2. INTRODUCTION
Chest pain is one of the most common
presenting symptoms in the emergency
department (ED)
patients encompass a wide spectrum of
underlying diagnosis ranging from
(1) Acute Coronary Syndrome
(2) Non-ACS cardiovascular conditions:
myocarditis/myo-pericarditis
stress-related cardiomyopathy
aortic dissection
pulmonary embolism
(3) non-cardiac cause of chest pain:
gastroesophageal reflux
sepsis
3. ACS
Acute coronary syndrome (ACS) is a
unifying term representing a common end
result, acute myocardial ischemia. It
describes a spectrum of clinical
syndromes ranging from unstable angina
to NSTEMI and STEMI.
Patients presenting with ACS are divided
into those with ST elevation (lasting ≥20
minutes) or new left bundle branch block,
and those with NSTEACS which includes
transient ST elevation (lasting <20
4. Recognizing a patient with ACS is important
because of the life-threatening nature of an
ACS.
It is prudent to have a low threshold in
suspecting a patient with acute chest pain as
potentially having an ACS.
5. PATHOPHYSIOLOGY:
major causes of ACS are
1. Thrombus
2. mechanical obstruction
3. dynamic obstruction
4. Inflammation
5. increased oxygen demand.
The major pathophysiologic mechanism is
rupture or fissuring of an atheromatous plaque
with superimposed thrombus
6.
7.
8. ECG:
cost-effective tool for the initial diagnosis in
patients with chest pain and possible ACS
Limitations:
up to 40%-65% patients with evolving ACS have a
normal or non-diagnostic presenting ECG
baseline ECG changes may be present secondary
to underlying pericarditis, left ventricular
hypertrophy, left bundle branch block, and early
repolarization leading to over-diagnosis of ACS
9. reasons for non diagnostic ecg:
1. small infarct
2. location of infarct - LCX territory
3. collaterals
4. timing of ecg in relation to onset of infarct
patientswith acute myocardial infarction (AMI)
and normal ECG admitted have adverse event
rates of up to 19%
10. CARDIAC BIOMARKERS:
detectable blood levels of these cardiac specific
troponins in patients with ACS are associated
with unfavorable outcomes.
The sensitivity and specificity for standard
troponin assays are as high as 99% and 86%
respectively for detection of AMI within 24 hours
of acute chest pain
11. Limitations:
sensitivity of cardiac troponins is poor within the
first 3 hours of onset of symptoms for the detection
of myocardial infarction and predicting subsequent
major cardiac events.
negative troponin T/ CK-MB does not necessarily
confer a low risk of complication in patients
presenting with acute chest pain.
Reason for –ve cardiac markers: Unstable
Angina
12. Highly sensitive troponin assays:
negative predictive value 3 hours after admission with
chest pain was reported to be 99.6 %
the positive predictive value was reported to be
96.5%, making it a powerful tool for both ruling out or
confirming MI, respectively at 3 hours
13. ACUTE REST MYOCARDIAL
PERFUSION IMAGING (MPI)
first documented use of ARMPI in patient dates
back to 1970s, using planar Tl-201 imaging
14.
15. Sensitivity: 90%-100%
negative predictive value: 99%-100%.
There is a 10% absolute reduction and 20%
relative reduction in the rates of unnecessary
admissions among patients who undergo
MPI in the ED in addition to the usual ED
care as compared with those who only
receive standard care.
16. Thus, ARMPI significantly reduces the overall cost involved
in managing patients with acute chest pain. This cost saving
is primarily due to reduction of unnecessary hospitalization
and limiting further diagnostic procedures including coronary
angiography
17. Limitations:
to detect ischemia on rest MPI at least 3%-5%of
the myocardium must be involved.
In patients with coronary artery spasm the
diagnostic accuracy of ARMPI is limited because
once the vasospasm has resolved there might
be normal or super-normal coronary flow
secondary to reactive hyperemia.
18. 3 hours from cessation of symptoms is
considered the cut off for injection of
radiotracers, as later injections may
significantly underestimate the extent of at
risk myocardium and limit the prognostic
ability of ARMPI.
19. COMPARISON OF ACUTE REST MPI WITH
CLINICAL AND ECG DATA
ARMPI has higher diagnostic accuracy than
clinical and ECG changes in patients
presenting with chest pain and non
diagnostic ECG
SENSITIVIT SPECIFICITY PPV for adverse cardiac
Y events
ARMPI 94% 83% 85%
CLINICAL DATA + 88% 37% 45%
ECG
ECG 35% 74%
20. COMPARISON OF ACUTE REST MPI WITH
CARDIAC BIOMARKERS
Sensitivity Specificity
ARMPI 73% 93%
c Tn T 17% 100%
CK MB 4% 93%
Ann Emerg Med 1999;33:639-645
21. Advent of high sensitive troponins has
significantly improved the diagnostic
accuracy of cardiac biomarkers and offers
the opportunity for very early diagnosis of an
ACS
Currently, there are limited data on direct
comparison of hs-troponins and ARMPI
22. ACC/AHA/ASNC GUIDELINES FOR ARMPI FOR
CHEST PAIN EVALUATION
Current guidelines recommend use of ARMPI as a
Class 1, Level of evidence A indication for
assessment of myocardial risk in patients with
suspected ACS
23. STRESS OR REST MPI FOR ACUTE CHEST PAIN
29 mths. follow up of patients, who had
Stress SPECT within 24 hours of admission
in ED, showed that patients with an abnormal
SPECT finding had a significantly higher rate
of cardiac events compared to those with
normal imaging (40%vs 1.6%)
Nabi F, Chang SM, Xu J, et al: Assessing risk in
acute chest pain: The value of stress myocardial
perfusion imaging in patients admitted through the
emergency department. J Nucl Cardiol 2012;19: 233-243
24. Pharmacologic stress allows for the very
early assessment of patients after ACS and
is so indicated in the appropriate use criteria.
25.
26. Score 7–9 : Appropriate test for specific indication (test is generally acceptable and is a
reasonable approach for the indication).
Score 4 – 6 : Uncertain for specific indication (test may be generally acceptable and
maybe a reasonable approach for the indication).
Score 1–3 : Inappropriate test for that indication (testis not generally acceptable and is
not a reasonable approach for the indication)
JACC Vol. 53, No. 23, 2009
27.
28. OTHER NUCLEAR CARDIOLOGY
METHODS
PET:
ina retrospective study done on more than 7000
patients presenting to the ED with chest pain,
92.5%of patients with a positive rest or stress
PET scan were eventually diagnosed with ACS
Currently, there are no data available on the
utility of rest only PET scans in acute chest pain
patients.
29. Fatty Acid Imaging:
free fatty acids are preferentially utilized to
produce ATP, however ischemia causes a shift
from fatty acid metabolism to glucose utilization.
This metabolic derangement may persist long
after the resolution of ischemia, a phenomenon
described as ISCHEMIC MEMORY
15-(p-Iodophenyl)-3-R,S methyl pentadecanoic
acid (BMIPP) is a iodinated branch-chain fatty
acid, with high uptake and long retention in the
myocardium
30. sensitivityand specificity of BMIPP SPECT
imaging performed within 48 hours of chest pain,
towards diagnosing obstructive CAD was
reported to be 74%and 92%respectively
In addition, in patients with CAD detected both
on BMIPP and tetrofosmin SPECT, the extent
and severity score was higher with BMIPP as
compared with the tetrofosmin MPI.
31. BMIPP is beneficial for detecting significant CAD
in patients who have negative initial tetrofosmin
SPECT and are unable to undergo provocative
test due to age or unstable symptoms for
detection of ischemia
BMIPP sensitivity is maintained up to 30 hours
after symptoms resolution. This extended time
window for detection of ischemia has a
potentially important clinical advantage for
evaluation of patients with suspected ACS, who
present long after their symptoms have resolved.
32. Immunoscintigraphy:
Indium-111-labeled antimyosin has been
shown to be highly sensitive in detecting Q-wave
and non–Q-wave infarcts.
However, slow clearance of this agent from the
blood pool does not permit imaging earlier than
18 hours after administration, thereby limiting
the usefulness of this agent in evaluating acute
chest pain
33. Tc-99m-labeled annexin-V binds to the plasma
membrane of myocytes undergoing apoptosis
due to infarction or repetitive ischemia
excellent co-localization with sestamibi in areas
of acute injury, and interpretable images can be
acquired within 4 hours of injection
34. Tc-99m–labeled glucarate binds to nuclear
histones exposed in recently damaged myocytes
There is early visualization of both reperfused and
nonreperfused infarcts with in vivo imaging with lack of
accumulation in ischemia or chronic infarction.
These characteristics, along with a short biologic half-
life, favorable target-to-background ratio, and rapid
blood pool clearance, make this imaging agent ideal for
detecting acute infarction in ED patients who have chest
pain
35.
36. REFERENCES
Ghatak A, Hendel RC. Role of Imaging for Acute Chest
Pain Syndromes. Semin Nucl Med 2013; 43:71-81
ACCF/ASNC/ACR/AHA/ASE/SCCT/SCMR/SNM 2009
Appropriate Use Criteria for Cardiac Radionuclide
Imaging. JACC 2009;53: 2201-29.
ACC/AHA/ASNC Guidelines for the Clinical Use of
Cardiac Radionuclide Imaging—Executive Summary.
Circulation2003;108:1404-1418.
Braunwald's Heart Disease: A Textbook of Cardiovascular
Medicine. 9th edition
Topol. Textbook of Cardiovascular Medicine, 3rd Edition
Radionuclide imaging in acute coronary syndromes .
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