Sixty-Four-Slice Computed
Tomography of the Coronary
Arteries: Cost-Effectiveness
Analysis of Patients Presenting to
the ED with Low Risk Chest Pain
Rahul K. Khare, MD
Institute for Healthcare Studies
Department of Emergency Medicine
Feinberg School of Medicine
Northwestern University
rkhare@northwestern.edu
1
2
Chest Pain In the Emergency
Department

“Chest Pain”
Most common Emergency Department
diagnosis in patients 50 years or older
 Over 50% will not be diagnosed with coronary
artery disease


The identification of chest pain patients
with significant coronary artery disease
remains a challenge
3
Strategies



One strategy is the use of chest pain
observation units (OU) in the ED
EDs have developed OUs to efficiently and
safely manage low risk chest pain patients
with serial cardiac enzymes and subsequent
cardiac stress testing
There is still a significant cost and time
investment involved
4
Current Management of LowRisk Chest Pain in the ED



54 year old male complains of chest pain
Patient smokes & has high blood pressure
ED course
Near normal ECG
 First cardiac enzymes are within normal
 He is now chest pain free

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Current Strategy

7.7% of missed myocardial infarctions die


You cannot send this patient home
Admit to the observation unit
Continuous telemetry monitoring
 Serial cardiac enzymes
 Either a stress echo or stress ECG

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New Potential Management



64-slice multidetector computed
tomography of the coronary arteries
(MDCT) - new modality for evaluation of
CAD
Some advocate use of MDCT in the ED for
low risk chest pain patients as an
alternative to Observation Unit and stress
testing.
Not current standard of care in the ED
setting
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Rationale


MDCT may become a first-line screening
instrument for detecting significant CAD in
low risk patients presenting to the ED with
chest pain
It is unclear whether the increased cost of
the MDCT test is associated with better
patient outcomes
8
Objective

To estimate the cost-effectiveness of MDCT
in the ED compared to the current standard
of care for the evaluation of low risk chest
pain patients presenting to the ED
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Study Design


Decision analytic model
Compare the health outcomes and costs that
result from different risk-stratification
strategies for ED patients with low risk
chest pain
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Population

54 year old male, low risk chest pain


Reflects the average age and most prevalent
gender
3 Scenarios
1) OU care followed by stress ECG testing
 2) OU care followed by stress
echocardiography
 3) No OU care, MDCT done in ED

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12
OU + Stress Echo Tree
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MDCT Tree
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Inputted Parameter
Sensitivity/Specificity
Sensitivity MDCT, %
Specificity MDCT, %
Sensitivity Stress Echocardiography, %
Specificity Stress Echocardiography, %
Sensitivity Stress ECG, %
Specificity Stress ECG, %
Probabilities
Probability of CAD, %
Probability of Missed CAD-Death, %
Probability of Missed CAD- MI, %
Probability of Missed CAD- Health, %
Probability of Death after Angio, CAD Pos, %
Probability of Death after Angio, CAD Neg, %
Probability CABG, %
Probability of Med Management, %
Probability of PCI, %
Probability of CABG and Death, %
Probability of CABG and MI, %
Probability of Med Management and Death, %
Probability of Med Management and MI, %
Probability of Death after PCI, %
Probability of MI after PCI, %
Base
Case
Analysis
Range Used in
Sensitivity
Analysis
99
84
85
70
74
69
80-100
60-100
60-90
60-90
60-90
65-90
6
7.7
44
49
0.1
0.02
10
10
80
3.0
3.3
2
2
2.5
8.5
1-70
2-75
10-75
10-75
.05-.5
.018-.02
1-50
1-50
50-99
1-10
1-10
1-5
1-5
1-10
1-50
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Inputted Parameter
Cost
MDCT, $
Stress Echocardiography, $
Stress ECG, $
Angiography, $
PCI, $
CABG, $
OU Physician and Hospital, $
Missed CAD and Death
Missed CAD and MI
Utility
Alive-Health
Alive-MI
Death
Life Expectancy
Life Expectancy after Health, yrs
Life Expectancy after MI, yrs
Base
Case
Analysis
Range Used in
Sensitivity
Analysis
1500
277
105
2278
12228
35723
1712
58745
15549
$750-$3000
$188-$750
$78-$312
$1282-$5126
$8273-$33092
$23240-$92958
$856-$3424
$29373-$117490
$7776-$31098
1
0.88
0
0.5-0.95
24.77
11.2
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Healthcare Costs


All costs were adjusted to 2007 U.S. dollars
using the Medical Care component of the
Consumer Price Index.
No discounting was necessary as costs and
cost-effectiveness were examined for a 30day period after adjustment to 2007 dollars.
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Sensitivity Analysis


Test robustness of the results to changes in
model assumptions and estimates
Threshold sensitivity analysis

To determine at which point these input
parameters resulted in a substantial impact on
cost, effectiveness, or cost-effectiveness of each
modality
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Probabilistic Sensitivity Analysis

Conducted a Monte Carlo analysis to evaluate
uncertainty by varying all of the input model
variables simultaneously to assess the overall
variability of the model


Each scenario was simulated 10,000 times using Monte
Carlo simulation
This method accounts for variability among
individuals and tests, which more closely
resembles reality. The 95% confidence intervals
of the ICERs were determined
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Results
Stress ECG Stress Echo
MDCT
Cost
$3,461
$3,265
$2,684
QALYs
24.59
24.63
24.69
ICERs
Echo vs. ECG
(95%CI)
Dominant (Dominant$123,467/QALY)
ICERs
ICERs
MDCT vs. ECG
MDCT vs. Echo
(95%CI)
(95%CI)
Dominant (Dominant- Dominant (Dominant$7,332/QALY)
$29,738/QALY)
Dominant: Less Costly, More Effective
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Sensitivity Analysis


MDCT remained dominant to the other strategies
because it had better outcomes and lower costs
Five input parameters that resulted in the MDCT
having higher costs than OU + Stress Echo





cost of MDCT > $2,097
Base case ($1500)
cost of OU care < $1,092
Base case ($1712)
prevalence of CAD > 70%
Base case (6%)
specificity MDCT < 65%
Base case (84%)
indeterminate rate MDCT > 30%
(3.8%)
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Limitations


Our analysis relies heavily on published assessments
We use sensitivity and specificity of the MDCT from
of studies with a CAD prevalence of 64%.



All input parameters taken from the literature may be overor understated in this low risk OU population
Radiation from a 64-slice scanner evaluating the
coronary arteries has a lifetime risk of cancer
Patients who have significant CAD on MDCT do need
to get another catheterization.

This requires another dye load, renal pathology is not
modeled
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Conclusions


MDCT strategy is less costly and more
effective than both OU based strategies in
chest pain patients presenting to the ED
Largely due to the diagnostic test
performance of MDCT and the avoidance of
OU costs
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