Abstract The aims of this study were to investigate if the acute myocardial infarction (MI)    (SE 77.6%  and SP 93.9%.). All attempts at extending the Uni-G criteria resulted in a decrease in SP

Elaine N Clark

Maria Sejersten

Peter Clemmensen

Peter W Macfarlane

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Evaluating Enhancing the Acute Myocardial Infarction Criteria in the Glasgow 
Electrocardiogram Analysis Program by Including ST Depression 
Elaine N Clark
1
, Maria Sejersten
2
, Peter Clemmensen
2
, Peter W Macfarlane
1 
1
University of Glasgow, UK 
2
Copenhagen University Hospital Rigshospitalet, Denmark 
Abstract 
The aims of this study were to investigate if the acute 
myocardial infarction (MI) criteria in the University of 
Glasgow ECG analysis program (Uni-G) could be 
enhanced by including new lead pairings and to explore 
alternative criteria based on STEMI equivalence. 
912 12-lead ECGs were recorded in ambulances on 
patients with a suspected acute coronary syndrome. The 
ACC/ESC and the Uni-G criteria were modified to 
include pairings {III,-aVL}, {-III,aVL}, and   {-V2,-V3}. 
Using the hospital discharge diagnosis as the gold 
standard, the modified criteria were evaluated. 
Significant changes in sensitivity (SE) and specificity (SP) 
were evident using the modified ACC/ESC criteria: SE 
from 72.1% to 75.4% (p=0.002); SP from 88.1% to 
86.6% (p=0.004). The current Uni-G criteria gave better 
results than the modified ACC/ESC criteria (SE 77.6% 
and SP 93.9%.). All attempts at extending the Uni-G 
criteria resulted in a decrease in SP. 
 
1. Introduction 
The accurate diagnosis of ST elevation myocardial 
infarction (STEMI) is of critical importance when 
determining the treatment of patients presenting with 
suspected acute coronary syndrome (ACS) [1]. The 
criteria for STEMI as defined by the American College of 
Cardiology (ACC) and the European Society of 
Cardiology (ESC) et al  use ST elevation in two 
contiguous leads from the standard 12-lead 
electrocardiogram (ECG) [2,3]. There has been concern 
that the sensitivity of the ACC/ESC criteria is low. 
Various efforts have been made to enhance the criteria 
and, indeed, in the University of Glasgow ECG analysis 
program (Uni-G) [4], extending the ACC/ESC criteria by 
incorporating age and sex dependent criteria has resulted 
in improved performance [5]. 
A criticism of the 12-lead ECG is that it does not give 
enough information on some areas of the heart – in 
particular of the postero-lateral wall.  Additional lead 
placements have been investigated [6]. Other 
investigators have looked at the possibility of using the 
basic 9 standard electrode positions to produce a 24-lead 
ECG [7,8], which, in addition to the standard 12 leads, 
includes a further 12 leads obtained by inverting the 
standard 12 leads. Modified ACC/ESC criteria using new 
lead pairings have been tested on small populations and it 
has been found that the sensitivity of the STEMI 
diagnosis improved [9, 10]. In particular, Wang et al [10] 
found that, by adding 3 new pairings of contiguous leads, 
the sensitivity improved without loss of specificity on a 
population of 116 patients. The authors of these two 
studies recommended that the extended criteria should be 
tested on larger populations of patients with suspected 
ACS. 
The main aim of the present study was to evaluate the 
effect of extending the ACC/ESC criteria to include the 
new lead pairings (aVL,-III; -aVL,III and -V2,-V3) on a 
data set of 912 pre-hospital ECGs. The second aim was to 
evaluate extending the age and sex dependent STEMI 
criteria used in the Uni-G program in the same way. The 
third aim was to explore alternative potential 
enhancements to the Uni-G program criteria based on 
using ST depression, i.e. using STEMI equivalence. 
 
2. Methods 
912 prehospital ECGs recorded in ambulances were 
obtained from patients with suspected ACS in Zealand, 
Denmark. The method of collection of data and the use of 
the discharge diagnosis as the gold-standard for the 
presence of STEMI have previously been described [11]. 
406 ECGs were randomly allocated to a training set and 
506 to a test set. The purpose of these sets was to allow 
development of new enhancements to the STEMI criteria 
using the training set and objective evaluation using the 
test set. The training set consisted of 274 males and 132 
females, mean age 65.4±13.2 years. The test set consisted 
of 327 males and 179 females, mean age 65.4±14.4 years. 
The training set was run using both the ACC/ESC 
criteria and the Uni-G program criteria. Sensitivity (SE) 
and specificity (SP) values were obtained. The ACC/ESC 
criteria were interpreted as ST > a threshold in any two 
contiguous leads in the limb leads aVL, I, -aVR, II, aVF, 
III or in chest leads V1 to V6. The ACC/ESC criteria 
ISSN 0276−6574 29 Computing in Cardiology 2010;37:29−32.
from 2000 [2] and 2007 [3] were both evaluated. The 
former uses a threshold of 0.2mV in leads V1, V2, V3 
and 0.1mV in all other leads. The latter uses a threshold 
of 0.2mV in men and 0.15mV in women in leads V2 and 
V3 and 0.1mV in all other leads. The Uni-G program uses 
continuous equations to set the upper limits of normal ST 
amplitudes depending on age and gender [4]. There are 
therefore two different equations for each lead. 
All sets of criteria were modified to include checking 
for ST elevation greater than or equal to 0.1mV in extra 
paired leads {III,-aVL}, {-III,aVL} and {-V2,-V3}, with 
corresponding horizontal or up-sloping ST segment. 
ECGs that were diagnosed as Left Bundle Branch Block 
(LBBB) were not classified as STEMI equivalent. ECGs 
that satisfied the criteria in the pairs {III,-aVL} or {-V2,-
V3} that were also diagnosed as Right Bundle Branch 
Block (RBBB) were not classified as STEMI equivalent. 
The 406 ECGs were re-analysed using these modified 
criteria and the corresponding SEs and SPs noted. The 
effect of reducing the threshold for {-V2,-V3} to 0.05mV 
as in the guidelines for STEMI [2] was measured. 
The amplitude at the J point for each of the standard 12 
leads, as measured by the program, was output to a 
spreadsheet. Visual inspection of these amplitudes was 
used to identify ECGs that displayed STEMI equivalence, 
and to develop new criteria. 
Different criteria for marked ST depression were 
evaluated on the training set. If the criteria were met and 
there was no relevant conduction defect, then one of two 
statements was output, e.g. “Marked anteroseptal ST 
depression, CONSIDER ACUTE INFARCT” or “Marked 
anteroseptal ST depression accompanies the infarct”. The 
latter statement was printed if an acute ST elevation 
infarct was detected in another wall. The set of criteria 
that gave the best results against the final diagnosis was 
selected and then evaluated on the test set. 
Finally, the SEs and SPs with and without the new 
pairings for ACC/ESC criteria and the Uni-G program 
were obtained for the complete set of 912 ECGs. 
The SE and SP values were compared using 
McNemar’s test. The statistical package used was SPSS 
(version 15; SPSS Inc, Chicago, Illinois). The level of 
significance was set at p < 0.05. 
 
3. Results 
For the training set, adding the new pairings to the 
2000 ACC/ESC criteria resulted in a significant change of 
SE from 66.4% to 70.6% (p=0.031) and an insignificant 
change in SP from 89% to 87% (p=0.063). The SEs and 
SPs for each of the additional pairings and for the 
combination of the 3 new pairings are given in Table 1. 
 
 
 
 
Table 1. SEs and SPs for new pairings based on the 
training set. 
 
 
Modifying the threshold for -V2 and -V3 to be 0.05mV 
improved SE to 73.4%, but SP decreased to 85.9%. 
Adding the new pairings to the 2007 ACC/ESC criteria 
resulted in an insignificant change of SE from 69.2% to 
72.7% (p=0.063) and SP from 85.6% to 83.7% (p=0.063). 
It was decided to use the 2000 criteria for the rest of the 
analysis as the specificity was higher than for the 2007 
criteria and as these criteria were used by Martin et al [9]. 
The criteria in the Uni-G program already included the 
pairing {III, -aVL}. The criteria were extended for the 
other 2 new pairings. The results for the training set were 
not statistically significant. SE changed from 74.8% to 
75.5%, and SP changed from 93.9% to 93.5%. 
For the complete dataset, adding the new pairings to 
the ACC/ESC criteria gave statistically significant 
changes. There was an increase in SE and decrease in SP 
(Table 2).  
 
Table 2. SEs and SPs for ACC/ESC 2000 criteria plus 
new pairings for the complete set of 912 cases. 
 
 ACC/ESC ACC/ESC 
with new 
pairings 
P value 
SE(%) 72.1 75.4 0.002 
SP(%) 88.1 86.6 0.004 
 
Adding the two pairings {-III, aVL} and {-V2, -V3} to 
the criteria in the Uni-G program did not result in 
significant results (Table 3). 
 
Table 3. SEs and SPs for Uni-G program plus new 
pairings for the complete set of 912 cases. 
 
 Uni-G Uni-G with 
new 
pairings 
P value 
SE(%) 77.6 78.3 0.5 
SP(%) 93.9 93.2 0.125 
 
 
 
 
 
 
 ACC 
/ESC 
With 
-V2 
-V3 
With 
-III 
aVL 
With 
III 
With 
 3 new 
pairings-aVL 
SE(%) 66.4 67.8 67.8 69.2 70.6 
SP(%) 89 88.5 89 87.5 87 
30
Out of the 912 cases in the data set, there were only 17 
which met the STEMI equivalence criteria in the new 
pairings but which did not meet the ACC/ESC ST 
elevation criteria and which were not diagnosed as LBBB 
or RBBB (Figure 1). 8 of these 17 had ST elevation levels 
reaching the ACC/ESC limits but also exhibited an 
intraventricular conduction defect. So only 9/912 cases 
met the STEMI equivalence criteria and did not meet 
ACC/ESC ST elevation criteria. 
 
Figure 1. Representation of proportions of cases with ST  
elevation in the new pairings. 
 
7 RBBB
15 LBBB
8 cases 
9 cases 
126 cases 
which 
meet 
ACC/ESC 
criteria
747 cases 
no  ST 
elevation
in the new 
pairings  
9 cases with ST elevation in new pairings and not in
conventional pairings
8 cases with ST elevation in both new and conventional
pairings,      but IVCD
 
 
 
 
 
Different criteria for marked anteroseptal, inferior and 
lateral ST depression were evaluated on the training set.  
The presence of a “Marked ST depression, CONSIDER 
ACUTE INFARCT” statement was used to indicate 
STEMI equivalence MI. The best result obtained was 3 
more true positive results. SE increased from 74.8% to 
76.9% (p=0.25) with no change to SP (93.9%).  However, 
evaluating the criteria for the test set gave one more false 
positive result. So for the test set, SE was unchanged 
(80.1%) and SP decreased from 93.2% to 92.9% 
(p=0.25). 
The following figures 2 and 3 show ECGs with marked 
ST depression as well as ST elevation. In the tracing 
shown in figure 2, when using the new marked ST 
depression criteria, inferior ST depression is reported. ST 
elevation in leads –III and aVL is evident but the ST 
elevation in lead aVL was measured as 92 microvolts and 
so below the required threshold for the new pairings. In 
the tracing in figure 3, a STEMI was reported by the Uni-
G program due to the ST elevation in leads I and aVL. 
The new ST depression criteria result in an additional 
report of marked ST depression in the anteroseptal leads. 
 
Figure 2 This ECG was reported as septal infarct. There is 
also marked inferior ST depression.. The patient was sent 
for primary percutaneous coronary intervention, and the 
discharge diagnosis was STEMI.  
 
 
 
Figure 3. An example of ST depression in leads V1-V3 
accompanying ST elevation in the lateral leads. The 
automated report was lateral infarct. The patient was 
admitted to a local hospital and later transferred for pPCI. 
 
.  
 
31
4. Discussion 
In this study of 912 patients, the use of the new lead 
pairings gave a small but significant improvement in SE 
when using the ACC/ESC 2000 criteria along with a 
significant decrease in SP. We did not observe the same 
degree of improvement in detection of STEMI that had 
been found in previous studies when STEMI equivalence 
criteria had been used. This may be due to a number of 
factors, e.g. different populations, both in size and 
location, and different settings. One major difference 
between this study and that by Martin et al [9] is in the 
method used to determine if a STEMI had occurred. In 
our study, we used the discharge diagnosis as the gold 
standard. Martin et al used contrast enhanced MRI, and 
the presence of delayed hyperenhancement as evidence of 
infarction.  
A factor to be considered when interpreting the results 
is that the physicians who were reading the ambulance 
ECGs were most likely using the 2000 guidelines for 
detection of a STEMI to determine which patients should 
be admitted for pPCI. They were not using STEMI 
equivalence in their criteria. 
However, the main observation was that there was 
little evidence of ECGs with STEMI equivalence only. 
Less than 0.02% of ECGs met that criterion. The different 
findings may be due to the timing of the ECG, i.e. in our 
study the pre-hospital ECG was used and in the study by 
Martin et al [9] the admission ECG was used. Another 
possible explanation is that, in the latter study, there was 
a significantly longer delay from time of symptom onset 
until the initial ECG in the group showing STEMI 
equivalence than in the group with ST elevation. The time 
from symptom onset was not available in our study. 
Reciprocal ST segment depression is said to be a 
highly sensitive indicator of acute MI [12] and it was 
considered worthwhile to modify the Uni-G program 
criteria for reporting ST depression both stand-alone and 
reciprocal to an acute infarct in another site to improve 
the quality of the reporting. This is in accordance with the 
possibility considered by Gettes of modifying algorithms 
and statements to recognize ECG changes related to 
transmural ischemia [13]. 
 
5. Conclusion 
The current Uni-G program gave better results in this 
study than the expanded ACC/ESC criteria. All attempts 
at extending the Uni-G criteria resulted in a decrease in 
SP. It may not be possible to greatly improve the 
diagnosis of STEMI using the 12 lead ECG and hence it 
may be necessary to record additional leads to obtain a 
more comprehensive view.  
 
 
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Address for correspondence. 
 
Elaine Clark 
Electrocardiology Section, 
Level 1, QEB, Royal Infirmary, 
10 Alexandra Parade, 
Glasgow G31 2ER 
Scotland, UK 
 
elaine.clark@glasgow.ac.uk 
32


Evaluating Enhancing the Acute Myocardial Infarction Criteria in the Glasgow Electrocardiogram Analysis Program by Including ST Depression

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Evaluating Enhancing the Acute Myocardial Infarction Criteria in the Glasgow Electrocardiogram Analysis Program by Including ST Depression

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