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More Data Needed for Protocol Change
chest Pain Protocol, continued from page 1
chest pain patients to get the risk as low
as possible,” Than explained. “Given that
only 20 to 25 percent have acute myocardial
infarction, that’s a lot of people being
investigated. That, paired with the fact that
hospitals have an immense problem with
overcrowding, is one of the challenges of
the healthcare system for the next decade,
if not longer.” He is director of emergency
medicine research at Christchurch Hospital
in Christchurch, New Zealand.
The Details of ASPECT
Than and his colleagues at 14 emergency
departments in nine countries in the Asia-
Pacific region launched the Asia-Pacific
Evaluation of Chest Pain Trial (ASPECT)
to assess whether a pre-defined protocol
could identify patients presenting to
the emergency department with chest
pain who would be at low risk of harm if
they were discharged early. The protocol’s
POC panel consisted of cardiac troponin I
(cTn), creatine kinase MB (CK-MB), and
myoglobin. Researchers combined biomarker
results with the Thrombolysis in
Myocardial Infarction (TIMI) risk score
and electrocardiograph (ECG) to establish
patient risk.
ASPECT involved 3,582 consecutive
adult patients who reported at least 5 minutes
of chest pain suggestive of ACS. Patients
received normal care, and attending physicians
had access to central lab cTn results
but were blinded to TIMI score and results
from the POC panel, samples for which were
drawn at admission and after 2-hours. The
researchers combined the ASPECT protocol
with medical records and telephone followup
to determine the study’s primary endpoint,
major adverse cardiac events within
30 days after initial presentation.
The POC panel results were considered
positive when cTn was ≥0.05µg/L, CK MB
was ≥4.3 µg/L or had an increase ≥1.6 µg/L
within 2 hours, or myoglobin was ≥108
µg/L or increased ≥25% within 2 hours.
Patients were deemed low risk if they had a
TIMI score of 0, no new ischemic changes
on ECG, and normal results from the POC
biomarker panel, at both admission and
2-hours. The researchers found that 9.8%
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of patients were at low risk and would have
been eligible for early discharge. Following
release from the hospital, a major cardiac
event occurred in three (0.9%) low-risk
patients, giving the protocol a sensitivity
of 99.3%, specificity of 11%, and negative
predictive value of 99.1%.
Practice Changes Desired but Difficult
Observers agreed that a system which
would lead to as many as 10% of suspected
ACS patients being discharged quickly
and safely would have considerable merit.
“There’s overcrowding in emergency departments
in the U.S. and world wide, so
even a nine or 10 percent discharge rate
that wasn’t there before would make a big
difference in work flow,” said Alan Wu,
PhD, director of clinical chemistry and
toxicology at the University of California-
San Francisco.
However, Wu was not alone in cautioning
that as intriguing as the ASPECT results
may be, a 2-hour assessment protocol is
unlikely to be adopted in practice anytime
soon. “It’s not a simple thing to change protocols.
No single study would be the driving
force to elicit such a change, but this will
contribute to it,” he said. “Every institution
would have to look at its own resources,
needs, and turnaround times, and determine
if it would be comfortable with a twohour
rule-out. A lot of hospitals in the U.S.
will not be ready to adopt this today, especially
where the medicolegal aspects are so
different and we don’t have the luxury of
missing an MI.”
Hospitals worldwide adhere to guidelines
on the universal definition of MI issued
in 2007 by the European Society of
Cardiology, American College of Cardiology
Foundation, American Heart Association,
and World Heart Foundation. These
guidelines call for a cTn measurement
exceeding the 99th percentile of a normal
reference population with a coefficient of
variation ≤10% as an element of diagnosing
MI, along with at least one additional criterion:
symptoms or ECG changes indicative
of ischemia; development of pathological Q
waves in the ECG; or imaging evidence of
new loss of viable myocardium or regional
wall motion abnormality. The guidelines
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also note the importance of rising and/or
falling cTn values in discerning MI. Measurements
should be taken at the time of
first assessment and 6–9 hours later to detect
any pattern. CK-MB by mass assay is an
acceptable alternative when cTn values are
not available, according to the guidelines.
Cutting Down Assessment Times
Healthcare systems have adopted various
strategies to adhere to the universal definition
of MI while not keeping chest pain patients
in emergency department beds per se.
For example, many have chest pain or observation
units where they transfer suspected
ACS patients for continued work up.
However, depending on how the units are
staffed and where they’re located, they may
still demand attention and resources from
the emergency department for 6–8 hours,
and in some instances, up to 12 hours.
Widespread adoption of the universal
definition of MI and use of strategies like
observation units reflect how far the fields
of emergency medicine and cardiology
have come over the past three decades in
discerning MI from other sources of chest
pain and moving towards shorter, more efficient
assessment processes, according to
Ezra Amsterdam, MD, associate chief of
cardiovascular medicine at UC Davis Medical
Center in Sacramento, Calif. “There’s
been an evolution over the past 30 years.
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We’ve gone from admitting every adult
patient with chest pain, and putting them
through these rule-out procedures with serial
cardiac enzymes and ECGs over several
days until you finally decided it was OK
to discharge the patient. That’s accelerated
into protocols where a majority of patients
are not admitted, and it’s done safely,” he
explained. “So the ASPECT protocol is not
new per se. What’s new is their systematic
approach to a two-hour assessment.”
An Objective Method
Such a systematic approach to identifying
patients at low risk has been a missing ingredient
in emergency medicine, according
to W. Frank Peacock, MD, vice chair
of emergency medicine at the Cleveland
Clinic Foundation. “Chest pain is the emergency
department’s first or second most
common presentation. The likelihood of
an emergency doctor having a bad outcome
in patients with chest pain occurs in
the first five years of practice, so that tells
you it’s really subjective,” he said. “What
Martin did was to validate an accelerated
diagnostic protocol with completely objective
measures. There’s nothing subjective
about it, and that’s the advantage.” Peacock
helped analyze data and write the ASPECT
report, but no Cleveland Clinic patients
were part of the study.
See chest Pain Protocol, continued on page 8
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