March 1999
This section provides the equivalent of a manual of operations for the collection and processing of data for this component of the MONICA Project.
The MONICA core study is concerned with coronary and stroke events (and not with persons) and with two characteristics of the events, apart from their diagnostic category, which are whether they are (a) first or recurrent, and (b) fatal or non- fatal. Each episode must have a defined duration. In the MONICA core study a period of 28 days is used to establish the case-fatality and to distinguish two events from each other.
The Protocol (WHO/MNC/82.1 Rev. 1) was the first document describing the principles of event registration. Modifications and clarifications have been agreed by the Council of Principal Investigators and these were included in MONICA MEMOs 30, 40, 41, 49 and 57. This Manual contains the latest information which should always be used.
It is important that event registration procedures are similar throughout the entire study period in each MCC or in each Reporting Unit. There are some differences causing systematic bias between MCCs which cannot be avoided and, therefore, the data from different centres will not be fully comparable. If this systematic bias within each MCC is kept unchanged, it will be possible to compare trends in incidence and case-fatality both between and within centres because the changes over time will then be independent of the systematic bias. The most important source of systematic bias in estimating incidence is related to the coverage of event registration. The aim of event registration is to get as near to 100% coverage as possible, i.e. to ascertain the maximum number of coronary events and stroke events in the study population.
Certain factors may influence the detection of events and calculation of the event rates such as instability of the population, seasonal migration and permanent migration in and out of the study area. Populations for event registration must be the same as the defined Reporting Units in each MCC. The denominator must be the same for event registration and for the population surveys. The population size estimates for each Reporting Unit must be reported annually to the MDC from the MCC using the Population Demographics Reporting Form.
For an event to qualify for inclusion in the MONICA study:
The suspect events are collected from death certificates, from hospital medical records and from community health services. These suspect events are examined for eligibility into the Coronary and Stroke register. Event finding may be;
Some sources of event finding may provide information a long time only after the actual event occurred. Typical examples of such situations are: National Hospital Discharge Registers, Registers for Social Security Purposes and Death Certificate Registers. One to two years delay may occur. There is no preset time limit for including such events in the coronary or stroke register if the criteria are otherwise met (e.g. they must have been clinically recognised within 28 days of onset even if there was a delay in registering them). However, the Data Centre may have to impose such a time limit at the end of the study, in order to bring it to an end. These late events can be identified in the database by using the date of event (DONSET) and the date of registration (DREG) and appropriate methods of data analysis can be applied. Another problem is that of cases identified reasonably early for whom case records remain unavailable. Again local policy and discussion with the Data Centre will determine the optimum policy for balancing complete registration with completing a year's registrations reasonably quickly.
In each MONICA Reporting Unit an information gathering system will need to be instituted (1) to gain information on likely events, and (2) to obtain all available diagnostic and other information.
The sources used must depend on the structure of the local medical and medico- legal services.
The following sources may be used to identify cases:
The first two sources are obligatory but the others will depend on the local situation.
Once sources and ICD codes have been determined in the MCC or in the Reporting Unit it is important that methods are not changed over time without measuring the consequences, as a change of sources may cause a spurious change in event rates.
All death certificates of the residents of the MONICA Reporting Unit areas should be reviewed at least quarterly or semiannually.
Periodically during the 10-year period a random or stratified sample of hospital cases should be taken to search for changes in the pattern of cases. Where multiple field discharge data are available a different set of rules may be applied for main and subsidiary diagnoses.
While each MCC should attempt to find all the death certificate codes both as immediate, main and antecedent or underlying causes of death that lead to cases of coronary heart attack and stroke satisfying the MONICA criteria, at least the following causes of death should be considered during pilot studies:
| Cause of death | ICD code | |
|---|---|---|
| Diabetes | 250 | |
| Hyperlipidaemia | 272 | |
| Obesity | 278 | |
| Cardiovascular | ||
| Hypertensive | 401-405 | |
| Ischaemic | 410-414 | |
| Other | 420-429 | |
| Stroke | 430-439 | |
| Arteries,etc. | 440-447 | |
| Symptoms, etc. | 797-799 | |
It is therefore possible to exclude those deaths that are clearly due to trauma (e.g. contain a sequence of events including accident, homicide or suicide), chronic obstructive pulmonary disease, cancer, cirrhosis of the liver, or rheumatic heart disease without mention of atherosclerotic heart or vascular disease. However, if an atherosclerotic condition is mentioned in the sequence of events or if the cause of death is attributed to one of the conditions listed above, the cause of death should be validated. Where deaths are notified through medico-legal sources all non-violent sudden deaths, hospital "dead on arrival" and deaths from cardiovascular disease within 24 hours of onset should be monitored.
Validation is based on any available medical and medico-legal records and, if necessary (local option) interview of the decedent's next-of-kin or another informant. Medical records for the period within a minimum of 28 days of death should also be examined for information that may elucidate the circumstances leading to the death. The interview should establish the circumstances surrounding the decedent's death.
Deaths should be validated by applying the MONICA diagnostic criteria for coronary events (see 2.2). These are based on the symptom history, ECGs, cardiac enzymes, necropsy and death certificate data. In positive cases diagnostic findings should be recorded on the locally used MONICA Coronary Event Registration Forms. In those centres undertaking stroke registration diagnostic criteria should be applied for stroke using similar sources of data. In positive cases diagnostic findings should be recorded on the locally used MONICA Stroke Event Registration Forms.
The list of death certificate codes produced above was for use during the development of the MONICA Registration procedures in each MONICA Collaborating Centre. Where, after pilot studies, a more limited list is being monitored, because certain codes were found to be unproductive, then the full list should be used periodically to see that the situation has not changed. All deaths with the underlying cause coded to 410-414 must be registered even if they are found not to be a coronary case on examination. Stroke registers should register all cases where the ICD code implies acute stroke (ICD 430-4 and 436) even if they are found not to be strokes alone.
It is the experience in some countries that practically all myocardial infarctions are identified as such but not all cases identified as myocardial infarction meet the criteria for MONICA coronary events. To ensure that this is the case in all MCCs using discharge diagnoses ("cold pursuit") as the source of case finding it is suggested that each centre starts with a range of discharge codes that is broader than 410 and 411 (e.g. codes for chronic ischaemic heart disease and non- ischaemic heart disease, atherosclerosis, pulmonary embolism and other syndromes associated with chest pain or undiagnosed chest pain) and document that an insignificant proportion of cases with a definite coronary event are included in these discharge codes.
For those centres employing "hot pursuit" on the other hand it is necessary to monitor all acute medical admission wards as well as hospital laboratory data on cardiac enzymes and ECGs to be sure that all cases have been detected.
It is suggested that in the early phases of data collection each MCC collect data on cases drawn from a broad range of discharge codes which might include stroke assigned to another category. Examples of these belong to the categories (ICD-9) 430-438 but might also include hemiplegia (342), "certain symptoms referable to the nervous system and special senses" (781). Once it has been established that an insignificant proportion of cases discharged without stroke diagnoses are in fact not stroke, case validation can proceed on a narrower scale (e.g. 430-436 or 438). Documentation of the adequacy of such a narrower scale should be repeated every two to five years to make sure that there has been no change in hospital labelling practice over time.
Out-of-hospital treatment of acute myocardial infarction is not common in most cities. Such cases may be detected from clinical pathology laboratory records for cardiac enzymes and electrocardiographic laboratory records if these are used in the study centre's area. In communities where acute myocardial infarction patients may be treated out of hospital attempts should be made to define the proportion of such events by questioning physicians in the community. A protocol should be developed as part of the Manual of Operations of the MCC to identify and collect data on coronary events treated out of hospital.
In communities where patients in the 25-64 age range with stroke are not always treated in hospital, routine searches outside will be cost effective, but even where hospital treatment is said to be the norm, this should be confirmed by questioning physicians in the community in the pilot phase. However, in those countries where stroke is treated at home, contact must be made with physicians and a protocol established to identify and collect data on stroke cases. This procedure could take several forms and might include reviewing charts on a semi- annual basis, providing each office with a log book and a poster reminding them to log all cases of suspected new stroke, or asking the office nurse or assistant to notify the project when a new stroke is identified.
Each coronary and stroke event is defined as lasting for 28 days (unless interrupted by death) so that any recurrence or exacerbation of the condition within that period is counted as part of the original episode whereas beyond that time it counts as a new (recurrent) episode. A special problem arises in those centres who are registering both coronary and stroke events in dealing with cases who satisfy criteria for both coronary and stroke events within one 28 day period, or in which the clinical diagnosis is of one condition, but the diagnostic evidence suggests that the other is more probable. Such events should be discussed by both registration teams.
Each MCC should lay down its own rules and should adhere to them so that there is no systematic bias over time. The number of events involved is small and should not have a big effect on registration numbers whatever method of handling the problem is used. The following rules are recommended; these should be acceptable to both those centres that are registering coronary events and strokes and those that are registering coronary events alone.
Cases satisfying criteria for definite myocardial infarction should be registered as such whether or not an apparent stroke occurs within 28 days before or afterwards.
Definite strokes should also be registered but if they occur in association with a definite myocardial infarction (within 28 days before or after), for stroke the diagnostic category 5 can be used, rather than 1. The event would be registered in both the coronary and stroke registers but could be removed from the latter by excluding category 5 if this was wanted.
Patients who die from a combined definite myocardial infarction and definite stroke within 28 days of onset of acute symptoms should be counted as fatal cases in both registers but again could be removed from the stroke register for certain analyses if necessary as they would be coded as category 5.
In cases where definite evidence for one of these two diseases is mixed with possible or inadequate data evidence for the other, the definite diagnosis should take precedence and the possible diagnosis should not lead to registration unless the secondary diagnosis appears as the underlying cause of death on the death certificate, or as a major clinical diagnosis when the case is notified. In these cases the patient would appear in the register of the definite disease as a Definite case and in the register of the unproven disease as a Not case, or false positive. In these cases it would be clear from the clinical diagnoses or the death certificate diagnoses on the record form what had happened to make it a false positive.
Cases with inadequate data which could be either coronary or stroke events should not be assigned to both registers as inadequate data but should be allocated the most probable diagnosis, regardless of what the death certificate diagnosis states. A case diagnosed on the death certificate as stroke which on investigation is more like a coronary death should therefore be coded as an inadequate data case in the coronary event register and as DIACAT 4 in the stroke register.
In order to define the diagnostic category of a suspect event information about the following four data items must be collected:
The rest of the data to be collected by Core Data Transfer Format -Coronary Events are essential for statistical analysis and quality assurance of the data.
Every coronary event must have its apparent onset within the study period and more than 28 days from any preceding recorded coronary event in the individual. Secondly, the event must be detected and diagnosed within 28 days of onset. The actual way of calculating the 28-day survival period is described in the instructions for CORE DATA TRANSFER FORMATS - CORONARY EVENTS. The principles are that the day of onset is day zero and that the difference in calendar days is calculated by subtracting date of onset from date of death.
Any recurrent event in one individual occurring after midnight between days 27 and 28 must be considered as a separate event.
The starting point for calculating the 28-day survival period is the onset of the first manifestation of a suspect coronary event (symptoms, ECG, enzymes). If recurrences happen during the next 28 days they belong to the same event. In coronary events the most severe findings for symptoms, enzymes and ECG detected during the 28-day survival period should be reported - for instance if a patient has first atypical symptoms or enzymes other than abnormal but later on he/she has a recurrent event with typical symptoms or abnormal enzymes, one should code symptoms typical and enzymes abnormal. This procedure for the diagnostic findings of recurrent events should not influence the date of onset of the event.
Because the 28-day survival period is the only basis for the assessment of case- fatality it is essential that the date of onset of an event is recorded in the same way during the entire study period. Every MCC should pay special attention to consistency during the study period.
Maximum effort should be put on the accurate ascertainment of the survival status at 28 days in every event.
It is important to obtain the best available information about the previous history of myocardial infarction in each event in order to separate first events from recurrent events. The data item "Previous history of myocardial infarction" is the variable which allows this separation. The procedures for collection of these data should be kept constant throughout the entire study.
Because each event lasts only 28 days the diagnostic criteria used must be from investigations or symptoms that refer to what happened within that 28 day survival period even though the results (such as necropsy or enzyme tests) may be reported later. The definition of the 28-day survival period has been given earlier.
The most severe findings during the 28-day survival period should always be recorded. This means that in case of recurrent events during the 28-day period symptoms should be coded "typical" if in any of the recurrent attacks the criteria for typical symptoms were met. Accordingly enzymes should be coded "Abnormal" if in any of the recurrent attacks the criteria for abnormal enzymes were met. This also means that symptoms, enzymes and ECG findings may refer to different attacks occurring within the 28-day period.
There are the following categories:
(1) definite acute myocardial infarction
(2) possible acute myocardial infarction or coronary death
(3) ischaemic cardiac arrest with successful resuscitation not fulfilling criteria for definite or possible myocardial infarction
(4) no acute myocardial infarction or coronary death
(9) fatal cases with insufficient data, subsequently called "unclassifiable deaths" in collaborative MONICA publications
Allocation of a diagnostic category must follow strictly the definitions provided. The criteria used for the diagnosis of "definite" and "possible" acute myocardial infarction are not necessarily those that would be used by a clinician, but rigid definitions are essential for event analysis.
- with symptoms typical or atypical or inadequately described, or
- without typical or atypical or inadequately described symptoms but with evidence of chronic coronary occlusion or stenosis or old myocardial scarring at necropsy; or
- with a good history of chronic ischaemic heart disease such as definite or possible myocardial infarction, or coronary insufficiency or angina pectoris in the absence of significant valvular disease or cardiomyopathy.
NOTE: A strict watch should be kept over competing causes of death. Local rules should be standardized and record kept of difficult decisions.
Spontaneous cardiac arrest not provoked by medical intervention, electrocution, drowning or other gross physical insults, from presumed primary ventricular fibrillation secondary to ischaemic heart disease, in the absence of significant valvular disease or cardiomyopathy.
Note: this category was little used and was excluded from the main MONICA collaborative analyses.
NOTE: A strict watch should be kept over competing causes of death. Local rules should be standardized and a record kept of difficult decisions.
Cases with no autopsy, no history of typical or atypical or inadequately described symptoms, no previous history of chronic ischaemic heart disease and no other diagnosis. Living patients should not be allocated to this category. It is hoped that most centres will not need this category.
Note: unfortunately this was a vain hope, as this category accounted for a large proportion of deaths in many centres. It was renamed "unclassifiable deaths" in the main collaborative papers on coronary events.
(Note added in 1999.)
There are four categories of nonfatal events and three categories of fatal events, each of which is potentially divisible into a number of sub-categories. It was decided early in the development of the MONICA protocol that nonfatal definite events (NF1) should be the main endpoint for nonfatal events for the study as a whole. This was because nonfatal possibles (NF2) were less well defined, were more likely to be missed, were more dependent on the source of notification and registration, such as hot pursuit and cold pursuit, and the ratio of these to definites therefore varied greatly between centres. Conversely, although fatal events with inadequate data (F9), later called unclassifiable deaths, had similar problems, they accounted for so many presumed coronary deaths in many centres that they had to be included. Although the prime definition was Definition 1, discussion on these issues led to the definition of other combinations of MONICA coronary events for the first cross-sectional publication on coronary events.[1]
A subsequent cross-sectional analysis of nonfatal possible events, involving most, but not all, MONICA centres produced MONICA coronary events Definition 4, which was equivalent to Definition 3, but including only those subcategories of nonfatal possibles in which there was some diagnostic evidence for coronary heart disease.[2]
Note that the categories NF3 (ischaemic cardiac arrest with survival to 28 days) and NF4 and F4 (no myocardial infarction or coronary event) are not included in any of the above definitions. Sudden death from coronary heart disease without evidence of acute myocardial infarction was relatively common (F2 and potentially F9) but the number of registrations of those successfully resuscitated from cardiac arrest in this situation (F3) was so small as to be insignificant. This was because they were rare, but the register process may not have found them all.
The diagnostic algorithm for coronary events was first circulated from Dundee as MONICA MEMO 40 (dated 25.2.85) and this Dundee algorithm was adopted into MONICA MEMO 49 and 57 and officially adopted by the Principal Investigators Meeting in August 1985. In MONICA MEMO 40, it was stated that a completely automated diagnosis from the diagnostic criteria was not possible using the information on the Core Data Transfer Form for Coronary Events. The reason for this is that whether or not a case involves resuscitation from cardiac arrest and has evidence of coronary disease (such as coronary angiography) may determine whether a non-fatal case is categorized as category 3 (Ischaemic cardiac arrest) or category 4 (No myocardial infarction). This information is not core data. In fatal cases the presence or absence of a competing diagnosis may determine how a case is coded so that category 4 (No myocardial infarction) is competing with category 2 (Possible coronary death), and with category 9 (Inadequate data). Priority of diagnoses could be done by giving an order of priority to the ICD codes on the death certificate, so that, for example, a diagnosis of carcinoma precludes a possible coronary death. However, the ICD code diagnosis may be considered inadequate as a criterion by itself without any indication of severity (for example, centres who are able to obtain case notes, can tell whether a carcinoma coded on the death certificate had been radically treated, or whether it was regarded as metastasizing, advanced and incurable at the time of death). MONICA MEMO 74 took the diagnostic algorithm a stage further. MEMO 40 contained 24 diagnostic permutations for non-fatal cases and a description of the process for fatal cases. The present algorithm has been used to examine all the possibly permutations of the Core Data Transfer items that determine diagnosis. Most of them will never occur but they enable MCCs to compare the performance of their own computer programs, and coders without access to a computer program can use the table printed here to check their coding. This algorithm is being used in Dundee to check test case histories and in Helsinki by the Data Centre to check the submitted event data.
DUNDEE DIAGNOSTIC ALGORITHM (Version 3, 9.6.86)
For purposes of analysis many of the different values of the diagnostic criteria are equivalent in determining the diagnostic category. For the following arguments the = sign will mean "is equivalent to" for deriving the diagnostic category. (It does not mean that the codes are interchangeable for other purposes because each code is thought to convey distinct information). "Effective codes" means codes that are effectively different. For the diagnostic algorithm convert the equivalent codes into the one with the value specified as the effective code (but note composite code for history of ischaemic heart disease and previous myocardial infarction). The permutation list considers these simplified values only, so you will have to convert other values to these simplified values when making a comparison.
| ITEM | NUMBER | CODE SIMPLIFICATION | |
|---|---|---|---|
| SURVIV | 11: | 9=1 Effective codes therefore are 1,2 (2 categories) | |
| SYMPT | 12: | 2=5, 3=4=9 Effective codes therefore are 1, 2, 3 (3 categories) | |
| ECG | 13: | 3=5=9 Effective codes therefore are 1, 2, 3, 4 (4 categories) | |
| ENZ | 14: | 2=3=4=5=9 Effective codes therefore are 1, 2 (2 categories) | |
| NECSUM | 15: | 9=8 Effective codes therefore are 1, 2, 4, 8 (4 categories) | |
| PREMI | 22: | 1=2=3=4=5, 6=7, effective codes are 1,6,9. | |
| HISIHD | 30: | 1,2,9. |
Examine diagnostic criteria in the following sequence: (Comments in brackets)
If ECG 13 = 1
or NECSUM 15 = 1,
or SYMPT = 1 or 2 and ECG = 2 and ENZ = 1
or SYMPT = 1 and ECG = 3 and ENZ = 1
the DIACAT 16 = 1, Definite, whether patient is alive or dead.(SURVIV 11= 1 or 2)
(Comment: Note that definite criteria in life can take precedence over a negative necropsy).
If SURVIV 11 = 1 and SYMPT = 1 and NECSUM = 2. DIACAT = 2
(Comment: this is illogical but the diagnostic category is the same whether the case was fatal or non-fatal, so that despite the conflict of criteria a diagnostic category is possible)
If SURVIV 11 = 1 (and/or was 9) and NECSUM = 2 or 4. Allocate new DIACAT = 8 and print "Illogical uncodable"
(Comment: this combination is illogical and the diagnostic category would be affected by which of the conflicting criteria is given precedence so no category is possible. Code 8 does not officially exist and has been used just for this algorithm.)
If SURVIV 11 = 1 and SYMPT = 1, DIACAT = 2
(Comment: it is not possible to decide between 4 and 3 using core data items)
If NECSUM 15 = 4, DIACAT = 4
If NECSUM 15 = 2, DIACAT = 2
If SYMPT 12 = 1, DIACAT = 2
If SYMPT 12 = 2, DIACAT = 2
(Comment: Competing diagnoses prevent the use of symptom codes 1 and 2)
If PREHIS = 1, DIACAT = 2 or 4
If PREHIS = 2 or 9 DIACAT = 4 or 9.
(Comment: presence of competing diagnoses decide whether the category is 4 or not)
The presentations of all these items are considered in the table of Annex1.
The ECG classification will be based on the reading of records taken in the 28 days following the acute attack and, if available, records taken immediately before (i.e. within the previous 28 days). Up to four records should be selected for coding of change and the choice should be standardized. The following is a recommendation:
Local discretion to be used if:
It is recommended that photostats of ECGs should be obtained wherever possible for potential duplicate coding and quality control.
ECGs should be coded individually using a combination of the MONICA Protocol criteria and the Minnesota Code Manual of Electrocardiographic Findings, [3] plus a transparent ruler and a coding lens. Each record should be coded individually for Minnesota 1, 4, 5, and 9.2 codes within lead groups (anterolateral I, aVL, V6; posterior (inferior) II, III and aVF; and anterior V1,V2,V3,V4,V5) and for suppression codes (listed later). The standard procedure will be that a written record is kept of individual codes as a method of quality control for duplicate coding and so that the MONICA ECG classification can be derived by inspection of the sequence of codes. A computer algorithm is feasible using changes within lead groups to generate a MONICA ECG classification (see Paragraph 2.5). The MONICA criteria are therefore based on the sequence of individual codes as described here; and without applying the criteria for significant serial change described in the Minnesota Code Manual. The ECG records as a whole should be coded to the most severe class applicable. If in doubt code to the less severe alternative.
Note that the ECG codes that follow are the two-digit codes used in the computer algorithm. Only the first digit is used in the coronary event transfer format.
(A) The development in serial records of a diagnostic Q wave (as characterized below)
-AND/OR-
(B) The evolution of an injury current which lasts more then one day. (as characterized below)
(note: criterion B is included because diagnostic Q waves are already present in the first ECG recording in many cases. The presence of Q waves is not necessary to satisfy this criterion)
The interpretation of a minimum of two or sometimes three ECG records is therefore necessary for the establishment of these categories. (Not more than four to be coded. Four should be coded ideally if they are available.)
Progression of Q codes from no Q to a diagnostic Q is sufficient but change from no Q to an equivocal Q or from equivocal to diagnostic Q must be accompanied by deterioration in the ST segment or the T wave. A change in a Q code or in a 4, 5 or 9-2 code must occur within the same lead group but the Q can be in a different lead group to that in which the 4, 5 or 9-2 code is being followed. Note that Minnesota code 1-2-6 is equivalent to No Q code.
| 1.1 | No Q or QS code in the first ECG record followed by a record with a diagnostic Q or QS code (Minn. code 1-1-1 through 1-2-5 plus 1-2-7) |
-OR-
| 1.2 | An equivocal Q or QS code (Minn. code 1-2-8 or any 1-3 code) and no major ST segment depression (No Minn. code 4-1 or 4-2) in the first ECG record followed by a record with a diagnostic Q code PLUS a major ST segment depression (Minn. code 4-1 or 4-2) |
-OR-
| 1.3 | An equivocal Q finding and no ST segment elevation (No Minn. code 9-2) in the first ECG record followed by a record with a diagnostic Q code PLUS an ST segment elevation (Minn. code 9-2) |
-OR-
| 1.4 | An equivocal Q finding and no major T wave inversion (No Minn. code 5-1 or 5- 2) in the first ECG record followed by a record with a diagnostic Q code PLUS a major T inversion (Minn. code 5-1 or 5-2) |
-OR-
| 1.5 | No Q code and neither 4-1 nor 4-2 in the first ECG followed by a record with an equivocal Q code PLUS a 4-1 or 4-2 |
-OR-
| 1.6 | No Q code and no 9-2 in the first ECG followed by a record with an equivocal Q code PLUS a 9-2 |
-OR-
| 1.7 | No Q code and neither 5-1 nor 5-2 in the first ECG followed by a record with an equivocal Q code PLUS a 5-1 or 5-2 |
-OR-
| 1.8 | An ST segment Elevation (Minn. code 9-2) lasting more than one day (i.e. present on consecutive records of different dates) |
AND
T wave progression on three or more records from 5-0 to 5-2 or from 5-3 to 5- 1, with a more abnormal code present on consecutive records of different dates. (See VERBAL EXPLANATION OF ALGORITHM, definition of DEFINITE 1.8, paragraph 2.5).
Note: The ST segment elevation does not have to be present in the same lead groups as the T progression, nor does it have to be exactly simultaneous. Q waves will often be present in the same graphs but they are not necessary to the use of this criterion for Definite ECG.
Evolution of repolarisation changes
| 2.1 | No major ST segment depression in one ECG record (no 4-1 or 4-2) and another record with a major ST segment depression (Minn. code 4-1) |
| 2.2 | No ST segment elevation in one ECG record (no 9-2) and another record with an ST segment elevation (Minn. code 9-2) |
| 2.3 | No major T wave inversion in one ECG record (no 5-1 or 5-2) and another record with a major T wave inversion (Minn. code 5-1 or 5-2) |
Note: Unlike the criteria in the previous classes, the evolution in this class can go in either direction, that is the codes can get better or worse.
Note also that the criteria are not identical to those for repolarisation criteria accompanying the Q classes 1.2 to 1.7 in that the 4 code is more severe; the development or disappearance of 4-2 does not qualify; it has to be a 4-1.
Records not satisfying the above criteria which nonetheless show:
| 3.1 | Minnesota codes 1-1-1 to 1-3-6 excluding 1-2-6 for Q and QS codes. |
-AND/OR-
| 3.2 | Minnesota codes 4-1 through 4-3 for ST junction (J) and segment depression. |
-AND/OR-
| 3.3 | Minnesota codes 5-1 through 5-3 for T wave items. |
-AND/OR-
| 3.4 | Minnesota code 9-2 for ST segment elevation. |
All other ECG findings, including normal ECG but note rules for uncodable ECG below.
This class should be used where all the available ECG records taken in the attack are uncodable for technical reasons or because of the presence of suppression codes. Records in which suppression codes permit certain Q codes to appear could be used to diagnose the development of a diagnostic Q code from no Q code (MONICA ECG code 1.1) or to allocate the code of ischaemic ECG (MONICA ECG code 3.1); supporting evidence from 4, 5, and 9-2 codes are needed for all other MONICA ECG classes. Therefore, unless codable Q waves are present leading to the diagnostic or ischaemic category, and unless at least one ECG is available that can be coded for 1, 4, 5 and 9-2 items then the presence of suppression codes or technically unsatisfactory records should lead to the allocation of the classification "uncodable". The implications of this rule are that ventricular conduction abnormalities and arrhythmias occurring in the course of an event are not used as collateral evidence of ischaemia.
The following Minnesota codes lead to suppression of all or most of these items, and a set of ECG records in which such findings are present in all records should be considered uncodable (unless codable Q waves are present, for example in an ECG showing a 7-4)
| 6-1 | Third degree A-V block, suppresses all 1,4,5 and 9-2 |
| 6-4-1 | Persistent Wolff-Parkinson White Pattern, suppresses all other codes. |
| 6-8 | Artificial pacemaker, suppresses all other codes. |
| 7-1-1 | Complete left bundle branch block, suppresses 1-2-3,1-2-7,1-2-8, 1-3-2, 1-3-6 and all 4, 5 and 9-2 codes but the presence of a codable Q downgrades it to 7-4. |
| 7-2-1 | Complete right bundle branch block, suppresses 1-2-8, and all 4, 5 and 9-2 codes. |
| 7-4 | Intraventricular block suppresses all 4, 5, and 9-2 codes. |
| 8-2-1 | Ventricular fibrillation and asystole, suppress all other codes |
| 8-2-2 | Idioventricular rhythm, suppresses all other codes. |
| 8-4-1 | Supraventricular tachycardia above 140/minute, suppresses all other codes. |
No ECG available or recorded. (Coded as 9, no data)
Coding of the electrocardiogram will involve, in the majority of centres, the recording of the Minnesota codes of consecutive (up to 4) electrocardiograms, followed by the allocation of a MONICA category based on the MONICA protocol. The derivation of the MONICA category should be automatic given a particular sequence of Minnesota codes for the electrocardiograms and a computer algorithm was written in Dundee in BASIC language and has been made available to other centres on request. (See MONICA Memos 41 and 67; MNM 41 contains examples and MNM 67 contains a listing). The algorithm was officially adopted by the Principal Investigators at the 1985 meeting.
In deriving the algorithm some ambiguities were discovered in the verbal description of the ECG codes. In particular for MONICA code 1.8, it was decided to allow the sequences: 5.0, 5.2,5.2; 5.0,5.3,5.2 and 5.0,5.2,5.3 as being covered by the wording "progression from 5.0 to 5.2 with a more abnormal code present on consecutive dates" with 5.0, 5.3,5.3 excluded.
Many of the sequences have explanations. The code numbers are those used in the MONICA Electrocardiographic criteria (Paragraph 2.4).
VERBAL EXPLANATION OF ALGORITHM
The algorithm as written for the computer has five stages:
The algorithm is based on the following MONICA code definitions:
DEFINITE CODES 1.1 TO 1.7
| First record with .......... | Followed by a record with..... | |||
|---|---|---|---|---|
| DEFINITE 1.1 | - NO Q code | DIAGNOSTIC Q | ||
| DEFINITE 1.2 | - EQUIVOCAL Q | + NO 4-1 or 4-2 | DIAGNOSTIC Q | + 4-1 or 4-2 |
| DEFINITE 1.3 | - EQUIVOCAL Q | + NO 9-2 | DIAGNOSTIC Q | + 9-2 |
| DEFINITE 1.4 | - EQUIVOCAL Q | + NO 5-1 or 5-2 | DIAGNOSTIC Q | + 5-1 or 5-2 |
| DEFINITE 1.5 | - NO Q | + NO 4-1 or 4-2 | EQUIVOCAL Q | 4-1 or 4-2 |
| DEFINITE 1.6 | - NO Q | + NO 9-2 | EQUIVOCAL Q | + 9.2 |
| DEFINITE 1.7 | - NO Q | + NO 5-1 or 5-2 | EQUIVOCAL Q | + 5-1 or 5-2 |
DEFINITE 1.8 -
9-2 in consecutive records on different dates plus T progression in 3 records 5-0 to 5-2 or 5-3 to 5-1:
Examples:
5-0, 5-2, 5-2;
5-0, 5-3, 5-2;
5-0, 5-2, 5-3,
or substitute 5-1 for 2nd or third:
5-3, 5-2, 5-1;
5-3, 5-1, 5-2;
5-3, 5-1, 5-1.
| PROBABLE | One record with ........ | Another record with .... |
|---|---|---|
| PROBABLE 2-1 | NO 4-1 OR 4-2 | 4-1 |
| PROBABLE 2-2 | NO 9-2 | 9-2 |
| PROBABLE 2-3 | NO 5-1 or 5-2 | 5-1 or 5-2 |
| ISCHAEMIC | One record or more with ........ | |
|---|---|---|
| ISCHAEMIC 3-1 | 1-1-1 | TO 1-3-6 EXCLUDING 1-2-6 |
| ISCHAEMIC 3-1 | 4-1 | TO 4-3 |
| ISCHAEMIC 3-3 | 5-1 | TO 5-3 |
| ISCHAEMIC 3-4 | 9-2 | |
FOR Q CODES (1-*-*)
FOR STD (4-*)
FOR T (5-*)
FOR STE (9-*)
FOR SUPPRESSION CODES (VARIOUS)
The program then suppresses the relevant fields or codes in the electrocardiograms in which suppression codes are present.
Code 4 suppresses all fields, codes 1,2,3 suppress STD, T AND STE fields.
Code 2 suppresses the Q fields whose original values were 2-3,2-7,2-8,3-2 or 3 6. Code 1 suppresses the Q fields whose original value was 2-8.
If all the converted Q fields in all the ECGs are 0, and they all have a converted suppression code which is not 0, then the diagnosis is MONICA code 5, UNCODABLE........STOP
DEFINITE.
For all Q comparisons, the first ECG record is used as the baseline unless the Q field is suppressed, when the first record in which it is not suppressed is used. If there is a progression from the first to a subsequent ECG, within a lead group, from converted Q code 0 to converted Q code 2, then the diagnosis is MONICA code 1.1 DEFINITE.......STOP
The program then searches for smaller Q progressions and for simultaneous progression between the first codable and any subsequent ECG of :
BOTH
AND
SO THAT BOTH CHANGES OCCUR BETWEEN THE SAME TWO ECGs
If more than one of these is present then the algorithm awards the lowest code number.
If there are two consecutive ECGs of different dates in which the converted STE field is coded 1 within the same lead group, the program searches for a T progression on three consecutive graphs of different dates, within the same lead group showing the sequence: 0, 3, 3 or 0, 2, 3 or 0, 3, 2 or 0, 2, 2 or 0, 1, 2 or 0, 2, 1 or 1, 3, 3 or 1, 3, 2 or 1, 2, 3 (the algorithm subtracts the code of the first graph from each of the subsequent two and the result is accepted if the value is 1 or more and the sum of these two subtractions is three or more.) MONICA ECG code 1.8 DEFINITE.........STOP
PROBABLE.
The algorithm searches for lesser diagnostic categories in those cases not already diagnosed.
If in any two of the ECGs there is within one lead group an STD field with the value 3 in one graph and 0 or 1 in another the MONICA code is 2.1 PROBABLE ... ...STOP
If in any two of the ECGs there is within one lead group an STE field with the value 0 in one graph and 1 in another the MONICA code is 2.2 PROBABLE....STOP
If in any two of the ECGs there is within one lead group a T field with the value of 2 or 3 in one graph and 0 or 1 in another the MONICA code is 2.3 PROBABLE ......STOP.
As has been demonstrated, the PROBABLE codes are tested for in sequence so that the lowest value is awarded.
ISCHAEMIC
In those cases not already diagnosed :
Any unsuppressed codable Q field greater than 0 gives MONICA code 3.1 ISCHAEMIC ...STOP
Any unsuppressed codable STD field greater than 0 gives MONICA code 3.2 ISCHAEMIC .......STOP
Any unsuppressed T fields greater than 0 gives MONICA code 3.3 ISCHAEMIC..STOP
Any unsuppressed STE fields greater than 0 give MONICA code 3.4 ISCHAEMIC ...STOP
OTHER
If the record is still not diagnosed then the MONICA code is 4 OTHER ....STOP
| 9 | ABSENT ECG |
| 5 | UNCODABLE |
| 1.1 | DEFINITE |
| 1.2 to 1.8 | DEFINITE |
| 2.1 to 2.3 | PROBABLE |
| 3.1 to 3.4 | ISCHAEMIC |
| 4 | OTHER |
The coronary event registration data to be sent to the MDC are specified in the Core Data Transfer Format - Coronary Events, which is appended to this section.
Version 3 of the Acute Coronary Care Record Format was used for the first period of acute coronary care monitoring in all MCCs. At that time such monitoring was to be intermittent and done on 500 consecutive cases near the start and at the end of event registration. The Principal Investigators Meeting in Augsburg in 1988 agreed that centres should, if they could, monitor acute coronary care continuously because it was changing so rapidly and could influence diagnoses through the introduction of thrombolytic therapy, for example.
The present version 6 of the Acute Coronary Care Record Format has used some of the spaces left for Future Interventions to code items that Principal Investigators want included. It should be used on all future coronary event registrations, except those in which the DIACAT is 4. NOTE: It is a modified version of the format circulated with the 1989 Test Case Histories.
It is inevitable that some MCCs will find it very difficult to complete certain items in all cases and that there will also be cases in which virtually no information is available. However, the absence of information does not invalidate a record and records with missing and incomplete information should be forwarded to the Data Centre without preselection. However, it is important that all fields are filled and that codes for inadequate data are used to show where this is so.
When this has been done there should be a complete series of MONICA Coronary registrations for the MCC, with each routine Coronary Event Record linked with an Acute Coronary Care Record, unless the DIACAT is 4. It is important that each MCC has a checking system to ensure that this is so and that the Serial numbers on the two records correspond.
The acute coronary care data to be sent to the MDC are specified in the Core Data Transfer Format - Acute Coronary Care, which is appended to this section.
A list of groupings of drugs for the acute coronary care record is given in Annex 2.
The procedure for correcting errors which have already been submitted to the MDC are described in Part V, Section 1.3.3.
Every suspect event should be issued a serial number by the MCC as early as possible in the identification process, especially in MCCs which register retrospectively. The minimum requirement is that when the MCC begins to collect data on a suspect event, it is provided with a serial number. The serial number consists of seven digits. Each serial number must be unique within each MONICA Reporting Unit and within each register (i.e. stroke register and coronary register). Different MONICA Reporting Units and different registers may use the same serial numbers. The serial numbers within a Reporting Unit and register must be different for different events throughout the ten-year registration period.
Log-books of serial number histories: The MCCs must keep a log-book of the history of every Coronary Serial Number and Stroke Serial Number issued. The items of the Serial Number Inventory Format should be included in this log-book. The serial number histories are used to monitor the data flow and time lag in the event registration.
Correctness of the serial number: The serial number is one of the key items of an event record. The Form Identification, Collaborating Centre Code, Reporting Unit Code and Serial Number are all necessary in order to uniquely identify an event. Each MCC should have some kind of security system to help assure that the serial number is error free. One possibility is to have the last digit of the serial number a check digit which is used to control the correctness of the other digits at least until the individual record has been computerized.
A check digit needs to be calculated when the serial number is issued. It is useful only if this is done correctly. This can be secured by letting a computer generate the serial numbers with the check digits and print the numbers on stickers or labels which are then stuck on the log-books and data collection forms.
Serial number inventory data transfer: Serial number inventory data should be sent to the MDC as instructed in the Coronary Serial Number Inventory Format, which is appended to this section.