Health informatics -- Medical waveform format

This document defines the application of Medical waveform Format Encoding Rules (MFER) to describe stress test electrocardiography, which is one of the outputs of exercise, pharmacological and cardiopulmonary stress test. MFER performed in physiological laboratories, healthcare clinics, etc. This document covers not only the electrocardiogram waveform but also the description of related stress information and biological signals, e.g. blood pressure, respiration gas, SpO2, etc..

Informatique de santé -- Format de la forme d'onde médicale

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Publication Date
03-Oct-2019
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6060 - International Standard published
Start Date
29-Aug-2019
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04-Oct-2019
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ISO/TS 22077-4:2019 - Health informatics -- Medical waveform format
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TECHNICAL ISO/TS
SPECIFICATION 22077-4
First edition
2019-10
Health informatics — Medical
waveform format —
Part 4:
Stress test electrocardiography
Reference number
ISO/TS 22077-4:2019(E)
ISO 2019
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ISO/TS 22077-4:2019(E)
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© ISO 2019

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ii © ISO 2019 – All rights reserved
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ISO/TS 22077-4:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms, definitions, symbols and abbreviations .................................................................................................................. 1

3.1 Terms and definitions ....................................................................................................................................................................... 1

3.2 Symbols and abbreviated terms............................................................................................................................................... 2

4 Outline of stress test cardiography rules .................................................................................................................................... 2

4.1 Configuration of waveform data (see Figure 1) .......................................................................................................... 2

4.2 Time synchronization (see Figure 2) ................................................................................................................................... 4

5 Waveform encoding ........................................................................................................................................................................................... 5

5.1 General ........................................................................................................................................................................................................... 5

5.1.1 Full disclosure waveform (see Figure 3) ..................................................................................................... 5

5.1.2 Intermittent record waveform (see Figure 4) ........................................................................................ 5

5.1.3 Abstract waveform (see Figure 5)..................................................................................................................... 6

5.2 Waveform class ....................................................................................................................................................................................... 7

5.2.1 General...................................................................................................................................................................................... 7

5.2.2 Waveform class for stress test electrocardiography ......................................................................... 8

5.2.3 Waveform class for full disclosure waveform ......................................................................................... 8

5.2.4 Waveform class for intermittent recorded waveform ..................................................................... 8

5.2.5 Waveform type for abstract waveform ......................................................................................................... 8

5.3 Lead name (Waveform attributes) ......................................................................................................................................... 9

5.4 Sampling attributes ..........................................................................................................................................................................10

5.5 Frame attributes .................................................................................................................................................................................10

5.6 Pointer .........................................................................................................................................................................................................10

5.7 Filter information ..............................................................................................................................................................................11

6 Load information ..............................................................................................................................................................................................11

6.1 General ........................................................................................................................................................................................................11

6.2 Loading related events ..................................................................................................................................................................11

6.3 Amount of load .....................................................................................................................................................................................13

7 Measurement information ......................................................................................................................................................................14

7.1 General ........................................................................................................................................................................................................14

7.2 Examination date/time .................................................................................................................................................................14

7.3 Rating of perceived exertion ....................................................................................................................................................15

7.4 R wave position ...................................................................................................................................................................................16

7.5 Interpretation and beat annotation ...................................................................................................................................17

7.6 ST segment recognition points...............................................................................................................................................17

7.7 ST segment measurement value ...........................................................................................................................................18

7.8 Other measurement value ..........................................................................................................................................................18

Annex A (informative) Encoding of ST segment recognition point and measurement value .................19

Annex B (informative) Encoding measurement value and interpretation ................................................................21

Annex C (informative) Example of waveform coding........................................................................................................................23

Bibliography .............................................................................................................................................................................................................................30

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ISO/TS 22077-4:2019(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 documents 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).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

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 Technical Committee ISO/TC 215, Health informatics.

A list of all parts in the ISO 22077 series can be found on the ISO website.

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.
iv © ISO 2019 – All rights reserved
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ISO/TS 22077-4:2019(E)
Introduction
0.1 General

Stress test electrocardiography is an examination that is frequently used. It is used to check the changes

in biological phenomena such as electrocardiogram or blood pressure that occur during cardiac stress.

Cardiac stress can be seen via exercise or by intravenous pharmacological stimulation. The purpose of

this examination is to find cardiac abnormalities, such as myocardial ischemia disease or arrhythmia

during exertion, and to check the athletic capability of the cardiopulmonary function.

This document defines the detailed rules of stress test electrocardiogram waveform format that is

encoded according to the Medical waveform Format Encoding Rules (MFER). In addition to basic rules

defined in ISO 22077-1, there are rules for ECG waveforms electrocardiography (12lead ECG, etc.) and

long-term electrocardiography (Holter ECG) that are contained in other MFER technical specifications,

i.e. ISO/TS 22077-2 and ISO/TS 22077-3. Please refer to those specifications for additional information.

0.2 Information package added to the electrocardiogram

The stress test checks the changes in the electrocardiogram during exercise against the resting

electrocardiogram. To correctly interpret the changes, we also need to capture other waveforms such

as the blood pressure, respiration gas, SpO and the load information. These should be put into a single

package to be delivered to a third party such as a healthcare provider.

The purpose of this document is to describe waveforms of different nature in the package and how they

can be synchronized in order to be interpreted simultaneously by the recipient of the package.

0.3 About electrocardiography waveform encoding in MFER

It is recommended to store the original waveforms as much as possible, i.e. waveforms are not

irreversible compressed or filtered. This is to avoid losing the information contained in the original

waveform when reusing the waveform in research, etc. It is desirable to perform the processing

(e.g., Synthesized lead or filtering) needed for encoded waveforms. The configuration and condition

of an electrocardiogram recording may be encoded with waveform data to assure reproduction of

electrocardiographic representation when using a system such as electronic medical records. However,

it is entrusted to the system whether those can or cannot be reproduced using this information. There

are often large drift noises and EMGs on electrocardiograms during exercise stress tests. Some devices

perform special signal processing to remove these noises. And the system might not be able to perform

the same signal processing to reproduce the electrocardiogram that was recorded. In such a case, in

addition to the original waveform, storing the waveform after signal processing is also an option.

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TECHNICAL SPECIFICATION ISO/TS 22077-4:2019(E)
Health informatics — Medical waveform format —
Part 4:
Stress test electrocardiography
1 Scope

This document defines the application of Medical waveform Format Encoding Rules (MFER) to

describe stress test electrocardiography, which is one of the outputs of exercise, pharmacological and

cardiopulmonary stress test. MFER performed in physiological laboratories, healthcare clinics, etc.

This document covers not only the electrocardiogram waveform but also the description of related

stress information and biological signals, e.g. blood pressure, respiration gas, SpO , etc..

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/TS 22077-2, Health informatics — Medical waveform format — Part 2: Electrocardiography

ISO/TS 22077-3, Health informatics — Medical waveform format — Part 3: Long term electrocardiography

3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1.1
abstract waveform

single beat ECG waveform which is extracted from all ECG waveform during examination period,

including the waveform which did the signal processing such as averaging
3.1.2
intermittent recording

recording electrocardiogram for a given period of time at a preset interval of time

3.1.3
full disclosure waveform

electrocardiographic waveform covering the entire time from the resting period (3.1.4) to the recovery

period (3.1.7) during cardiac stress test
3.1.4
resting period

phase before loading of stress (by exercise or medication) to the patient’s heart

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ISO/TS 22077-4:2019(E)
3.1.5
warm-up period
practise stage just before the start loading
3.1.6
loading period

phase immediately after the start loading with stress (by exercise or medication) to the patient’s heart

3.1.7
recovery period
end of loading with stress (by exercise or medication) to the patient’s heart
3.1.8
exercise stress test

examination procedure loaded to the heart to enable diagnosis of cardiac disease by exercise

Note 1 to entry: Ergometer and treadmill are representative methods for exercise stress loading.

3.1.9
pharmacological stress test

medication administered as a stress to the heart to enable diagnosis of heart disease

3.1.10
cardiopulmonary stress test

exercise stress test (3.1.8) to evaluate exercise capacity and predict outcome in patients with heart

failure and other cardiac conditions
3.1.11
borg scale

index used to express the exercise strength and to indicate the rating of perceived exertion

Note 1 to entry: The borg scale is generally used in exercise stress test.
3.2 Symbols and abbreviated terms
ECG Electrocardiogram
MFER Medical waveform Format Encoding Rules
SCP-ECG Standard Communications Protocol for Computerized Electrocardiography
SpO Saturation of Peripheral Oxygen
oxygen consumption
carbon dioxide output
VCO
minute ventilation
4 Outline of stress test cardiography rules
4.1 Configuration of waveform data (see Figure 1)

Medical waveform data described in accordance with the MFER is an aggregate of waveform frame

data that consists of a header section (encoding detailed information about the waveform) and a

waveform data section (main data of waveform). The header and waveform data are encoded based

on the encoding rules which are composed of TLV (Tag - Data length - Value). One MFER waveform file

can include several waveforms. The definition of the MFER waveform file is sequentially interpreted

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ISO/TS 22077-4:2019(E)

from the beginning of the file. As most definitions, multiple use is possible. The definition is used until

another definition for the same tag is encountered. Then the new definition replaces the older definition.

When there are several waveforms in a MFER waveform file, each waveform may be located anywhere

in the file. However, in the specification of stress test electrocardiography, waveform should be located

as follows for usability and to avoid erroneous interpretation.

— The information about stress test should be described before description of waveform. And the

value of waveform class definition (MWF_WFM) for the information should be ECG_EXER (stress

test ECG).

— The same type waveforms should be described in a mass and that should be located chronological.

Key
a. stress test information 1 tag
b. waveform (type #1) 2 length
c. waveform (type #2) 3 value
d. explanation about stress test 4 tag: MWF_WFM(8)
e. explanation (waveform class) 5 length: 2
f. waveform #1 of type #1 6 value: ECG_EXCER(4)
g. waveform #2 of type #1 7 tag: MWF_WAV(30)
h. frame #1 of waveform #1
i. frame #2 of waveform #1
j. header
k. waveform data
l. explanation about frame
Figure 1 — Configuration of waveform data
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ISO/TS 22077-4:2019(E)
4.2 Time synchronization (see Figure 2)

In the data of stress test electrocardiography, several types of electrocardiogram and biomedical data,

such as blood pressure, are described together. In addition, it is necessary to grasp the state of the load

at the time the data was acquired.

The reference time of description starts counting from examination beginning. The provider shall

describe the acquisition time which is defined using the reference time for each data. The user can get

the synchronization between data by collating the acquisition time for each data.

The reference time of waveform such as electrocardiogram is described using the pointer tag (MWF_

PNT). The reference time of events such as load information (loading period, recovery period, stage

period, etc.) is described using "starting time" item of the event tag (MWF_EVT). The reference time of

measurements such as blood pressure and the amount of load such as treadmill speed are described

using the "time point" item of the value tag (MWF_VAL). The reference time is indicated as a data pointer

which depend on the sampling rate of the frame. The user may get the synchronization using pointer of

different sampling rate.

For example, if the sampling interval of load information event is 1 second (s) and the sampling interval

of ECG waveform is 2 ms, then the point of load information event becomes 60 and the point of ECG

waveform becomes 30 000 at the time of the start of the load.
Key
1 load information
tag: MWF_EVT
code:
starting time: 60 s
2 60 s
3 start of examination
4 start of load
Figure 2 — Time synchronization
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ISO/TS 22077-4:2019(E)
5 Waveform encoding
5.1 General

This set of rules is aimed at ensuring that the waveforms collected serially during stress test

electrocardiography are encoded together with the information of the stress test. The waveforms

involved in stress test electrocardiography include “full disclosure waveform” (waveform in all

segments during the test), “intermittent record waveform” (waveform records in some short segments

during the test) and “abstract waveform” (waveform for a single heart beat extracted periodically

during the test).
5.1.1 Full disclosure waveform (see Figure 3)

This form is used when encoding all waveforms of electrocardiogram, etc., covering the resting

period (pre-loading), the loading period and the recovery period (post-loading). This includes not only

encoding of waveforms of all leads used in the test but also encoding of only the waveform for selected

one or multiple leads. It is a simpler description of full disclosure waveform to encode the waveform of

the entire period of the examination within one frame.

Encoding of full disclosure waveform shall be done in accordance with ISO/TS 22077-3. The waveform

class of this waveform is ECG_LTERM (2).
Figure 3 — Full disclosure waveform
5.1.2 Intermittent record waveform (see Figure 4)

This form is used when encoding the waveforms of electrocardiogram, etc., using the interval records at

the resting, the loading and the recovery periods or one-shot records taken at random during the test.

Encoding of intermittent record waveform shall be done in accordance with ISO/TS 22077-2. The

waveform class of this waveform is ECG_STD12 (1), ECG_SURF (6) or ECG_DRV (12), etc.

The point of time when the record concerned was taken during the test is encoded with using the

pointer tag (MWF PNT).
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ISO/TS 22077-4:2019(E)
Key
1 60 s after examination starting
2 120 s after examination starting
3 sampling interval: 2 ms
4 start of examination
Figure 4 — Intermittent record waveform
5.1.3 Abstract waveform (see Figure 5)

This form is used when encoding a group of electrocardiograms for individual heart beats extracted

at the resting, the loading and the recovery periods to evaluate changes in the characteristics of

electrocardiogram waveforms during the test.

The abstract waveform includes not only the extracted waveform which is one beat during a certain

period but also the average waveform which averaged several beats during a certain period. In addition,

it includes a derived waveform which is made by a special signal processing. Encoding of an abstract

waveform is done in accordance with ISO/TS 22077-2. The waveform class of this waveform is ECG_

BAET (9).

The abstract waveforms at the same time are encoded as one frame, and there are frames of abstract

waveforms which are extracted each time. The pointer tag (MWF_PNT) of frame indicates the time of

an abstract waveform.
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ISO/TS 22077-4:2019(E)
Key
1 sampling interval: 2 ms
2 start of examination
3 start of load (resting)
4 3 min after load
5 end of load (post exercise)
Figure 5 — Abstract waveform
5.2 Waveform class
5.2.1 General

The waveform class indicates that this waveform data is as stress test ECG. Furthermore, the waveform

class indicates the kind of waveform that included in this data. The format is given in Table 1.

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ISO/TS 22077-4:2019(E)
Table 1 — Waveform class
MWF_WFM Data length Default Remarks Duplicated definitions
2 Non-specific waveform Override
08 08h
Str ≤ 32 Waveform description Override
5.2.2 Waveform class for stress test electrocardiography

A description of waveform class for stress test ECG shall be provided in the data. This description shall

precede the description of the waveform class of the waveforms included in this data.

The type for this waveform is designated in Table 2.
Table 2 — Stress test ECG waveform
Classification Type Value Waveform description Remarks
Exercise stress test ECG
Pharmacological stress test ECG
Electrocardiogram ECG_EXCER 4 Stress test ECG
Cardiopulmonary stress test
ECG
5.2.3 Waveform class for full disclosure waveform

The waveform class for full disclosure waveform is "Long term ECG". Long term ECG waveform should

be encoded in accordance with ISO/TS 22077-3.
The type for this waveform is designated in Table 3.
Table 3 — Full disclosure waveform
Classification Type Value Waveform description Remarks
Electrocardiogram ECG_LTERM 2 Long term ECG Full disclosure ECG
5.2.4 Waveform class for intermittent recorded waveform

The waveform class for intermittent record waveform is "Standard 12lead ECG", etc. This waveform

should be encoded in accordance with ISO/TS 22077-2.
The type for this waveform is designated in Table 4.
Table 4 — Intermittent record waveform
Classification Type Value Waveform description Remarks
Standard 12lead ECG including
ECG_STD12 1 Standard 12lead ECG general ECG in short term
recording.
Electrocardiogram Frank’s lead, chest bipolar lead,
ECG_SURF 6 Body surface ECG
Nehb lead, etc.
Derived ECG from Frank vector
ECG_DRV 12 Derived lead
leads, EASI lead, etc.
5.2.5 Waveform type for abstract waveform

The waveform class for abstract waveform is "QRS beat". This waveform should be encoded in

accordance with ISO/TS 22077-2.
The type for this waveform is designated in Table 5.
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ISO/TS 22077-4:2019(E)
Table 5 — Abstract waveform
Classification Type Value Waveform description Remarks
One heart beat waveform which
the abstraction is made periodi-
Electrocardiogram ECG_BEAT 9 QRS beat
cally during the examination.
Average, median, dominant, etc.
5.3 Lead name (Waveform attributes)

Lead name means the waveform code that is one of waveform attributes. The format is as Table 6.

Table 6 — Definition of waveform attributes
Data Duplicated
MWF_LDN Default Remarks
length definitions
Data length = 2,
Waveform code 2 Override
if waveform information is
09 09h undefined
encoded
Waveform
Str ≤ 32 — Override
information

This is the waveform code used in stress test ECG. As the lead code is encoded by the number 0-127,

extra attention would be required in the case of conforming with other rules such as SCP-ECG.

Table 7 — Lead name 1
Code Lead Code Lead Code Lead Code Lead
0 Config 32 CB4 64 aVF 97 —
1 I 33 CB5 65 (-aVR) 98 —
2 II 34 CB6 66 V8 98 —
3 V1 35 — 67 V9 99 —
4 V2 36 — 68 V8R 100 —
5 V3 37 — 69 V9R 101 —
6 V4 38 — 70 Nehb-D 102 —
7 V5 39 — 71 Nehb-A 103 —
8 V6 40 — 72 Nehb-I 104 —
9 V7 41 — 73 — 105 —
10 (V2R) 42 — 74 — 106 —
11 V3R 43 — 75 — 107 —
12 V4R 44 — 76 — 108 —
13 V5R 45 — 77 — 109 —
14 V6R 46 — 78 — 110 —
15 V7R 47 — 79 — 111 —
16 X 48 — 80 — 112 —
17 Y 49 — 81 — 113 —
18 Z 50 — 82 — 114 —
19 CC5 51 — 83 — 115 —

Although V2R (10) is defined in other rules such as SCP-ECG, the definition shall not be used in MFER. V2R shall be

used as V1.

-aVR lead shall not be encoded according to MFER. The users (viewer) shall make a calculation to derive –aVR when

required.
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ISO/TS 22077-4:2019(E)
Table 7 (continued)
Code Lead Code Lead Code Lead Code Lead
20 CM5 52 — 84 — 116 —
21 — 53 — 85 — 117 —
22 — 54 — 86 — 118 —
23 — 55 — 87 — 119 —
24 — 56 — 88 — 120 —
25 — 57 — 89 — 121 —
26 — 58 — 90 — 122 —
27 — 59 — 91 MCL 123 —
28 — 60 — 92 — 124 —
29 — 61 III 93 — 125 —
30 — 62 aVR 94 — 126 —
31 NASA 63 aVL 95 — 127 —

Although V2R (10) is defined in other rules such as SCP-ECG, the definition shall not be used in MFER. V2R shall be

used as V1.

-aVR lead shall not be encoded according to MFER. The users (viewer) shall make a calculation to derive –aVR when

required.
Table 8 — Lead name 2
Code Lead Remarks
175 SpO
In case status including pacing and lead off. Status should be
4160 Status
encoded in accordance with ISO/TS 22077-3.
4166 ECG1
4167 ECG2
These shall be used in case le
...

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