ACADEMIC EMERGENCY MEDICINE • April 2001, Volume 8, Number 4
359
terior wall myocardial infarctions. In most cases,
LIMITATIONS AND FUTURE QUESTIONS
the LVA is manifested electrocardiographically by
varying degrees of STE, which may be difficult to
distinguish from ST-segment changes due to AMI
—particularly in the chest pain patient with
known past myocardial infarction.19 In this hypo-
thetical model, it is not surprising that this partic-
ular example of LVA is misidentified as AMI. Of
particular concern, many EPs in the study would
have offered a thrombolytic agent to the patient for
a presumed AMI. In a real-time interpretation of
the ECG, the EP is able to use additional tools as
to etiology of the STE—such as other historical
features, the examination, and other diagnostic
studies; this issue is true for all instances of mis-
interpretation in this study. This additional infor-
mation likely explains the relative infrequency of
this particular pattern among reports of incorrect
electrocardiographic diagnosis of acute myocardial
infarction.
The second most frequently misinterpreted
STE pattern in this study involved AMI (Fig. 2) of
the lateral wall with an atypical, or concave, STE
morphology. In the majority of patients with AMI,
the initial upsloping portion of the ST segment
usually is either convex or flat; if the STE is flat,
it may be either horizontally or obliquely so. Con-
versely, patients with non-infarctional STE tend to
have a concave morphology of the waveform. This
morphologic observation should only be used as a
guideline. As with most guidelines, it is not infal-
lible; patients with STE due to AMI may demon-
strate concavity of this portion of the waveform.8
This morphologic guide would also have not as-
sisted the EPs in this particular case due to the
concavity of the STE.
Benign early repolarization (Fig. 11) and acute
pericarditis (Fig. 3) patterns were the next most
commonly misdiagnosed STE patterns in this
study EP population. Both electrocardiographic en-
tities may present with pronounced changes, in-
cluding prominent T waves and obvious STE. In
fact, these two electrocardiographic diagnoses are
often difficult to distinguish from one another as
well as from AMI.19,20 In this study, these patterns
were treated with thrombolytic agent frequently—
which can certainly cause significant morbidity
particularly in the pericarditis patient scenario.
Left ventricular hypertrophy and LBBB produced
STE, which incorrectly suggested the electrocar-
diographic diagnosis of AMI to the study physi-
cians. These two patterns are well known to hinder
the diagnosis of AMI via ECG—both as masquer-
ading and obscuring factors—and have been noted
to cause similar diagnostic confusion in other sit-
uations.8,10,19 Unfortunately, the LBBB pattern
This study is limited by several issues, primarily
involving study design. First, the questionnaire
structure of the study itself is a hypothetical, con-
trived situation—highly artificial—and very much
unlike the actual ED encounter. In a real-time in-
terpretation of the ECG, the EP has numerous
other diagnostic tools that may assist in arriving
at the correct etiology of the STE, such as an ex-
panded history, past medical history, the physical
examination, both prior and serial ECGs, various
other diagnostic studies, and consultants. Clearly,
the patient’s history and physical examination are
of particular value in reaching the appropriate di-
agnosis, both clinical and electrocardiographic.
The chest pain patient with STE who appears pale
and diaphoretic is likely experiencing an acute cor-
onary ischemic event. Conversely, a complaint of
chest pain, fully investigated by additional ques-
tions in the history and suggestive of a non-ische-
mic diagnosis, also assists the EP in the electro-
cardiographic interpretation. Essentially, the ECG
is a test that must be interpreted in the context of
that particular patient event. The study design
clearly removed this option from the participants.
Furthermore, past ECGs are invaluable, if avail-
able, in the evaluation of the chest pain patient
with STE. The EP who evaluates the chest pain
patient with a history of LVA and electrocardio-
graphic STE clearly is assisted by past ECGs. Per-
haps the lack of past ECGs in this study model
accounts for the high rate of misinterpretation in
the LVA patient scenario. Last, serial ECGs,
whether via repeat ECGs or ST-segment trend
monitoring, would also have assisted the EP in dis-
tinguishing between ischemic and non-ischemic
causes of STE.
The EP study population comprised a conven-
ience sample of physicians. In that these physi-
cians were attending a lecture on the electrocar-
diographic diagnosis of AMI, they may have
represented either a group of physicians with a
particular interest in the ECG or, alternatively, a
subset of EPs with a knowledge deficit in the topic.
In either instance, this group of EPs may not rep-
resent the EP pool in general.
The major future issue involves educational
programs aimed at EP instruction regarding elec-
trocardiography. The fact that attending-level EPs
fared better in terms of correct diagnosis with cer-
tain patterns may suggest that additional educa-
tion (and experience) may improve a physician’s di-
agnostic ability with respect to the ECG and STE.
Structured educational programs may have an im-
pact on correct diagnosis in resident-level EPs.
with electrocardiographic AMI was also misdiag- Emergency physician electrocardiographic educa-
nosed as non-AMI.
tion must focus on the proper identification of