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STRESS TESTING
pretest probability of a new diagnosis of coronary
artery disease should be admitted to the hospital for
close monitoring and further observation and exami-
nation. These patients may undergo evaluation and
treatment with an invasive strategy that may include
coronary angiography, or a conservative strategy with
standard medical therapy.
11
Patients who have been appropriately selected
for cardiac stress testing (those with intermediate
pretest probability, nondiagnostic serial EKGs, and
normal serial cardiac biomarkers) should undergo
an appropriate cardiac stress test in the ED, in an
observation unit, or as an outpatient within 2–3 days.
Those with a negative stress test, probably have a low
posttest probability of coronary artery disease, and
may be discharged home with short-term primary
care follow up for further evaluation of their symp-
toms. Those with a positive stress test, probably have
a high posttest probability of coronary artery disease,
and should be admitted to the hospital for further
evaluation and treatment.
11
Patients who present to the ED with chest pain con-
cerning for ACS, who have had a prior normal stress
test, present a disposition challenge for the emergency
physician. Assuming that the patient’s initial evalua-
tion is normal, and that the patient would otherwise
be referred for cardiac stress testing, the physician may
consider whether or not stress testing has a “warranty
period.” For example, is another stress test indicated
if the patient had a normal stress test 1 year ago? In
other words, how long after a negative stress test does
the patient remain at low risk of an adverse cardiac
event such as myocardial infarction or even death?
Unfortunately for the emergency physician, the
medical literature has not been able to establish a
broad-based consensus warranty period for a normal
stress test.
23–26
In general, studies use an adverse event
rate of less than 1% per year to defi ne an acceptable
risk or benign prognosis.
23,24,26
Nevertheless, com-
parison across studies of the duration of a benign
prognosis is diffi cult because of differing study popu-
lations, testing protocols, and follow-up periods with
regard to the normal index test. One review and
meta-analysis indicates that adverse event rates after
normal exercise myocardial perfusion imaging and
normal exercise echocardiography are fewer than
1% throughout an approximately 3-year follow-up
period.
26
This suggests that the warranty period of
normal stress echo and stress myocardial perfusion
Exercise echocardiography has both a sensitiv-
ity and specifi city of 80–90%.
6,18,21
It has a lower
associated cost than nuclear imaging, and can assess
location and extent of heart disease, even with EKG
abnormalities at baseline. However, disadvantages of
this modality are that it is highly operator- and inter-
preter-dependent. Results may be diffi cult to interpret
due to poor image quality in certain patients, such as
those who are obese, or who have underlying heart or
lung disease at baseline.
Myocardial perfusion testing before and after
exercise is generally reported to have a sensitivity of
80–90% and a specifi city of 70–80%.
18,21
Depending
on the isotope and methodology used, this modal-
ity may be the most sensitive cardiac stress test.
18,22
Results are generally reproducible and provide
detailed information regarding location of disease
and overall cardiac function. However, disadvantages
of this modality are that it the most expensive cardiac
stress test, and may not be widely available.
In addition to differences in modality, physicians
must choose whether a patient should exercise (i.e.,
walk on a treadmill or ride a stationary bicycle) or
undergo pharmacologic stress. In general, patients
who are able to do so should exercise. In the case of a
positive test, an exercise test can document the func-
tional capacity at which symptoms occur, and there
are no concerns about possible side effects of stress-
inducing medications. However, in patients who can-
not exercise due to musculoskeletal disease or other
limitations, pharmacologic stress may be indicated.
While pharmacologic stress testing may aid in the
diagnosis of coronary artery disease in patients unable
to exercise, care should be taken to screen patients
who should not receive cardiac agonist medications.
For example, dobutamine may cause dysrythmias,
and dipyridamole should not be given to patients with
severe reactive airway disease.
Disposition
As discussed, patients with a very low or very high
pretest probability of coronary artery disease should
not undergo cardiac stress testing for the diagnosis of
coronary artery disease. Patients with chest pain and
very low pretest probability should undergo evalu-
ation for noncardiac causes of chest pain, and their
disposition depends on the appropriate management
of their noncardiac diagnosis. Patients with very high
CHAPTER 24
stress EKG compared with imaging stress, it is intui-
tive that the warranty period should be shorter.
Summary
The patient discussed at the beginning of this
chapter, a 49-year-old woman with a history sugges-
tive of typical angina, likely has a pretest probability
for coronary artery disease between 50 and 60%.
13,16
The most appropriate initial test in this patient would
be cardiac stress imaging, either with echocardiog-
raphy or myocardial perfusion, depending on local
availability and expertise. Additionally, the emer-
gency physician should make a frank determination
regarding whether the patient can adequately exercise
for the test. A more accurate imaging test would also
may be 2–3 years. However, another study suggests
that the warranty period for stress echo may only be
18 months.
23
Furthermore, patient history likely alters the war-
ranty period of a normal test. In other words, the
duration of a benign prognosis may differ between
individual patients. For example, one study regarding
the warranty period of a normal myocardial perfu-
sion scan suggests that clinical factors (such as diabe-
tes and increasing age) may change the risk of adverse
events over time.
24
Little prospective data exists regarding the warranty
period of exercise EKG testing; nonetheless, at least
one study demonstrates the superior prognostic ability
of stress echocardiography when compared to stress
EKG.
25
In addition, given the decreased sensitivity of
Management Flow Chart for Stress Testing
Stable patient presents with chest pain
Determination of pretest probability of CAD
IntermediateLow
AbnormalNormal
Admint for further
evaluation and
treatment
Discharge with primary
care follow-up
High
Normal initial exam,
EKG, biomarkers
Normal observation period for serial EKGs, biomarkers
Evaluate for other
etiologies of pain
Admit for further eval
Exercise echo for:
– abnormal resting EKG
– local expertise
Exercise myocardial perfusion for:
– abnormal resting EKG
– severe COPD, obesity
Exercise stress EKG for:
– most patients
– normal resting EKG
– able to exercise
Figure 24.1 Management fl ow chart for stress testing.
STRESS TESTING
of low-risk patients with potential acute coronary syn-
dromes. Ann Emerg Med. 2009;53: 295–304.
Lau J, Ioannidis JPA, Balk EM, et al. Diagnosing 6
acute cardiac ischemia in the emergency department:
a systematic review of the accuracy and clinical effect
of current technologies. Ann Emerg Med. 2001;37:
453–460.
Pope JH, Aufderheide TP, Ruthazer R, et al. Missed 7
diagnosis of acute cardiac ischemia in the emergency
department. N Engl J Med. 2000;342:1163–1170.
Heron M. Deaths: leading causes for 2004. 8 Natl Vital
Stat Rep. Nov 20 2007;56(5):1–95.
Bayley MB, Schwartz JS, Shofer FS, et al. The fi nancial 9
burden of emergency department congestion and hos-
pital crowding for chest pain patients awaiting admis-
sion. Ann Emerg Med. 2005;45:110–117.
Antman EM, Anbe DT, Armstrong PW, et al. ACC/10
AHA guidelines for the management of patients with
ST-elevation myocardial infarction: a report of the
American College of Cardiology/American Heart
Association task force on practice guidelines (commit-
tee to revise the 1999 guidelines for the management of
patients with acute myocardial infarction). J Am Coll
Cardiol. 2004;44:e1–211.
Anderson JL, Adams CD, Antman EM, et al. ACC/AHA 11
2007 guidelines for the management of patients with
unstable angina/non-ST-elevation myocardial infarc-
tion: a report of the American College of Cardiology/
American Heart Association task force on practice
guidelines (writing committee to revise the 2002 guide-
lines for the management of patients with unstable
angina/non-ST-elevation myocardial infarction). J Am
Coll Cardiol. 2007;50:e1–157.
Wolfson AB, et al. 12 Harwood-Nuss’ Clinical Practice of
Emergency Medicine. 4th ed. Philadelphia: Lippincott
Williams & Wilkins; 2005:58–61.
Diamond GA, Forrester JS. Analysis of probability as 13
an aid in the clinical diagnosis of coronary-artery dis-
ease. N Engl J Med. 1979;300:1350–1358.
Pryor DB, Harrell FE, Lee KL, et al. Estimating the 14
likelihood of signifi cant coronary artery disease. Am J
Med. 1983;75(5):771–780.
Pryor DB, Shaw L, McCants CB, et al. Value of the 15
history and physical in identifying patients at increased
risk for coronary artery disease. Ann Intern Med.
1993;118:81.
Weiner DA, Ryan TJ, McCabe CH, et al. Exercise 16
stress testing: Correlations among history of angina,
ST-segment response, and prevalence of coronary-
artery disease in the Coronary Artery Surgery Study
(CASS). N Engl J Med. 1979;301(5):230–235.
Patterson RE, Horowitz SF. Importance of epidemi-17
ology and biostatistics in deciding clinical strategies
be useful in diagnosing coronary artery disease in the
setting of an abnormal baseline EKG.
At this point in the case, after a concerning but
indeterminate exercise EKG, the physician had not
defi nitively changed the patient’s posttest risk for
coronary artery disease. The patient still warranted
further testing, and as well, a cardiology consulta-
tion based on the abnormal EKG fi ndings on the
indeterminate stress test. In consultation with the
cardiologist, one reasonable approach would be to
admit the patient for further evaluation of her car-
diac risk and close monitoring while awaiting stress
imaging. Furthermore, based on the ST depres-
sions on her stress EKG, the cardiologist may have
admitted the patient for angiography and an early
invasive treatment strategy.
11
Another reasonable
approach, in consultation with a cardiologist who
will follow the patient closely, would be to discharge
the patient with instructions for rest and return on
Monday (less than 72 hours) for a stress-imaging
test. Thorough and direct communication with the
patient and cardiologist is paramount in ensuring
that the patient will present for and receive close
follow up and further evaluation for her possible
coronary artery disease.
See Figure 24-1.
Dobrzycki S, Baniukiewicz A, Korecki J, et al. Does gas-1
tro-esophageal refl ux provoke the myocardial ischemia
in patients with CAD? Int J Cardiol. 2005;104:67–72.
Smith KS, Papp C. Episodic, postural and blinked 2
angina. BMJ. 1962;II:1425–1430.
Sabia P, Afrookteh A, Touchstone DA, et al. Value of 3
regional wall motion abnormality in the emergency
room diagnosis of acute myocardial infarction: A pro-
spective study using two-dimensional echocardiogra-
phy. Circulation. 1991;84:I85–I92.
Nawar EW, Niska RW, Xu J. 4 National Hospital
Ambulatory Medical Care Survey: 2005 Emergency
Department Summary. Vol No. 386. Hyattsville, MD:
National Center for Health Statistics; 2007.
Hollander JE, Chang AM, Shofer FS, et al. Coronary 5
computed tomographic angiography for rapid discharge
CHAPTER 24
Bangalore S, Yao S, Puthumana J, et al. Incremental 23
prognostic value of stress echocardiography over clini-
cal and stress electrocardiographic variables in patients
with prior myocardial infarction: “warranty time” of
a normal stress echocardiogram. Echocardiography.
2006;23(6):455–464.
Hachamovitch R, Hayes S, Friedman J, et al. 24
Determinants of risk and its temporal variation in
patients with normal stress myocardial perfusion scans:
what is the warranty period of a normal scan? J Am
Coll Cardiol. 2003;41:1329–1340.
Mahenthiran J, Bangalore S, Yao S, et al. Comparison 25
of prognostic value of stress echocardiography ver-
sus stress electrocardiography in patients with
suspected coronary artery disease. Am J Cardiol.
2005;96:628–634.
Metz LD, Beattie M, Hom R, et al. The prognostic 26
value of normal exercise myocardial perfusion imaging
and exercise echocardiography: a meta analysis. J Am
Coll Cardiol. 2007;49:227–237.
for using diagnostic tests: a simplifi ed approach using
examples from coronary artery disease. J Am Coll
Cardiol. 1989;13(7):1653–1665.
Garber AM, Solomon NA. Cost-effectivenes of alterna-18
tive test strategies for the diagnosis of coronary artery
disease. Ann Intern Med. 1999;130:719–728.
Gianrossi R, Detrano R, Mulvihill D, et al. Exercise-19
induced ST depression in the diagnosis of coronary
artery disease: a meta-analysis. Circulation. 1989;80:
87–98.
San Roman JA, Vilacosta I, Castillo JA, et al. Selection 20
of the optimal stress test for the diagnosis of coronary
artery disease. Heart. 1998;80:370–376.
Fleischmann KE, Hunink MGM, Kuntz KM, et al. 21
Exercise echocardiography or exercise SPECT imag-
ing? A meta-analysis of diagnostic test performance.
JAMA. 1998;280:913–920.
Ioannidis JPA, Salem D, Chew PW, et al. Accuracy of 22
imaging techniques in the diagnosis of acute cardiac
ischemia in the emergency department: a meta-analysis.
Ann Emerg Med. 2001;37(5):471–477.
349
Cardiovascular Problems in Emergency Medicine: A discussion-based review, First Edition.
Edited by Shamai A. Grossman and Peter Rosen.
© 2011 John Wiley & Sons, Ltd. Published 2011 by John Wiley & Sons, Ltd.
Coronary computed tomography
J. Tobias Nagurney
1
& David F.M. Brown
2
1
Assistant Professor of Surgery, Division of Emergency Medicine, Harvard Medical School,
Attending Physician and Director of Research, Department of Emergency Medicine,
Massachusetts General Hospital, Boston, Massachusetts, USA
2
Vice Chair, Department of Emergency Medicine, Massachusetts General Hospital,
Associate Professor, Harvard Medical School, Boston, Massachusetts, USA
25
Section I: Case presentation
A 38-year-old man presented to the Emergency Depart-
ment (ED) with left-sided chest pain. The pain began
the prior morning during some exertion, lasted about
15 minutes, and recurred intermittently during the
afternoon and evening. On the day of admission, he
awakened with a similar pain that lasted about an hour
prior to coming to the ED. The pain was dull, nonpleu-
ritic, and nonradiating. There was no associated short-
ness of breath, nausea, or palpitations. There was some
diaphoresis. The patient had no prior history of similar
chest pain, and no known coronary artery disease. His
past medical history was notable for migraine head-
aches that were relieved with Fioricet. He had smoked
about one pack of cigarettes per day for 20 years, did
not use drugs, and worked as a fork lift operator. He
had a positive family history for coronary artery dis-
ease—his father had suffered from a myocardial infarc-
tion (MI) at age 50.
On ED arrival, he was pain free. The vital signs were:
blood pressure 140/85 mmHg, heart rate 80 beats/
min, respiratory rate 12 breaths/min, temperature
98.6˚F, and oxygen saturation 99% on room air. There
was neither jugular venous distention nor bruits. The
breath sounds were clear. The chest wall was non-
tender. The cardiac auscultation revealed a normal S1
and S2 without murmurs, gallops or rubs. The abdo-
men was soft and nontender without masses. The
extremities had no edema. The pulses were 2+ and
symmetric. The EKG demonstrated a normal sinus
rhythm with normal intervals and axis. There were
no ST or T-wave changes suggestive of ischemia.
The patient was placed on oxygen and a cardiac mon-
itor, given 325 mg of aspirin by mouth, and intrave-
nous access was obtained. Laboratory tests showed
normal electrolytes, a normal blood urea nitrogen and
creatinine, and a normal complete blood count. The
cardiac enzymes and troponin levels were normal. A
chest radiograph was normal.
The patient was admitted to observation status for
cardiac monitoring andfurther testing.
Section II: Case discussion
Dr Peter Rosen: I would submit that unless they are
lucky enough to work in an ED that has a chest pain
unit, providers in most institutions would not admit
this patient. There is a divergence of opinion in many
EDs about whether they would hold this patient for
a second set of biomarkers, or whether they would
say that he’s been pain free and the time interval is
long enough, and this fi rst set of cardiac tests is ade-
quate information. Assuming the history was clear
enough for this emergency physician to decide that
this patient needed to be ruled out for an ischemic
CHAPTER 25
350
right question. I think that the right question is, “Is
this an acute coronary syndrome?,” which here should
include a NSTEMI or unstable angina. I disagree with
you as well on the disposition of this patient. I think
that most of our colleagues feel compelled to keep this
patient at least for 6 hours to get a second set of mark-
ers, and then either perform some sort of provocative
or anatomic test, or arrange to have one performed
within 72 hours. This is consistent with the recom-
mendations of the ACC/AHA guidelines for patients
who present to the ED with chest pain.
Dr J. Tobias Nagurney: There are a number of impor-
tant issues here that may infl uence our decision mak-
ing. The fi rst is the age of the patient. If this were a
female patient, we need to know her pre-, peri-, or
postmenopausal status. Here the age is 38, which is
young but would place a man into the cardiac risk age
group. Secondly, the clinical story raises a couple of
red fl ags. We know from the chest pain literature that
two of the more important characteristics that suggest
that chest pain is from an acute coronary syndrome
(ACS) are exertional chest pain and chest pain that
is accompanied with diaphoresis, both of which were
present in this case. Thirdly, even if this patient has
angina pectoris, new-onset angina has a poor prog-
nosis and a high major adverse cardiac event rate.
There are some other clues that this patient has an
unstable cardiac chest pain: it began the day prior for
15 minutes, which is semiprolonged; it occurred inter-
mittently throughout the day, so there is a crescendo
quality to it; on the morning of presentation, while
the patient was at rest, he developed pain upon awak-
ening; and there was not only an episode at rest, but a
prolonged episode. Therefore if this is ischemic pain,
it’s very unstable angina or an infarction that has not
been picked up because the biomarkers were sent too
early. We also know that having a normal initial EKG
in the ED does not completely eliminate the possibil-
ity that the patient is having an acute MI. I don’t think
we have enough data in this patient to conclude that
it’s clearly not ACS.
PR: To be more prudent, you could argue that the
real meaningful pain was on the admission morning,
and that the prior day’s symptoms were a teaser, and
therefore we do need a second set of biomarkers. I
wouldn’t argue strongly with anyone who wanted to
hold the patient for a second set of enzymes, but I still
feel that there are very few EDs who would admit this
coronary syndrome, is there an optimal way to man-
age this patient?
Dr Shamai Grossman: This presentation is typical of
many patients we see in the ED. They present with
chest discomfort. While there are some components
that are suggestive of cardiac ischemia, there are other
components that are not; coupled with a nondiagnos-
tic EKG, we are left with trying to decide: Does the
patient need further ED evaluation, or are we com-
fortable enough that this is not cardiac ischemia that
we are willing to discharge the patient home? The
problem with discharging the patient home is that
we know the literature: the number one source of
malpractice in emergency medicine is missing acute
MIs. If we send home all of these patients, we will cer-
tainly miss some acute MIs. The cautious practitioner
of emergency medicine will recognize these realities,
and act conservatively. Acting conservatively leaves
you with a number of options, one of which might
be admitting the patient to the hospital, one of which
might be admitting the patient to an observation unit,
and another might be doing further evaluation in the
ED with tests such as a coronary CTA.
PR: I would submit that, if your question is, “Is this
patient having a heart attack,” the answer is no. This
patient does not meet criteria for either an ST eleva-
tion or non-ST elevation MI (STEMI or NSTEMI),
and perhaps that is the wrong question. You still
have the possibility that this is an ischemic coronary
syndrome, and that this patient could go home and
fare badly. However, this is not a reason to conclude
that this patient needs to be admitted to the hospital.
I don’t think that there are all that many hospitals
that have beds for a patient like this, nor will many
cardiology services be willing to admit a patient with
a story like this.
DB: I don’t agree that at this point you can conclude
from this workup that this person is not having an
acute MI. The symptoms today lasted an hour, and
then the patient came to the ED. It’s not clear what
the interval is between that hour of symptoms and the
arrival in the ED, but unless it’s 6 or more hours,
the fi rst troponin can be discounted because it takes
at least 4 and probably 6 or 8 hours for a troponin
to become positive after myocardial cell death.
Altogether I don’t think we have excluded an MI suf-
fi ciently in this patient, yet I don’t think that is the
CORONARY COMPUTED TOMOGRAPHY
351
United States, and can potentially be done 24 hours
a day, 7 days a week. The disadvantages of the CT
scan, and there are a number of them, begin with the
literature. Is CT an adequate tool to rule out coronary
artery disease? The studies are ongoing, and we don’t
have a conclusive answer as yet. Some literature sug-
gests that if a patient has less than 50% stenosis by
coronary CT, then that patient is very unlikely to have
acute coronary disease. The idea would seem to be
that if the patient has the CT scan performed while in
the ED, and it doesn’t demonstrate coronary disease,
the patient should not need a stress test, and we can be
reassured that the patient is not having an acute coro-
nary syndrome. We should be further reassured that
if we send that patient home, then we are not sending
a patient home who is going to have an adverse out-
come shortly after we discharge the patient.
PR: I recently saw a paper from Italy which suggested
that CT is actually more accurate than angiography.
Yet, we also know from prior experience that angiog-
raphy can sometimes fool us, and fi nd lesions that
are perhaps not the cause of the patient’s symptoms
thereby forcing our hand into treating them because
we don’t really know what the source of the patient’s
symptoms is. How do you feel about the accuracy of
fi nding a cardiac lesion on CT scan?
DB: Although CT scanning is universally available,
the technology to do a high-resolution coronary CT
scan may not be readily available in many EDs or
hospitals at this point. Even if a coronary CT is avail-
able, having someone who is competent to read the
CT is not necessarily a given. In our group, a select
group of cardiologists and cardiac radiologists read
these scans. This is not to say that it can’t be learned
by a broader group of general CT radiologists just as,
for example, appendicitis has. You might recall that
initially, appendiceal CTs were read by gastrointesti-
nal radiology in our institutions, but are now read
by emergency and general radiologists everywhere.
Having said that, coronary CT scan is more rapidly
available in many institutions then stress testing.
We are also starting to see data that suggest that
coronary CT images do approach the resolution of
conventional coronary angiography, which is the gold
standard for determining whether or not a patient has
coronary artery disease. I sense they will be much more
accurate than conventional stress testing, and perhaps
even more accurate than stress testing with imaging.
patient unless they had no way to set up a stress test
or obtain close follow up within the next 24 hours.
Many departments would hold this patient to get a
second set of biomarkers and a stress test, and if there
were no further symptoms or EKG changes, they
would feel comfortable about dismissing the patient.
Nevertheless, I think there are too many patients who
present like this for us to take the easy path out for
the emergency physician and say, “Just admit the
patient and let cardiology sort it out on the inpatient
service”. In reality, we don’t have enough inpatient
beds, and we don’t have that kind of support from
most cardiologists.
PR: Let’s assume we get a second set of normal bio-
markers, the EKG is unchanged, and he does not have
further symptoms; what would you do next?
JTN: A second negative troponin at the 8-hour mark
has over 95% sensitivity for ruling out an MI. Coupled
with a normal repeat EKG, I would agree with you
that the patient has not had a NSTEMI. However, he
still could have unstable angina. This too needs to be
ruled out, because that can have a poor prognosis,
even short term. I would evaluate this patient with
some sort of risk stratifi cation scheme: an observation
unit may be ideal here to avoid keeping this patient in
the ED for 4–6 more hours while someone is arrang-
ing an exercise tolerance test. If this cannot be done,
I am left with a very diffi cult decision: do I send this
person home and hope he will return for their risk
stratifi cation test in 72 hours or do I admit him to a
regular fl oor?
PR: Is a coronary CT scan appropriate in this patient?
Is it a replacement for the stress test?
SG: We have all alluded to the fact that we are not
truly comfortable saying that this patient’s discomfort
is noncardiac based on the initial presentation, as well
as based on what we know in the literature of these
patients. So we decided that we need to risk stratify
this patient a bit more. One of the options that we just
mentioned is simply to do a second set of cardiac bio-
markers to reinforce that this patient is not having an
acute MI. Even if we do this, we still haven’t answered
the question of whether this patient is having an acute
coronary syndrome or not. We now can utilize a CT
scan, and look directly at the coronary arteries. The
advantage of doing a CT scan is that it is an imaging
modality that is available in just about every ED in the
CHAPTER 25
352
sound like this is such an instance. We have been
searching for many years as to how can we safely
prove these patients negative for ischemia so that we
aren’t going to send them out to drop dead of an isch-
emic coronary syndrome. But how do you defi ne low
probability? Is it several sets of negative biomarkers,
a lack of EKG changes, or is there something else that
identifi es a low-probability patient who will benefi t
from having this negative evidence?
DB: A number of instruments can be used to assist the
physician’s clinical prediction, although I suspect that
most of the time, that assessment is purely based on the
history that is obtained, the EKG, and the physician’s
clinical judgment. But, one could use TIMI risk scores,
which was the approach used in one paper that lim-
ited coronary CT testing to patients with a TIMI risk
scoring of zero or one. One fi nds, when risk-stratifi ed
by a negative coronary CT scan, none of them had
adverse outcomes at 6 months. The ACI TIPI score,
a computer-based algorithm based on the EKG and
some clinical questions, also can help the clinician.
Like TIMI scores, it is not in widespread use. One is
left with the physician’s gestalt, based on risk factors,
the history, and the fi ndings on the EKG. I think we
can assume that cardiac markers are always negative
when this discussion is being had, since any patient
with positive cardiac markers is no longer low risk.
PR: I see CT scanning being used as a screening tool. I
have been told that this has become part of the “exec-
utive workup,” and that once a year if you are over
the age of 50, you ought to have a coronary artery CT
scan. I am not pleased with using it that way because
if you fi nd calcifi cations, I don’t know whether or not
this translates into signifi cant stenosis if the patient is
asymptomatic.
JTN: I agree in general, but that doesn’t mean that
patients shouldn’t get CT scans in the ED. My concern
is that this is a very powerful tool, but is very expen-
sive, and incurs a lot of radiation exposure for the
patient, though the newer CT scanners have decreased
that radiation dose. If we aren’t prudent about who
gets it, as we have seen with other tests that have been
applied to ED populations, it will be used more and
more broadly until just about everyone is getting one.
While today’s discussion is about how can we apply
CT scanning to our own undifferentiated ED patients,
However, when you use the test on the moderate-
to high-risk groups of patients and fi nd plaques with
stenosis, it may not be clear whether that stenosis is
causing the patient’s pain, and so you will have to add
other testing such as sestamibi testing. For the moment,
with low-risk patients primarily being selected for this
test, this would be an unusual result, but if we broaden
the testing population too quickly, we’ll be left with a
lot of patients who will need additional testing, and we
won’t have a more effi cient system.
JTN: The reason that cardiac CT scan is on the table as
a discussion point is because the existing tests haven’t
really fi lled our needs in the ED. Whether an institu-
tion uses a plain exercise tolerance test, a sestamibi
imaging (nuclear imaging), or a rest and stress echo,
they all have limitations of sensitivity and specifi city.
Moreover, they are not generally available 24/7. CT
results have also been shown to add to the differential
information beyond that provided by the risk factors
and chest pain story in an ED. In particular, whether
there is any plaque at all, and if so, how many coronary
artery segments are involved, have both been shown
to have predictive value in diagnosing ACS. The new-
est literature demonstrates that if the CT shows only
plaque but not signifi cant stenosis (less than 50–70%
luminal occlusion, and there are different points of
view on that), these patients are quite safe to go home
and do well for the short (2 weeks) and longer term
(6 months). Nevertheless, there are a lot of exclusion
criteria for utilizing CT scans: for example, atrial
fi brillation, renal insuffi ciency or elevated creatinines,
and patients who are at moderate or high risk of hav-
ing an ACS event. Evaluating this group with a CT
scan is not totally contraindicated, but the data sug-
gest they are not a good group to study. Related to this
are patients with known coronary disease. When there
is a coronary artery calcifi cation, reading the scan is
technically diffi cult.
Another limitation is that across the literature about
10% of these scans have results that are indetermi-
nate. And when you get an indeterminate scan, the
patient ends up getting a second study, a second dose
of radiation, and a second charge (remember these are
not inexpensive tests). These false positives can lead
all the way to cardiac catheterization and generate the
spending of more healthcare dollars.
PR: Almost nowhere in medicine do we have evidence
for a negative test that stands out, and yet this would
CORONARY COMPUTED TOMOGRAPHY
353
JTN: Yes, but I think that question is easy because
women of childbearing age rarely develop acute coro-
nary syndrome. I wouldn’t use a CT scan to look for
coronary disease in a woman of childbearing age. The
good news about all of the literature addressing radia-
tion exposure is that the people who are at higher risk
for radiation exposure are young and female, but the
people who get coronary disease tend to be old and
male. Thus, radiation exposure is not a major concern
to me in implementing this test.
PR: If I understood you correctly, you were using the
CT coronary angiogram as a substitute for an exercise
stress test. Do you think it would be more prudent to
use it only on those patients for whom the stress test
either was not suffi cient, because they couldn’t reach
maximum exercise tolerance or the patients’ obesity,
or some reason that kept them from performing the
stress test? We know that the stress test, when nega-
tive, is not necessarily useful, certainly not as useful
as when it’s positive. I’m not sure that I would trust
a stress test for 6 months, although that may be a
safe timeframe. I don’t think we truly know at what
rate coronary artery disease progresses, and although
6 months sounds reasonable, it may in fact be a shorter
time frame than that.
SG: Given the current literature, I don’t think I would
use a coronary CT scan as my follow-up study for an
indeterminate stress test. That may change as the liter-
ature evolves, but at this point, I think we are talking
about coronary CT scan in the same situations that we
have used a stress test, and perhaps in patient popula-
tions where we can’t do a stress test. So, for instance,
in a patient who returns to an ED who has had an
indeterminate or even a negative stress test and who
presents with the same symptoms, I am still concerned
that the symptoms may be cardiac in etiology. Then,
perhaps doing a different test, such as a coronary CT
scan, will be more useful rather than, as some times
we are forced to do, referring that patient for a coro-
nary angiogram. The other patient population where
it might be useful is in the patient with cocaine-related
chest pain where, perhaps, doing a stress test in an
emergent fashion may not be useful but a coronary
CT might be. The true utility of coronary CT scan is
dependent on literature that is yet to come.
PR: Can coronary CT be used to assist in diagnos-
ing the patient who might have been suffering from
the CT scan is being used by cardiologists to follow
patients with known coronary artery disease. They
are beginning to study not only the anatomy of the
coronary arteries, but actual perfusion imaging with
the CT scan. Cardiologists may actually use this data
in ambulatory patients to track their ejection frac-
tion and their perfusion. The CT scan has dozens of
potential legitimate uses. The concierge aspect that
you mentioned is just one of the abuses.
SG: What do you do with the argument that patients
who receive a CT scan in the ED could have just as
easily had a stress test? The stress test would have
exposed them to no radiation. What do you tell your
patient, and how do you tell your practitioner of
emergency medicine that you should be doing a CT
rather than a stress test?
JTN: I ask them a question, and I tell them two things.
The question I ask the ED practitioner is, “How sen-
sitive do you think an exercise tolerance test is in
an undifferentiated ED population?” Depending on
who I ask, I get different results. There are some data
that exercise stress tests are actually quite insensitive
for coronary artery disease. There is a contrary lit-
erature that shows that a negative stress test in the
ED is associated with an enormous positive or good
prognostic potential for a lack of cardiac events for
six months or even longer. It really depends on what
you believe is the value or the sensitivity in predict-
ing untoward outcomes of the exercise tolerance test.
I would tell the patient, “You can have a stress test
tomorrow morning when it is available. Stay with us
overnight and have that test, which will cost your
health insurance company less money and deliver no
radiation to you, or you can have a test now and pos-
sibly go home in 3 hours. This test may be superior to
the one we would do in the morning, but does expose
you to radiation and costs a great deal more. What
would you prefer?” Only a handful of papers have
begun to address how cardiac CT compares to alter-
native testing like an exercise tolerance test, a nuclear
imaging test, or a resting and stress echocardiogram.
SG: Would you be more inclined to image patients
with CT scan who are at less risk of adverse effects
toward radiation, such as limiting your patient pop-
ulation to patients who are not women of childbear-
ing age?
CHAPTER 25
354
Because all of the diagnostic tools available to the
ED clinician are imperfect, less than 40% of patients
admitted to the inpatient service to ruleout ACS
turn out to have this disease.
1
Conversely, approxi-
mately 2–8% of patients with either acute myocar-
dial infarction or unstable angina are erroneously
discharged home from the ED.
12
Missed myocardial
infarctions represent a major source of medical mal-
practice dollars.
13
In an effort to diagnose ACS accu-
rately and to minimize admissions and inappropriate
discharges, many technologies had been evaluated
in ED populations. Among them are exercise toler-
ance tests, nuclear scans, and echocardiograms.
14–20
However, most of these tests are not available all
hours of the week. A routinely-available test that
would accurately distinguish ED patients with ACS
from those without it would represent an important
diagnostic tool.
Characteristics of an ideal diagnostic test
An ideal diagnostic test would have excellent test
characteristics: sensitivity, specifi city, positive predic-
tive value, negative predictive value, overall accu-
racy, and positive and negative test-likelihood ratios.
It would be safe to perform and require a minimal
amount of time outside the monitored ED environ-
ment. It would be available nights and weekends,
with results reported soon after completion. It would
demonstrate good interrater reliability and be inex-
pensive. At this time, there is no such test, and we
therefore have to accept a degree of imprecision in
any strategy that we pursue. Despite the claims of the
plaintiff bar and those who think we can eliminate all
error from medicine, it is impossible to eliminate all
error in the decisionmaking about possible ischemic
coronary disease.
Cardiac computed tomography (CCT)
angiography: overview
Advances in temporal and spatial resolution of new
multidetector CT scanners allow accurate visualiza-
tion of the coronary arteries in the motion-free state.
Its primary value is to determine whether the coro-
nary arteries contain atherosclerotic plaque, and if so,
whether signifi cant stenosis is present or not. In par-
ticular, the degree of luminal obstruction by plaque
in any of the four major coronary arteries (left main,
coronary artery spasm, or do we really need angiog-
raphy for that?
DB: The answer to your question is not really known,
but I believe that coronary CT scan is not going to be
particularly useful in excluding underlying coronary
vasospasm as the cause for someone’s angina or chest
pain. The CT scan may show you nonobstructive cor-
onary artery disease. You could surmise, I suppose,
that those patients might have coronary vasospasm
that would make non-obstructive disease obstructive
during the period of spasm. I don’t think there’s any
way to know that. With coronary angiography the
opportunity to do some sort of chemical stimulation
test to test for vasospasm is an option, but with CT
scan, I don’t think it is.
Case resolution
The patient received a CT scan of the coronary arter-
ies. All 17 coronary artery segments were clearly visu-
alized. Three segments had a small amount of calcifi ed
plaque, but no lumen was obstructed by more than a
25% cross section. There was no wall motion abnor-
mality. The patient was discharged home to receive
a tailored medical regimen for mild coronary artery
disease and was doing well at 6-month follow-up.
Section III: Concepts
Scope of the problem
A large percentage of patients presenting to EDs
complain of chest pain.
1
Distinguishing those with
an acute myocardial infarction and acute coronary
syndrome from those with noncardiac chest pain is
diffi cult.
2,3
A history of risk factors for coronary dis-
ease may not be helpful.
4
Certain parts of the chest pain story may con-
tribute to establishing a diagnosis, but are neither
sensitive nor specifi c enough to allow providers to
discharge patients directly home from the ED.
5
The
EKG changes that are diagnostic of an acute MI are
both insensitive and nonspecifi c.
6–8
Biomarkers are
time dependent, and the patient may arrive in the ED
too early for them to be helpful.
9
Clinical factors and
laboratory results have been combined in attempts to
predict which patients have ACS, but with varying
success.
10,11