1258
ST-SEGMENT ELEVATION
Brady et al. • INTERPRETATION OF ST-SEGMENT ELEVATION
T
ABLE 1. Emergency Physicians’ (EPs’) Electrocardiogram
ECGs or past medical records provided the impor-
tant clinical information that enabled the EPs to
arrive at the correct diagnosis; similar rates of
such misidentification have been described else-
where with aneurysmal STE.5
(ECG) Interpretation Concerning ST-segment Elevation
Relative to the Cardiologist Interpretation (Considered to Be
the Standard for Diagnosis)
EP Interpretation
ECG Syndrome
(Cause of ST-segment
Elevation)
(Number Correct/Number Total
of Same Reading)
The BER pattern was the second most fre-
quently misinterpreted STE entity—in a total of
three cases, two were initially noted to represent
pericarditis and one AMI. The incorrect diagnosis
of BER as pericarditis, while troublesome, did not
subject the patients to significant, unnecessary
therapeutic maneuvers. More concerning, the ini-
tial misdiagnosis of AMI in the BER patient could
certainly subject the patient to not only unneces-
sary admission but also unwanted, potentially
dangerous therapies such as thrombolysis; fortu-
nately, none occurred in this review. Concerning
BER, these diagnostic difficulties have been en-
countered in other instances. For example,
Sharkey et al.5 has noted a 30% rate of incorrect
thrombolysis among patients with non-AMI STE
who incorrectly receive a thrombolytic agent; fur-
thermore, the electrocardiographic distinction be-
tween acute myopericarditis and BER is notori-
ously difficult at times.9
[% Correct]
Aneurysm
NSIVCD*
3/5 [60%]
8/10 [80%]
22/25 [90%]
29/31 [94%]
49/51 [96%]
30/31 [97%]
10/10 [100%]
2/2 [100%]
2/2 [100%]
Benign early repolarization
Acute myocardial infarction
Left ventricular hypertrophy
Left bundle branch block
Right bundle branch block
Acute pericarditis
Paced rhythm
*NSIVCD = nonspecific intraventricular conduction delay.
pretation was used. In addition, initial and final
ECG interpretations were compared.
RESULTS
Two hundred two patients had STEs. The rate of
electrocardiographic STE misinterpretation was
12 of 202 (5.9%). The most frequently misdiag-
nosed form of STE was BER in three cases; two
were initially noted to represent pericarditis and
one was diagnosed as an AMI. The LVA pattern
was the second most frequently misinterpreted
STE entity, with two of a total of five cases thought
to represent AMI. ST-segment elevation resulting
from actual AMI was initially incorrectly noted to
be noninfarction in etiology in two cases, one pa-
tient with BER and one with LVH. Agreement be-
tween the EP and cardiologist electrocardiographic
interpretations regarding the cause of STE is de-
picted in Table 1. Table 2 lists the incorrect initial
ECG diagnoses relative to the final, correct diag-
nosis. No patient without the ultimate diagnosis of
AMI who was initially misdiagnosed received
acute revascularization therapy.
ST-segment elevation resulting from actual
AMI was initially incorrectly noted to be nonin-
farction in etiology in two cases. In both instances,
the initial, upsloping portion of the ST segment
was concave, suggesting a noninfarction cause of
the ST-segment waveform abnormality. One pa-
tient was thought to have BER on the ECG, while
the second was incorrectly noted to have LVH-
related STE. In most cases of AMI, the initial up-
sloping portion of the ST segment usually is either
convex or flat; if the STE is flat, it may be either
horizontally or obliquely so. Conversely, concave
STE suggests a noninfarction cause of the wave-
form abnormality. An analysis of the ST-segment
waveform may be particularly helpful in distin-
guishing among the various causes of STE and
identifying the AMI case. This technique uses the
morphology of the initial portion of the ST seg-
ment/T wave. This portion of the cardiac electrical
cycle is defined as beginning at the J point and
ending at the apex of the T wave. The use of this
STE waveform analysis in ED chest pain patients
DISCUSSION
When initial misdiagnoses were investigated in increased the sensitivity and positive predictive
our study, several concerning findings were noted. value for correct electrocardiographic diagnosis of
The initial incorrect interpretation of AMI in non- AMI markedly.3 This morphologic observation
infarction situations was encountered; the mis- should be used only as a guideline. As with most
identification of non-AMI when myocardial infarc- guidelines, it is not infallible; patients with STE
tion was, in fact, present was also seen. The most due to AMI may have concavity of this portion of
frequently misdiagnosed form of STE in this study the waveform.9
population was LVA, for which two of 5 cases were
Left ventricular hypertrophy and LBBB pro-
believed to represent AMI. Upon additional clinical duced STE, which initially suggested the electro-
investigation, other noninfarction diagnoses were cardiographic diagnosis of AMI. In this study pop-
made; undoubtedly, the review of either previous ulation, LVH was misinterpreted as AMI in two