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Fig. 20.19 Curved multiplanar reconstructions of CCTA from patients representing different levels of risk based on CCTA fi ndings ( top ) and
possible subsequent management. The arrow points to an intermediate-to-high fi nding on CCTA. ICA invasive coronary angiography
Fig. 20.20 Conceptual
approach based on initial
CCTA to diagnosis and
management of coronary
artery disease in symptomatic
patients with an intermediate
pre-test likelihood of CAD.
Abnl abnormal, revasc
revascularization (Adapted
from Schuijf et al. [ 84 ] with
permission from Springer)
20 Value Based Imaging for Coronary Artery Disease: Implications for Nuclear Cardiology and Cardiac CT
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368
testing approach—unless functional testing is combined
with anatomic assessment such as performing an adjunctive
CAC scan—potentially often stopping a cycle of multiple
repeat tests. The cost- effectiveness CCTA in this patient
population has recently been reviewed [ 85 ]. At the other end
of the spectrum of likelihood of hemodynamically signifi cant disease, a reasonable hypothesis would be that if anatomic approach to assessment of CCTA alone is used—not
taking advantage of functional information that might be
derived from CCTA—CCTA might not prove to be of value
(Fig. 20.21 ). For example, if a very high CAC score is pres-
ent in a substantial proportion of patients—leading to a high
proportion of nondiagnostic studies—CCTA might be associated with an increase in downstream testing, either functional testing or invasive coronary angiography, potentially
not changing outcomes compared to a functional approach
but increasing costs. Adding “functional” information to
CCTA—such as stress CT perfusion or FFR CT might extend
the population in whom the initial CCTA approach will
likely be of value.
Stress imaging with SPECT-MPI remains by far the most
common approach to testing of the patient with an intermediate likelihood of hemodynamically signifi cant CAD. Given
the wide availability of stress imaging methods compared to
the current less widely available CCTA imaging, the predominance of the stress imaging approach is likely to remain for a
considerable amount of time (Fig. 20.22 ). With the initial
stress imaging approach, CCTA could be used as a second test
when the results of stress testing are equivocal or discordant
(e.g., severe ST depression with a normal MPI study) [ 86 ].
A drawback of stress imaging without anatomic assessment
in patients with an intermediate likelihood of CAD is that the
methods detect only patients with hemodynamically signifi cant lesions and fail to identify patients with subclinical atherosclerosis in whom aggressive medical and lifestyle
modifi cation might prevent subsequent cardiac events. While
SPECT-MPI assessment of ischemia is an excellent test of
short-term prognosis, CAC scanning may be a better test of
long-term prognosis. Over a decade ago, it was recognized that
high CAC scores are common in patients with normal SPECTMPI [ 25 ] (Fig. 20.23 ). Thus, patients with non-obstructive
CAD, previously unknown, could be afforded effective preventive therapies, such as statins and aspirin. In this regard, the
coupling of CAC scanning with SPECT- or PET-MPI discussed above could provide an effective alternative to the
CCTA as a fi rst choice approach to management of the patient
with suspected SIHD. It has further been suggested [ 87 ] that a
powerful, inexpensive alternative that may prove to be of value
Fig. 20.21 Hypothesized value of using CCTA in symptomatic
patients with suspected stable ischemic heart disease ( SIHD )
Fig. 20.22 MPI approach to
diagnosis and management of
CAD in symptomatic patients
with an intermediate-to-high
pre-test likelihood of CAD or
known CAD (*Indicates that
there may be benefi t from
CAC scanning to assess
underlying subclinical
atherosclerosis). Int
intermediate, ICA invasive
coronary angiography, CCS
coronary calcium scan)
(Adapted from Schuijf et al.
[ 84 ] with permission from
Springer)
D.S. Berman et al.
https://t.me/medicina_free
369
is the combination of an ECG stress test without imaging with
a CAC scan—the “coronary calcium treadmill test.”
Patients with a High Likelihood of CAD
or Known CAD
In contrast to patients with an intermediate likelihood of
CAD, patients with a high likelihood of CAD are generally
considered by their clinicians to have CAD and are treated
accordingly. If limiting symptoms are present, the patient is
usually directly sent for invasive angiography. In patients
without limiting symptoms, stress imaging is performed to
assess the extent and severity of ischemia in order to guide
the decision for revascularization. An extensive body of
information has demonstrated the prognostic power of ischemia testing with SPECT- or PET-MPI as well as with stress
echocardiography and stress cardiac magnetic resonance
imaging [ 88 – 91 ]. For SPECT and PET, risk has been shown
to increase as a function of stress perfusion abnormality in
virtually all subsets of patients with known or suspected
CAD [ 89 , 92 ]. Importantly, as noted above, these include the
categories of patients in whom CCTA is contraindicated or
likely to be non-diagnostic.
Large randomized clinical trials have suggested that anatomic assessment of disease alone does not provide evidence
of revascularization benefi t in most patients [ 93 ]. Most fre-
quently quoted in this regard are the results of the COURAGE
trial [ 94 ] and the BARI 2D trial [ 95 ] which did not demon-
strate benefi t over optimal medical therapy as an initial
strategy.
There is evidence, however, that an ischemia guided
approach to revascularization can be of benefi t. Noteworthy
in this regard are the results of the FAME studies. The FAME
trial provided evidence that a revascularization strategy
based on the use of ischemia testing as assessed by invasive
FFR—with a cut-off of ≤0.80 considered as the criterion to
perform PCI—resulted in improved outcomes in patients
with multivessel CAD compared to a strategy based on anatomic assessment alone [ 96 , 97 ]. Patients with FFR guided
revascularization had a lower event rate (death, non- fatal MI,
repeat revascularization) than the group in the angiographically guided strategy. Subsequently, the FAME II trial randomized stable patients with FFR ≤0.80 to PCI vs medical
management [ 98 ]. The trial was stopped before reaching its
target sample size due to excessive events—death, non-fatal
MI, and unstable angina—in the medical therapy arm. While
there were no differences between the FFR guided and the
medical management approaches with respect to hard events
alone, the results demonstrated an outcome benefi t of ischemia driven decisions for revascularization using the composite endpoint (p <0.001). The ability of an FFR-guided
approach to reduce cardiac events was also demonstrated in
a large registry of 7358 patients with stable disease studied at
the Mayo Clinic [ 99 ].
Registry data with SPECT-MPI has provided evidence
that supports the approach of ischemia driven revascularization. The potential that the amount of ischemia on SPECTMPI to predict benefi t with revascularization was fi rst
described in a single center registry by Hachamovitch et al.
in 1998 [ 100 ]. Subsequently, this benefi t was documented in
a larger population of 10,627 patients without prior CAD
who underwent SPECT MPI. A “proof-of- principle” question was asked: can imaging identify appropriate and benefi cial treatment strategies and at what threshold of abnormality
does therapeutic effi cacy shift [ 101 ]. After adjusting for dif-
ferences between medically treated and revascularized
patients—including a propensity score adjustment to correct
for differences in referral patterns to treatment options—
patients with extensive myocardial ischemia by SPECT MPI
exhibited a survival benefi t with myocardial revascularization for the intermediate-term occurrences of cardiac death
(Fig. 20.24 ). By contrast, among those with no myocardial
ischemia, the cardiac death rate was higher with myocardial
Fig. 20.23 Distribution of
coronary artery calcium ( CAC )
scores for 1119 patients
manifesting a normal myocardial
perfusion single-photon emission
computed tomography ( MPS )
( left ) and the 76 patients with an
ischemic MPS ( right ) (Adapted
from Berman et al. [ 25 ] with
permission from Elsevier)
20 Value Based Imaging for Coronary Artery Disease: Implications for Nuclear Cardiology and Cardiac CT
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370
revascularization than with medical therapy. The “cross-over
point” at which myocardial ischemia tipped the balance
towards myocardial revascularization appeared to be more
than 10 % ischemic myocardium. Thus, this study provided
insight into a potential linkage between cardiac imaging
results, patient treatment, and patient clinical outcomes. This
linkage was further examined in higher-risk patient subsets
including those with prior revascularization or small prior
MI [ 102 ], elderly [ 103 ], and high risk diabetic patients by a
recent study [ 104 ]. In long-term follow-up of 5200 elderly
patients (≥75 years old) undergoing MPI, over 25 % of
whom had prior MI, the threshold for benefi t from revascularization appeared 15 % myocardium ischemic [ 103 ]. In
another long- term follow-up study of 13,969 patients from
the same registry, those with moderately to severely extensive ischemia appeared to benefi t from revascularization
even in the presence of known CAD or prior revascularization, providing they did not have extensive prior MI (>10 %
fi xed defect by MPI) [ 102 ]. The threshold for this apparent
benefi t was between 10 and 15 % myocardium ischemic
(Fig. 20.25 ).
A small but provocative study has suggested that addition
of quantitative myocardial blood fl ow reserve measurements
may be associated with cardiac events independently and
may modify prediction of benefi t from early revascularization. In a study of 329 patients referred for invasive coronary
angiography after PET scanning with CFR measurements,
Taqueti et al. evaluated the relationship between CFR and
observed benefi t from revascularization. Patients were studied for the interaction between CFR fi ndings and whether or
not the patients were revascularized with respect to cardio-
vascular death or heart failure over a follow up of 3.1 years.
Overall, only patients with reduced CFR had a signifi cant
improvement with revascularization. Further, a signifi cant
interaction between CFR and early CABG was noted, but not
with PCI, such that patients with reduced CFR who underwent CABG had much greater freedom from event rate than
patients those with low CFR who underwent PCI (Fig. 20.26 )
[ 105 ]. Gould et al. have recently expanded on the concepts
suggested by the results of this small study [ 106 ], noting the
importance of diffuse CAD in increasing the risk of myocardial infarction and decreasing the likelihood that stent placement across individual lesions will prevent MI. They further
note that diffuse CAD can be assessed with CFR measurements by PET but are not assessed by FFR and conclude that
consideration of CFR might improve selection of patients for
revascularization.
While registry data suggests a benefi t of revascularization
in patients with moderate to severe ischemia, this benefi t has
not yet been validated in a randomized controlled trial.
Whether an ischemia guided approach in SIHD improves
outcomes is currently being evaluated in the ISCHEMIA
trial (the International Study of Comparative Health
Effectiveness with Medical and Invasive Approaches). This
study is randomizing patients with moderate-to-severe
ischemia based on the 10 % ischemia criterion suggested
from the Cedars-Sinai data—as the entry criterion. Patients
with left main CAD—assessed by blinded CCTA—are
excluded. The remaining patients are being randomized to an
invasive approach of catheterization with intent for ischemia
guided revascularization + optimal medical therapy (OMT)
vs a no catheterization approach with OMT alone.
Fig. 20.24 Relationship
between %myocardium
ischemic and log of the
hazard ratio in 10,647
patients treated either with
medical therapy ( dashed line )
or early revascularization
(<60 days post-SPECT MPS;
solid line ) based on
multivariable modeling. In
the setting of little or no
ischemia, medical therapy is
associated with superior
survival; with increasing
amounts of ischemia a
progressive survival benefi t
with revascularization over
medical therapy is present.
95 % confi dence intervals are
shown by the closely dotted
lines (*Indicates p <0.001.)
(Adapted from Hachamovitch
et al. [
101 ] with permission
from Wolters Kluwer Health,
Inc)
D.S. Berman et al.
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371
Value of Ischemia Testing in the Patient
with a High Likelihood of or Known CAD
A reasonable hypothesis is that the value of ischemia testing
will depend on the pre-test risk (Fig. 20.27 ). If the ischemia
guided management approach is confi rmed in randomized
clinical trials, there will be an opportunity for the value of
ischemia testing to be shown; however, this value would
likely be strongly dependent on the pre-test risk. If the pretest risk is suffi ciently high, ischemia testing might lead to
improved outcomes by appropriately guided revascularization. Costs might be decreased compared to an approach
without ischemia testing—such as that of using coronary
CTA to guide the decision for proceeding to catheterization
in this high risk group—since the use of CCTA alone might
be associated with an excessive number of catheterizations
and revascularizations as discussed above. As noted above,
the use of CT perfusion of FFRCT measurement in conjunction with CCTA might provide a means by which CCTA as
the initial test could be of value in this patient group.
If used in a population of low risk, however, the ischemia
testing is likely not to be of value. In this regard, there is an
indication that the risk of patients currently undergoing testing may be too low for the testing to be of value. In a study
of 39,515 patients referred for SPECT-MPI to the Cedars-
Sinai laboratories, Rozanski et al. have shown that there has
been a dramatic reduction in the frequency of abnormal test
results over time [ 107 ]. Whereas in 1991 approximately
40 % of patients referred for testing had ischemia by SPECTMPI, by 2009 this rate was less than 10 % (Fig. 20.28 ).
Similar fi ndings have now been reported from other centers.
What could be the explanation of the very low observed
prevalence of abnormal SPECT-MPI studies? One answer
is that the widely used Diamond-Forrester criteria for
determining pre-test likelihood of angiographically signifi cant CAD may not be applicable in the types of patients currently being referred for noninvasive testing. Data from the
CONFIRM registry are enlightening in this regard. Cheng
et al. reported that the Diamond-Forrester criteria markedly
overestimated pretest likelihood of CAD [ 108 ]. In 8106
patients in with nonanginal chest pain, atypical angina, or
typical angina, the Diamond-Forrester pre-test likelihood of
angiographically signifi cant CAD was 51 %. However, the
observed frequency of ≥50 % stenosis was 18 %. Based on
the pooled data from CCTA studies, approximately 90 % of
patients with CCTA stenosis have ICA stenosis. Based on the
report by Tonino et al. from the FAME trial, only 57 % of
lesions judged visually to have ≥50 % stenosis have ischemia by FFR [ 109 ]. Further, it a meta-analysis by Zhou et al.,
Hazard ratio
(Early revascularization vs. medical therapy)
Hazard ratio
(Early revascularization vs. medical therapy)
Hazard ratio
(Early revascularization vs. medical therapy)
Hazard ratio
(Early revascularization vs. medical therapy)
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0.00
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0.00
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0.00
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0.00
0510
%myocardium ischaemic
15 20 25
0510
%myocardium ischaemic
n = 13,969; FU 8.7±3.3 yrs
15 20 25
0510
%myocardium ischaemic
15 20 25
0510
%myocardium ischaemic
15 20 25
n = 8,791 n = 1,542
n = 11,880
n = 3,216
<10% fixed defect
Prior MI
No Known CAD Prior Revasc
1.51
1.29
1.10
0.93
0.80
0.68
1.49
1.28
0.92
0.89
0.87
0.85
0.80 0.80
1.10
0.95
0.80
0.70
1.07
1.18
0.98
0.89
0.80
0.74
ab
cd
Ischemia and Scar and Therapeutic Benefit
Fig. 20.25 Hazard ratio
associated with early
revascularization compared
with medical therapy at
specifi c values of
%myocardium ischemic.
( a ) patients with no prior
coronary artery disease,
( b ) patients with prior
revascularization but no prior
myocardial infarction,
( c ) patients with prior MI,
and ( d ) patients with <10 %
fi xed defect. P- values as per
Cox proportional hazards
model (Adapted from
Hachamovitch et al. [ 102 ]
with permission from Oxford
University Press)
20 Value Based Imaging for Coronary Artery Disease: Implications for Nuclear Cardiology and Cardiac CT
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it has been shown that only 77 % of patients with ischemia
by FFR have ischemia by SPECT-MPI [ 110 ]. Multiplying
these rates together, the result is that if the patients sent for
testing have an intermediate pre-test likelihood of CAD by
Diamond-Forrester criteria, it would be expected that 8.6 %
would have ischemia by SPECT—very similar to what was
reported by Rozanski et al. [ 107 ]. The results of the
PROMISE trial confi rm these calculations. While the pretest
likelihood of CAD using the Diamond-Forrester criteria was
53.3 %, only 11.7 % had stenosis by CCTA and only 10.7 %
had abnormal functional studies [ 83 ].
An updated approach to assessment of the pretest likelihood of CAD as well as of risk—the “CONFIRM Risk
Score” in patients referred to noninvasive testing has recently
been described based on an analysis of the CONFIRM data
[ 111 ] with validation in the Cedars-Sinai nuclear cardiology
database. The simple to implement score is illustrated in
Fig. 20.29 . An intuitive number is assigned for age (e.g., 4
for 40–49 years, 7 for >70 years), and 1 or 0 are assigned
based on sex, angina, diabetes, hypertension, family history
of premature CAD, and smoking. With a simple table the
number converts to a risk of death or MI or a pre-test likelihood of CAD. The CONFIRM risk score was better calibrated than the Framingham Risk Score or the
Diamond- Forrester pre-test likelihood calculations. Use of
the CONFIRM risk score could lead to a more effective decision as to whether to use an imaging test in a given patient
and which test to choose, and, ultimately, to a greater opportunity of noninvasive testing to demonstrate value.
CFR + or – vs Revasc + or – CFR + or – vs Type of Revasc
Adjusted
‡
Adjusted
‡
100
90
80
CFR low, revasc –
CFR low, PCI
CFR low, CABG
CFR low, revasc +
N = 329
n = 193
p = 0.61
p = 0.01
p = 0.002
Freedom from Event
§
(%)
Freedom from Event
¶
(%)
70
60
50
100
90
80
70
60
50
CFR high, Revasc (+)
CFR high, Revasc (–)
CFR low, Revasc (+)
CFR low, Revasc (–)
CFR high, CABG
CFR high, PCI
CFR low, CABG
CFR low, PCI
0 200 400 600
Days
800 1000
1200
0 200 400 600
Days
800 1000
1200
CFR is Associated with Cardiac Events Independently of Stenosis and
Modifies the Effect of Early Revascularization
Fig. 20.26 Freedom from events according to coronary fl ow reserve
( CFR ) and early revascularization ( Revasc ) ( left ) and type of revascu-
larization (revasc) right. Freedom from cardiovascular death or heart
failure admission differed signifi cantly among subgroups stratifi ed by
CFR and revascularization ( left ) (overall log-rank P = 0.03; adjusted
P = 0.002) Patients with high CFR, independently of revascularization,
experienced lower rates of events, whereas those with low CFR who did
not undergo revascularization experienced the highest rate of events. In
the subgroup of patients who underwent revascularization ( right ), there
was no difference in event-free survival among those with high CFR
(log-rank P = 0.76; adjusted P = 0.61), but in those with low CFR, only
those who also underwent coronary artery bypass grafting (CABG), vs
percutaneous coronary intervention ( PCI ), experienced lower rates of
events (log-rank P = 0.02; adjusted P = 0.01) (Adapted from Taqueti
et al. [ 105 ] with permission from Wolters Kluwer Health, Inc)
Fig. 20.27 Hypothesized value of using SPECT- or PET-MPI (ischemia testing) in symptomatic patients with suspected stable ischemic
heart disease (SIHD)
D.S. Berman et al.
https://t.me/medicina_free
373
Assessment of Patients with Heart Failure
and Known or Suspected CAD
At the end of the spectrum of patients with CAD who are
referred for testing are the patients with heart failure. In this
population, CCTA has a limited role—predominantly being
to rule out ischemic cardiomyopathy in patients presenting
with heart failure of unknown cause and in whom the likelihood if CAD is considered to be relatively low [ 112 ].
In the patient with an ischemic cardiomyopathy, myocardial
viability imaging (PET or CMR) would be more likely than
CCTA to be of value in guiding the decision for revascularization or transplantation.
Value of Imaging Depends on the Effect
of Imaging on Patient Management
The fundamental value equation is quality divided by cost.
Test quality ultimately rests in benefi cial patient outcomes.
Costs relate not only to the cost of testing but also to all of the
costs resulting from the test. In consideration of the value of
noninvasive imaging, there can be no value if the test does not
improve the relationship between outcomes and costs, and
this is dependent on the manner in which test results change
patient management. The test itself has no effect. Unfortunately,
there is evidence that often this last link-the link between the
test and treatment change-is not as strong as it needs to be.
The SPARC (Study of Myocardial Perfusion and Coronary
Anatomy Imaging Roles in Coronary Artery Disease)
addressed these issues by evaluating 90-day post-test rates of
catheterization and medication changes in a prospective registry of 1703 patients without a documented history of coro-
nary artery disease and an intermediate to high likelihood of
CAD undergoing cardiac SPECT- or PET-MPI or CCTA
[ 113 ]. These results were classifi ed as normal (or non-
obstructive for CCTA), mildly abnormal, and moderately or
severely abnormal. Baseline medication use was relatively
infrequent. At 90 days, 9.6 % of patients underwent catheterization. While the rates of catheterization and medication
changes increased in proportion to test abnormality fi ndings,
among patients with the most severe test result fi ndings,
38–61 % were not referred to catheterization, 20–30 % were
not receiving aspirin, and 20–25 % were not receiving a lipidlowering agent at 90 days after the index test. Risk-adjusted
analyses revealed that changes in use of aspirin and lipid lowering agent were greater after CCTA. The authors concluded
that overall, noninvasive testing had only a modest impact on
clinical management of patients referred for clinical testing.
Although post-imaging use of cardiac catheterization and
medical therapy increased in proportion to the degree of
abnormality fi ndings, the frequency of catheterization and
medication change suggests possible under-treatment of
higher risk patients. Even in the severely abnormal group,
only 27 % had no catheterization or medication change.
As noted above, in the Scot-Heart trial, changes in treatment after CCTA testing compared to the non-imaging arm
were clear, with 18 vs 4 % of patients being placed on preventive therapy in the CCTA and control arms, respectively. As
noted, there was also a trend toward improved hard outcomes
in the CCTA arm of the study. The effects of the CCTA vs
functional testing in the PROMISE trial regarding changes in
therapy have not yet been reported. The results of the
FACTOR-64 study provide promising results regarding the
Fig. 20.28 Year by year
prevalence of abnormal and
ischemic SPECT-MPI studies
between 1991 and 2009
among 39,515 diagnostic
patients tested at Cedars-Sinai
Medical Center (Adapted
from Rozanskiet al. [ 107 ]
with permission from
Elsevier)
20 Value Based Imaging for Coronary Artery Disease: Implications for Nuclear Cardiology and Cardiac CT
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infl uence of test results on patient therapy and possibly on hard
outcomes; however, it should be noted, that changes in therapy
in this study based on test results were part of the study design.
The principal manner in which SPECT-MPI or PET-MPI studies alter patient management is principally in guiding decisions to consider revascularization. Regarding institution of
preventive management measures after testing, the combined
use of CAC with SPECT- or PET-MPI could allow similar
effects as observed with CCTA with the use of MPI. Whether
the ability of PET-MPI to assess myocardial blood fl ow
reserve, with its prognostic implications, and potential added
information regarding benefi t from revascularization, will
affect changes in patient management has yet to be examined.
The ability of a test to affect outcomes is dependent on
and degree to which the test to the manner in which test
results change therapy. The steps involved in this potential of
testing to affect outcomes are well exemplifi ed by the
PARR-2 study (Fig. 20.30 ), which involved FDG PET scan-
ning [ 114 ]. In this study, 430 patients in 9 centers with heart
failure, known or suspected CAD and LVEF ≤35 % were
randomized to a management plan assisted by FDG PET
(n = 218) or standard care (n = 212), with specifi c recommendations regarding the use of FDG PET information for revascularization decisions. The outcome was a composite of
cardiac death, myocardial infarction, and recurrent hospital
stay for cardiac cause within 1 year. In the overall trial, there
was no signifi cant difference in the hazard ratio for the composite outcome in the PET vs SOC arm (p = 0.15). For
patients in whom the PET recommendations were followed,
the hazard ratio was signifi cant (p = 0.019), illustrating that a
test results can have a benefi cial effect on outcome only if the
test appropriately changes therapy. The further reliance of
the outcome benefi t of testing was subsequently illustrated in
this study when expertise in performance and clinical use of
the testing is present. A post-hoc analysis was performed
comparing a subgroup of patients studied in fi ve hospitals
Fig. 20.29 Table illustrating the CONFIRM risk score. Illustrated is
scoring for a 65 year old male with a history of hypertension and smoking. The CONFIRM risk score (*) is 9, which would predict an 8.02 risk
of death or MI and a 31 % likelihood of CAD (≥ 50% stenosis)
(Reprinted from Min et al. [ 111 ] with permission from Elsevier)
D.S. Berman et al.
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375
with greater experience in and access to the use of the PET
assisted strategy in the PARR-2 trial [ 115 ]. There was a sig-
nifi cant reduction in cardiac events in the patient population
studied at the fi ve sites with expertise (p = 0.005) that had not
been seen in the overall trial.
Conclusion
Technology cardiac CT and nuclear cardiology is con-
stantly improving, such that the information provided be
each form of testing is expanded, potentially decreasing the
need for layered testing. The value of cardiac imaging
depends on impact on outcomes and all costs related to per-
formance of a test. In clinical applications, the potential
value of the modalities is related to the setting in which
they are employed. For prevention, data is strong in that
CAC scanning can provide value by improving outcomes.
In the patient with acute chest pain, CCTA appears to be
able to shorten time in the hospital and reduce costs. In
patients with suspected SIHD and an intermediate pre-test
likelihood of CAD, the use of CCTA appears to be valuable. In patients who have known CAD or in whom a nondiagnostic CCTA is likely, improvement in outcomes is
less likely and testing for ischemia may be preferred. In
patients with a very high likelihood of CAD or known
CAD, registry data suggests that ischemia testing, such as
that provided by SPECT- or PET-MPI studies, may improve
outcomes by improving selection of patients for revascularization. The ISCHEMIA trial will test whether a strategy
basing decisions for revascularization on noninvasive
assessment of ischemia is improves outcomes. In patients
with heart failure, the use of CCTA is primarily to rule out
ischemic cardiomyopathy. As with any form of testing,
assessing the pre-test likelihood of disease is of paramount
importance in determining the need for a test which could
be of value. Recent data show that the pretest likelihood of
Influence of Adherence to Strategies and Expertise on Impact of
FDG-PET on Patient Outcomes: Results of the PARR-2 Study
1.00.80.60.40.20.0
Overall
Adhering to strategy
P=0.15 P=0.019
Standard arm
PET arm
Standard arm
ADHERE arm
0 100 200
Days Days
300 100 200 300
0.8
0.6
0.4
0.2
0.0
0 50 100 150 200 250
PET
Standard
More experienced center
P=0.005
Days
300 350 400
Cardiac event free survival probability
Fig. 20.30 Infl uence of adherence to strategies and expertise on impact
of FDG-PET on patient outcomes as shown in two publications from the
PARR-2 Trial. The top two illustrations illustrate composite outcome of
cardiac death, myocardial infarction, recurrent hospital stay for cardiac
cause within 1 year. Green PET arm, Orange Standard arm. In the over-
all trial ( left ), no survival benefi t was shown. In the subset in whom the
planned therapeutic strategy of the trial based on PET viability results
was followed ( right ), a signifi cant survival benefi t in the PET arm was
seen. When patients who were tested in a center with greater experience
with FDG-PET were assessed ( lower illustration), an even greater sur-
vival benefi t in the PET arm was shown ( Top two panels : (Adapted from
Beanlands et al. [ 114 ] with permission from Elsevier))
20 Value Based Imaging for Coronary Artery Disease: Implications for Nuclear Cardiology and Cardiac CT
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376
CAD and pretest risk is markedly overestimated by traditional approaches, most likely explaining a marked increase
in frequency of normal stress SPECT-MPI studies. Updated
methods for assessment of pre-test risk may lead to
improved utilization of cardiac imaging procedures. In
selected heart failure patients, of myocardial viability using
PET or MRI may prove to provide value. In all of the applications of noninvasive imaging, value can only be achieved
if the appropriate patients are selected for testing and if the
test result changes therapy, such that cost savings or
improved outcomes can follow the testing strategy.
Acknowledgement Supported in part by the Adelson Family
Foundation and the Diane and Guilford Glazer Foundation
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