnected, the user is also advised to verify
with the manufacturers that the data from different systems and devices are compatible with each other
and with the user’s needs.
In order to understand this document, the reader needs some basic knowledge of electrocardiology,
electrocardiography and signal processing.
This document not only relates to the conventional recording of the electrocardiogram, i.e. the so-called
standard 12-lead electrocardiogram and the vectorcardiogram (VCG), but also to other types of ECG
such as Holter ECG, physiologic monitoring ECG, stress ECG, intracardiac ECG, home care ECG
monitoring and wearable self-care ECG devices. Initially, the electric connections used for recording the
ECG were made to the limbs only. These connections to the right arm (RA), left arm (LA) and left leg
(LL) were introduced by Einthoven. The electrical variations detected by these electrode connections
are algebraically combined to form the bipolar leads I, II, and III. Lead I, for example records the
difference between the voltages of the electrodes placed on the left arm and the right arm. The unipolar
electrocardiographic leads (VR, VL, VF and the precordial leads V1 to V6) were introduced much later,
starting in 1933. In these leads, potentials are recorded at one location with respect to a level which
does not vary significantly in electrical activity during cardiac contraction. The “augmented” limb lead
potentials (aVR, aVL, aVF) are recorded with reference to the average potential of (L+F), (R+F) and
(L+R) respectively, where R, L and F refer to the RA, LA and LL electrodes. The unipolar chest leads are
recorded with reference to the average potential of (RA+RL+LL)/3 which is called the Wilson “central
terminal” (CT). In vectorcardiography, recordings are made from three mutually orthogonal leads,
running parallel to one of the rectilinear coordinate axes of the body. The axes are the X-axis going right
to left, the Y-axis with a top to bottom orientation, and the Z or front to back axis. In 12-Lead stress ECG
recordings, the limb electrodes are placed on the torso to reduce limb movement artefacts. The same
electrode positions apply to some Holter, emergency and home care recordings, both to limit movement
artefacts and undressing.
In some research centres, so-called body surface maps are obtained by placing many (from 24 to 124 or
even more) closely spaced electrodes around the torso. This document has not been designed to handle
exchange of such recordings, although future extensions could be made to this end. The standard has
also not been designed to exchange specialized recordings of intracardiac potentials (electrograms)
recorded in the EP (Electrophysiology) laboratories or by cardiac implantable electronic devices (CIED),
viz pacemakers, implantable cardioverter-defibrillators (ICDs) and cardiac resynchronization therapy
(CRT) devices, although it could also be used to this intent.
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ISO 41064:2023(E)
ECG computer processing can be reduced to 3 principal stages:
1) data acquisition, encoding, transmission and storage;
2) pattern recognition and feature extraction, i.e. ECG measurement;
3) diagnostic classification.
In each of these stages there are important needs for standardization and quality assurance testing. The
scope of this document is confined to the first of these three stages. Quality assurance of ECG
measurement and diagnostic classification have been addressed by the CSE Working Party (see [32]
2
and [44] to [50]) and to some extent by IEC 60601-2-25:2011 [4]. The latter also addresses the issue of
quality assurance testing of the signal acquisition hardware and filtering.
The various data sections that can be transmitted by means of the standard ECG communications
protocol are defined in Clause 5 of this document.
The selection and definition of ECG specific high-level syntaxes and query languages for transfer of
messages and data between devices or between devices and hosts or host-to-hosts, using for example
Bluetooth, TCP/IP, FTP, USB, Filesystem, HL7, etc., are beyond the scope of this document.
The main goal of the SCP-ECG standard is to address ECG data and related metadata structuring,
semantics and syntax, with the objective of facilitating interoperability and thus to support and
promote the exchange of the relevant information for ECG diagnosis. Indeed, as recommended by the
ACC/AHA/ACP-ASIM task force: “Electrocardiogram readers should understand the importance of
comparing a current tracing to previous tracings in order to make correct diagnoses. All abnormal
tracings should be compared with available previous tracings. The accuracy of some diagnoses may be
considerably enhanced by reviewing previous tracings.” [33]. It is thus of utmost importance to provide
a storage format enabling any device or computer program performing the analysis and interpretation
of a current ECG to perform a reliable re-analysis of the previous ECGs. For assessing serial changes
between ECG measurements it is necessary that the measurements are computed in the same way on
each recording in order to avoid any bias.
The binary encoding of ECG data within SCP-ECG and the included content self-control capabilities
allow for an efficient encoding, an encapsulation of all ECG-related parameters, and a small memory
footprint compliant with mHealth scenarios for an early detection of cardiac diseases, anywhere and
anytime [31], [39]. These features not only provide an advantage in data transmission and archiving,
but also when the data need to be encrypted (for protecting the data and the confidentiality), or signed
(protection against changes).
The present version of the SCP-ECG standard has been significantly amended, with the objective to
provide means to support the storage and interchange of almost all existing ECG recording modalities,
processing results, annotations and diagnoses, as well as precisely defined metadata enabling the
harmonization with other standards in health informatics. The main changes are summarized hereafter.
The ECG data and related metadata addressed in this document are now structured into 18 sections.
Sections 0 to 11 already existed in the previous versions of SCP-ECG and, although they have been
significantly updated, they remain almost backwards compatible with SCP-ECG V1.x and V2.x, except for
other than UTF-8 text strings encoding and beat subtraction or bimodal compression schemes which
are no longer supported. Starting with SCP-ECG V3.0, only lossless compression (difference and
Huffman encoding) of the long-term rhythm data (section 6) and of the reference beat type 0 data
(section 5) are now allowed. In addition, to simplify encoding, the present document recommends to
store all ECG signal data uncompressed as a series of fixed length, signed integers and to reserve

2 Impacted by IEC/CD 80601-2-86 under development
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ISO 41064:2023(E)
difference data calculation and Huffman encoding for mobile and/or wearable devices, when they are
intended to be used in poorly served areas with limited wireless connectivity such as GPRS, where
significant lossless data reduction strategies are still of importance. Converting legacy SCP-ECG V1.x and
V2.x files into SCP-ECG V3.0 compliant files would thus only require to convert non UTF-8 text strings
into UTF-8 and to store ECG signal data, if any, uncompressed. Sections 12 to 18, which are new, have
been introduced to support the storage of continuous, long-term ECG recordings, of selected sequences
of stress tests, drug trials and protocol-based ECG recordings, and the related metadata, measurements
and annotations
All over the document, emphasis has been put on cross-referencing and providing a semantic mapping
between the terminology and the methodologies used in SCP-ECG and the ISO/IEEE 11073-10102
Annotated ECG (aECG) [9] and 11073-10101 Nomenclature (Vital signs) [8] standards and on levering
the ambiguities and inaccuracies of some of these other than SCP-ECG standards.
In section 1, SCP-ECG Drugs coding (Tag 10), Medical History codes (Tag 32) and Electrode
configuration Codes (Tag 33) have been significantly updated to take account of the evolution of the
medical needs, and two new tags have been introduced, respectively aimed at describing Implanted
Cardiac Devices (Tag 36, based on the NASPE/BPEG coding systems [28], [29]) and at specifying drugs
according to the WHO Anatomical Therapeutic Chemical Classification System (ATC code [43], Tag 37).
Section 4, formerly used to store QRS locations to allow beat subtraction for computing a “residual
signal”, has been deprecated. But Section 4 is still mentioned in the present document to support
decoding and conversion of legacy SCP-ECG version 1.x and 2.x files into SCP-ECG version V3.0 files.
The global and per-lead measurements sections have been significantly extended. The terminology used
and the measurements and annotations provided have been harmonized with the aECG standard [9]
and with the different recommendations and consensus papers (viz the need for introducing new
measurements describing the early repolarization patterns) found in the scientific literature.
All measurements have been precisely defined, with the aim of unifying the way ECG measurements are
performed and of serving as a reference for scientific work. Manufacturers using methods other than
those recommended in SCP-ECG Version 3.0 are requested to specify the method they are using in the
physician's guide.
Section 11, which aims to contain the most recent interpretation and overreading data, now allows
three different coding schemes (in addition to free text): (1) according to the Universal Statement Codes
and Coding Rules defined in Annex B: (2) based on the categorized AHA statement codes [21]; (3)
according to the CDISC (Controlled Terminology. Clinical Data Interchange Standards Consortium) code
[30].
The three different coding schemes may coexist, i.e. an interpretive statement encoded according to the
SCP-ECG Universal Statement Codes and Coding Rules may concomitantly also be encoded according to
the AHA and/or the CDISC code specifications.
Emphasis has also been put on extending and harmonizing the SCP-ECG Universal Statement Codes
defined in Annex A with the AHA and CDISC statement codes and specifications, and with aECG [9] and
DICOM [19].
Starting with version V3.0, in addition to the short duration resting ECG (section 6) and the
corresponding type 0 reference beat (section 5), the standard now provides means of storing long-term
ECG rhythm data in section 12, e.g. up to 40 days continuous recording of 3-Lead ECG signals sampled at
200 samples/sec with a 16 bit resolution, in section 14 several selected short to medium duration ECG
sequences, and, in section 13, the related metadata and reference beats (or pointers to selected
reference beats). These two additional sections have been included to support protocol-based ECG
recordings, viz stress tests and drug trials procedures.
The format of section 12 is very similar to the ISHNE format [26]. In order to preserve random access to
the record’s segments, no compression or encoding is allowed in this section.
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ISO 41064:2023(E)
In addition to the full set of global measurements (section 7) and the per-lead measurements (section
10) of the type 0 reference beat, starting with version V3.0 the standard now allows the storage, in
section 15, of several pre-defined global and per-lead beat measurements and annotations, for all or for
only some computed or selected beats of the analysed signals (long-term and/or long-term ECGs stored
in sections 12 and 14 and/or in section 6). The beats may have been selected one by one by a physician
or by a beat typing algorithm (reference beats of different types, etc.), or may refer to the entire set of
beats from one or more selected time windows within the long-term ECG stored in section 12 or in the
long-term ECGs stored in sections 6 or 14.
In another scenario, one may choose to select and store the measurements and annotations for K
preselected, not necessarily consecutive beats, in as much Measurement Blocks (MB) as there are
selected beats, for thorough QT studies for example. To facilitate comparison with reference beats
...