1. Cardiac Imaging • Original Research
Kelly et al.
CTA in Patients Without Coronary Calcification
Cardiac Imaging
Original Research
Coronary CT Angiography
Findings in Patients Without
Coronary Calcification
Jason L. Kelly 1
David Thickman2
Simeon D. Abramson1
Pei R. Chen1
Stanley F. Smazal1
Matthew J. Fleishman1
Sharmila C. Lingam1
Kelly JL, Thickman D, Abramson SD, et al.
Keywords: Agatston method, atherosclerosis, calcium
scoring, coronary artery disease, coronary calcifications, coronary CT angiography
DOI:10.2214/AJR.07.2954
Received July 29, 2007; accepted after revision
January 28, 2008.
1
Thoracoabdominal Imaging, Radiology Imaging
Associates, 10700 E Geddes Ave., Ste. 200, Englewood,
CO 80210. Address correspondence to J. L. Kelly
(jason.kelly@riaco.com).
2
Nighthawk Radiology Services, Coeur d’Alene, ID.
AJR 2008; 191:50–55
0361–803X/08/1911–50
© American Roentgen Ray Society
50
objective. Coronary calcification detected by CT is a marker for atherosclerotic disease with prognostic significance. However, potentially unstable plaque is characterized by a
high lipid content rather than calcification, which may make detection using the calcium
score difficult. To assess the prevalence and severity of atherosclerotic disease in patients
without coronary calcification, we evaluated findings in patients with a normal calcium score
undergoing coronary CT angiography (CTA).
materials and METHODS. Data from 794 consecutive coronary CTA examinations performed between February 2005 and May 2007 were reviewed. The calcium scores
were determined as part of coronary CTA examinations, and calcium was quantified according to the Agatston method. Patients underwent coronary CTA because of high risk for coronary artery disease (53%) or atypical symptoms or abnormal stress test results (47%). On
coronary CTA, plaque was characterized as mild disease without hemodynamically significant
stenosis, moderate disease without hemodynamically significant stenosis, moderate stenosis
(50–70% luminal narrowing), or severe stenosis (> 70% luminal narrowing).
RESULTS. Of the 729 patients included in the study, 325 (45%) had a normal calcium
score. Of these, 167 (51%) had noncalcified plaque on coronary CTA. Twelve (3.7%) of those
with a normal calcium score had at least moderate stenosis, five (1.5%) of whom had severe
stenosis. Eight of the 12 patients with significant stenosis underwent invasive angiography and
coronary stenting.
CONCLUSION. A considerable atheroma burden including significant stenoses may be
present in patients with no coronary calcification. Although the calcium score does add prognostic value to standard risk factors and serum markers, imaging the vessel wall directly may
be helpful to identify noncalcified plaque and guide therapy.
T
he presence of calcium in the coronary arteries has been shown to
be a marker for atherosclerotic
disease [1, 2]. This calcium is detectable on CT and is quantifiable using the
Agatston method [3, 4], which adds prognostic
information to available demographic and serologic risk stratification [5, 6]. However, CT
performed for calcium scoring is not able to
show noncalcified atheroma or stenosis. These
findings are inferred from the presence of calcified plaque using probabilistic models [7].
Invasive angiographic studies have been performed to evaluate the significance of disease
in patients with normal calcium scores. Those
studies have shown a high negative predictive
value for calcium scoring: 80% for any disease
and up to 100% for significant stenosis [8, 9].
However, angiography alone has also been
shown to significantly underestimate plaque in
anatomic studies [10], particularly in vessels
with compensatory positive remodeling.
Coronary CT angiography (CTA) is an
emerging noninvasive technique that can
evaluate both calcified plaque and noncalcified plaque. Coronary CTA is able to show
the lumen of the coronary arteries as well as
the vessel wall, analogous to intravascular
sonography [11–13]. Multiple studies have
shown coronary CTA to have a high negative
predictive value for the detection of coronary
atherosclerosis: greater than 95% for significant
stenosis [14, 15] and approximately 90% for
any plaque [11, 12]. Because coronary CTA
uses IV contrast material, it is able to detect lowvolume, noncalcified plaque that is not visible
on CT performed for calcium scoring (Fig. 1).
Identification of small-volume soft plaque
is the crux of coronary artery disease management. Investigators have repeatedly shown
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2. CTA in Patients Without Coronary Calcification
A
B
Fig. 1—52-year-old man with increased fatique on long-distance runs.
A, Coronary CT angiography image shows large soft plaque (between arrows) that is causing severe stenosis in the left main coronary artery.
B, Corresponding coronary angiogram shows severe stenosis of the left main artery (arrow). The patient went on to have a stent placed.
that acute coronary syndromes most frequently result from the rupture of these small
plaques, which are generally not flow-limiting, do not cause stenosis, and may not be
calcified [16]. Calcification is generally a
marker of plaque stability, whereas unstable
plaque is characterized by a large lipid core,
thin fibrous cap, and inflammation. This unstable plaque has been termed the “vulnerable plaque” and is the target of current treatment algorithms.
Although CT performed for calcium scoring is able to detect calcified atheromatous
disease, patients with only noncalcified
plaque are a potential diagnostic weakness.
The detection of noncalcified plaques and
stenoses has potential importance because it
encourages therapeutic management to be
initiated in the earliest stages of plaque formation and identifies previously occult disease in a group of patients at high risk for
plaque rupture. To assess the presence of atherosclerosis in patients with normal calcium
scores, we reviewed our findings in patients
undergoing CT for calcium scoring as part of
a coronary CTA examination.
Materials and Methods
A total of 794 consecutive coronary CTA
examinations in 794 patients were performed
from February 2005 to May 2007 at three sites.
Calcium scores were not obtained in patients with
coronary stents or bypass grafts, and those patients
were excluded. In the remaining 729 examinations,
a CT scan was obtained for calcium scoring
immediately before CTA.
The mean age of the patients in our study was 56
years (range, 17–77 years), and 32% were female.
AJR:191, July 2008
TABLE 1: Inclusion Criteria for Coronary CT Angiography
Criteria
Atypical chest pain
Abnormal or indeterminant exercise stress test
No. (%) of Patients (n = 729)
204 (28)
36 (5)
Abnormal or indeterminant nuclear stress test
102 (14)
Age ≥ 45 y
649 (89)
Family history of heart disease
370 (51)
Hyperlipidemia
191 (26)
Hypertension
187 (26)
Diabetes
48 (7)
Smoking (current smoker or history of smoking)
61 (8)
Patient ethnicity was not recorded, although most
patients were white. For each study, the calcium
score, presence and type of plaque, and study quality
were recorded. Follow-up data, including invasive
angiography, intravascular sono­ raphy, and stress
g
test results, were collected as well. This retrospective
study met the standards of our hospital’s review
board and was exempted from review.
Patients were referred for atypical symptoms
(28%), abnormal or indeterminant findings on
exercise stress test (5%), abnormal or in­ eter­
d
minant findings on nuclear stress test (14%), or
coronary artery disease assessment in asympto­
matic patients with risk factors (53%) (Table 1).
The scanning criteria for asymptomatic patients
included the following: age of 45 years or more;
family history of heart disease, hyperlipidemia,
hypertension, or diabetes; or smoking (current or
previous). Any patient with abnormal or indeter­
minant findings on a stress test, either exercise or
nuclear, was considered to be symptomatic. For all
patients less than 45 years old, coronary CTA was
performed as part of the evaluation for atypical
chest pain or abnormal findings on a stress test.
Coronary CTA was not performed for evaluation
of suspected acute coronary syndrome.
When a patient arrived at the radiology
department, a set of vital signs was taken and
oral metoprolol or verapamil was administered
according to the patient’s resting heart rate with a
goal of less than 60 beats per minute (bpm) during
scanning. Blood pressure, heart rate, and pulse
oximetry were monitored. After 1 hour, a second
dose of oral metoprolol was given if necessary and
tolerated. A maximum of 200 mg of metoprolol
was administered. In the case of contraindication
to β-blockade, 240 mg of oral verapamil was
given. Oxygen (2 L/min) was administered via
nasal cannula. In the absence of a contraindic­
ation, 0.4 mg of sublingual nitro­ lycerin spray
g
(Nitrolingual Pumpspray, Sciele Pharma) was
administered before the timing bolus.
Imaging was performed on a 64-MDCT scan­
ner (Somatom Sensation 64, Siemens Medical
51

3. Kelly et al.
Solutions; or LightSpeed VCT, GE Healthcare).
Before coronary CTA was per­ ormed, patients
f
underwent an unenhanced prospectively gated
study for measurement of coronary artery calci­
fication. All coronary CTA studies were perform­
ed with a total of 100 mL of IV contrast material,
either iopamidol (Isovue 370, Bracco) or iohexol
(Omnipaque 350, GE Healthcare), ad­ inistered
m
through an ante­ ubital vein at 5–6 mL/s. Scanning
c
was performed with retrospective gating and a
slice thickness of 0.6 mm. Dose modulation
techniques were used when the breath-hold heart
rate during the test bolus showed variability of
less than 5 bpm.
Images were interpreted by at least one of seven
radiologists on a 3D workstation (Vitrea, Vital
Images; or CardIQ Pro, GE Healthcare) using
axial and multiplanar reformatted data. Inter­
observer variability was not evaluated, although
most cases were double-read to promote con­
sistency of interpretations. Three readers were
involved in the interpretation of 98% (778 of 794)
of the studies.
Calcium scoring was performed according to
the Agatston method [3] before evaluation of
coronary CTA. All vessels with a luminal diam­
eter of greater than 2 mm were evaluated on
coronary CTA, including the left main (LM)
artery, left anterior descending (LAD) artery,
diagonal branches, circumflex artery (Cx), obtuse
marginal branches, right coronary artery (RCA),
acute marginal branches, posterior descending
artery, and post­ rior lateral segmental branches.
e
Plaque was characterized in one of four cate­
gories: mild disease without hemodynamically
significant stenosis, moderate disease without hemo­
d
­ ynamically significant stenosis, moderate sten­ sis
o
(50–70% diameter reduction), or severe stenosis
(> 70% diameter reduction). Hemo­ ynam­cally
d
i
significant stenosis was defined as ≥ 50% diameter
reduction. Mild disease was de­ ned as plaques
fi
resulting in a diameter reduction of less than 20%
and involving only short segments (< 2 cm) of one
or two coronary arteries. Moderate disease without
stenosis included lesions causing diameter reduc­
tion of 20–50%, involved segments of at least
moderate length (≥ 2 cm), or involved three vessels
(or a combination of these findings). The degree of
stenosis was measured using the narrowest dim­
ension of the lumen at the level of stenosis
compared with a more normal lumen diameter
distally. In patients with a technically limited
coronary CTA examination and a normal calcium
score, vessel segments that could not be evaluated
were assumed to be normal.
The p values were calculated using the twotailed Fisher’s exact test or unpaired Student’s
t test.
52
TABLE 2: Demographic Data in Patients with a Normal Calcium Score
Coronary CT Angiography Finding (No. [%] of Patients)
Characteristic
Normal
Patients
Female
Mean age (y)
Symptoms present
Noncalcified Plaque
158 (49)
82 (52)
66 (40)
49
53
65 (41)
p
167 (51)
78 (47)
0.008
< 0.001
0.32
TABLE 3: Plaque Distribution in Patients with a Normal Calcium Score
Coronary CT Angiography Finding
No. of Patients
Normal
158
Mild disease
147
Moderate disease, no hemodynamically significant stenosis
8
Moderate stenosis (50–70% luminal narrowing)
7
Severe stenosis (> 70% luminal narrowing)
5
Results
A total of 325 patients (45%) had a normal
calcium score. All 404 patients with an abnormal calcium score had detectable plaque
on coronary CTA. Overall, 21.7% (158 of
729) had normal findings, 22.9% (167 of 729)
had only noncalcified plaque, and 55.4%
(404 of 729) had calcified plaque. Hemodynamically significant stenosis was seen in
149 of 729 patients (20%).
Patients with both a normal calcium score
and negative coronary CTA findings (Table 2)
had a mean age of 49 years, significantly less
than the mean age of 53 years for those with
positive coronary CTA findings (p < 0.001).
Plaque was seen in 66 of 148 women (45%)
with a normal calcium score, which is significantly less (p = 0.026) than the 101 of 177 men
(57%) with a normal calcium score.
In 167 patients with only soft plaque, mild
disease was present in 147 (88%), and moderate disease without stenosis was present in
eight (4.8%). Twelve (7.2%) had at least
moderate (≥ 50%) stenosis, and five (3%)
had severe stenosis (> 70%) (Table 3). The
average age of patients with a normal calcium score and significant stenosis was 54
years. Six of 148 women (4.1%) showed a
significant stenosis without coronary calcium, as did six of 177 men (3.4%); this difference was not significant (p = 0.78). Eight of
the 12 had no chest pain, although three of
the asymptomatic patients had abnormal
findings on either a nuclear stress test or a
treadmill stress test.
Eight of the 12 patients with significant
stenosis underwent catheterization, including
five of six patients with an abnormal stress test
and all patients with severe stenosis. One patient with abnormal findings on a stress test in
the vascular distribution of a moderate stenosis refused to undergo angiography.
Catheter angiography images and reports
were reviewed, and coronary CTA findings
were confirmed in all patients with significant
stenosis. Stenosis measurements on coronary
CTA were within 5% of the angiographic
measurements, and there was complete agreement between coronary CTA and catheter angiography as to categorization of stenoses as
moderate or severe. The physician performing
catheter angiography was aware of the coronary CTA results. In all eight patients who
underwent catheterization, a stent was placed.
No patient with a normal calcium score and
a < 50% lesion on coronary CTA underwent
catheter angiography to our knowledge.
Symptoms did not correlate with the presence of disease or significant stenosis. Coronary CTA showed plaque in 571 patients, 278
(49%) of whom were symptomatic. Of 158
patients with a normal calcium score and normal coronary CTA, 65 (41%) presented with
symptoms. This difference was not statistically significant (p = 0.11). Symptoms were
present in 78 of 167 patients (47%) with
plaque on coronary CTA in the absence of
coronary calcium. This difference was also
not statistically significant (p = 0.32) when
compared with patients with a normal calcium score and normal coronary CTA. Seven
of 12 patients (58%) with significant stenosis
and a calcium score of 0 had symptoms,
which was not significant (p = 0.36) either.
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4. CTA in Patients Without Coronary Calcification
Patient motion, heart rate variability, and
poor contrast bolus were causes of limited
studies. Visualization of each vessel (LM,
LAD, RCA, and Cx) including major branches (> 2 mm luminal diameter) was categorized
as excellent, adequate, limited, or poor. Adequate visualization denotes very minimal artifact, but diagnostic-quality images. Limited
evaluation denotes vessels in which mild
plaque might be missed because of artifact.
Poor-quality visualization denotes vessels in
which a hemodynamically significant stenosis
might be missed. In 325 patients with a normal calcium score, 27 (8.3%) had at least one
vessel for which visualization was considered
either limited or poor. In these 27 patients,
visualization of 45 vessel segments was categorized as limited and visualization of 14 segments was characterized as poor. The RCA
was the vessel most commonly characterized
as showing limited or poor visualization.
Discussion
We found a high prevalence of noncalcified plaque in patients with a calcium score
of 0, with fewer than half of the patients in
our study group being disease-free. Considering all 729 calcium score studies, this
yields a false-negative rate of 29% for any
plaque in our patient population and underscores the limitations of calcium scoring.
Although most of these patients had mild
disease, 4% showed a significant stenosis
and eight went on to coronary stenting.
The high prevalence of nonocclusive plaque
(< 50%) found in our study is likely due to the
high sensitivity of coronary CTA for plaque
detection. The true prevalence of subclinical
coronary artery disease in the general population is probably unknown, but it is certainly
high. Autopsy studies have confirmed a high
incidence of noncalcified plaque beginning in
young adults. Strong et al. [17], for example,
found that 47.4% of 30- to 34-year-old adults
autopsied had raised RCA plaques, but only
2.9% had calcified plaques. Clinical heart
disease prevalence increases with age and
has been estimated to be present in 35% of
persons ranging in age from 65 to 74 years
[18]. Given that coronary CTA has been
shown to underestimate plaque burden compared with intravascular sonography [12],
we suspect that the noncalcified plaque burden in our study group may have been even
greater than our results showed.
To our knowledge, only one other study in
the literature has evaluated the presence and
severity of noncalcified plaque on coronary
CTA [19]. In that study, the investigators
found a 2.7% incidence of plaque in patients
without coronary calcification and a 0.5%
incidence of significant stenosis in those patients. Interestingly, normal coronary CTA
findings were seen in 38.5% of the patients,
and calcified plaque was seen in 58.8%. These
findings suggest an almost bimodal distribution of atherosclerotic disease, progressing
from undetectable plaque to calcified plaque
with little intervening isolated soft plaque.
Given the known natural history of plaque,
beginning as fatty streaks in teenagers and
slowly progressing over the course of decades,
a low prevalence of isolated soft plaque is surprising to us. These results differ from those
in our study in which CTA showed 21.7% of
the patients had normal findings, 22.9% had
only noncalcified plaque, and 55.4% had calcified plaque. Although the results of the
Cheng et al. study [19] could be due to selection bias or a large number of low-risk patients, in our experience, detection of small
amounts of soft plaque, particularly in vessels with positive remodeling, requires close
inspection and a high index of suspicion.
The results of other studies have suggested
a high prevalence of noncalcified plaque, par-
ticularly in high-risk patients. The St. Francis Heart Study is one clinical trial that
helped validate the prognostic value of calcium scoring [20]. One of the interesting
findings noted by Arad et al. [20] was the incidence of cardiovascular events in high-risk
patients with the lowest calcium scores.
Whereas low- and intermediate-risk patients
with low calcium scores experienced an
event rate below that predicted by Framingham criteria alone, high-risk patients with
low calcium scores had the same risk predicted by Framingham criteria. This group
presumably includes a high prevalence of
noncalcified plaque. Because this plaque is
not visible on unenhanced CT but is vulnerable to rupture, these patients remained at
high risk for an acute coronary event despite
their low calcium scores.
Calcium scoring has been compared with
catheter angiography in several studies, which
have reported a very high negative predictive
value for significant stenosis [9, 21, 22]. Haberl et al. [22] suggested that the absence of
coronary calcium is highly predictive of the
absence of stenosis, with significant stenosis
in < 1% of patients with a normal calcium
score. Rumberger et al. [8] also found only
one significant stenosis on angiography in 65
patients (1.5%) with a normal calcium score.
The 4% incidence of significant stenosis in
our study is significantly higher than those in
previous reports. Although correlation with
catheter angiography was available in only
eight of these 12 cases, we found excellent
agreement between the two techniques.
Angiographic studies have also documented that acute coronary events are associated with nonstenotic lesions in most cases
[16, 23]. Positive remodeling, the phenomenon of vessel expansion to accommodate intramural plaque, has been associated with
unstable plaques [24, 25]. Remodeling may
A
B
Fig. 2—56-year-old woman who presented for coronary CT angiography because of a strong family history of heart disease.
A, Curved reformatted image from coronary CT angiography shows a large soft plaque in mid left anterior descending artery (arrow).
B, Corresponding catheter angiogram (arrow points to region of plaque seen on coronary CT angiography) did not identify this plaque. In retrospect, there may be mild
narrowing in region of plaque on angiography.
AJR:191, July 2008
53

5. Kelly et al.
mask the size of a lesion on catheter angiography because of the relatively preserved luminal diameter and is a common cause of
plaque underestimation (Fig. 2). Remodeling
also may result in increased surface tension
over a plaque and may alter flow dynamics in
a manner that makes the overlying endothelium more atherogenic. These vulnerable
plaques are most frequently lipid-rich and
infiltrated with inflammatory cells. Currently, intravascular sonography and coronary
CTA are the only imaging techniques available to evaluate the intramural plaque component and positive remodeling. Ideally, future advances in plaque characterization
with coronary CTA and other techniques,
such as molecular imaging and MRI, will allow identification of specific plaques at risk
for imminent rupture.
Because vulnerable plaque generally is
not flow-limiting before undergoing acute
rupture, plaque significance is not related to
the degree of stenosis. Thus, stenosis does
not appear to be useful in identifying patients
at risk for acute myocardial infarction [23].
Medical treatment should focus on patients
with early but detectable disease with a goal
of early plaque stabilization, if not regression. We have found that the calcium score
alone will not detect many patients who
might benefit from medical therapy. Patients
with a normal calcium score (and their physicians) may gain a false sense of security
about the state of their coronary arteries and
may not be as compliant with treatment as
they might otherwise be. This phenomenon
appears to be more common in men, who
were statistically more likely than the women in our study group to have noncalcified
plaque and a normal calcium score.
The real significance of identifying soft
plaque is probably unknown. Presumably,
early identification of this potentially dangerous plaque should be the cornerstone of
atherosclerosis management. Initiation of
med­cal therapy—for the rest of a patient’s
i
lifetime—is a decision that is currently based
on secondary markers, such as low-density
lipoprotein cholesterol (LDL-C) levels. However, just as every child with a sore throat
should not be treated with antibiotics, every
patient with an LDL-C level of > 100 mg/dL
may not need a multidrug treatment regimen.
Conversely, someone with a “normal” lipid
profile may have significant disease and
should receive treatment. Because we now
have a noninvasive means of identifying culprit plaques, we should directly interrogate
54
the coronary arteries rather than rely on secondary markers for determining disease risk.
This is particularly true when the treatment
regimen may involve multiple drugs—statin,
niacin, aspirin, antihypertensives, cholesterol
absorption blockers, fibrates, or omega-3
fatty acids—that are not without risk of side
effects and significant expense to the patient.
Calcium scoring does add useful information for patient risk stratification, as has been
shown in multiple studies [5, 6]. However, in
our patient population, the clinical utility of
a normal calcium score was diminished because of the high false-negative rate. Coronary CTA provides significantly more diagnostic information than the calcium score. In
patients with a 0 calcium score, coronary
CTA was able to identify the large percentage of patients with subclinical disease not
detected by unenhanced CT. In patients with
a positive calcium score, coronary CTA was
able to delineate the presence or absence of
stenosis with a high degree of accuracy. Essentially, coronary CTA adds certainty to the
evaluation of the coronary arteries, whereas
the calcium score generates probabilities.
Perhaps the greatest concerns regarding
coronary CTA are cost and radiation exposure. Considering that the cost of statin therapy alone is at least $1,000 per year in the
United States [26], patients with a negative
coronary CTA examination would recoup
the cost of the examination in 1 year. If imaging were performed at 10-year intervals,
the cost savings could be considerable when
applied to the number of patients eligible for
lipid-lowering therapy.
Radiation exposure is a significant concern with all x-ray-based imaging. In our
patient population, using single-source
64-MDCT scanners, dose modulation, and
retrospective gating, the median patient dose
was 12 mSv. This dose includes the topogram, unenhanced CT for calcium scoring,
timing bolus, and coronary CTA. With the
advent of prospectively gated scanning and
dual-source scanners, the radiation dose of
coronary CTA has the potential to be equivalent to, or less than, that of a calcium score
examination [27]. As the technology evolves,
radiation doses will continue to decline, and
CTA may play a larger role in the detection
of coronary artery disease.
Our study has some limitations. First, our
study group is not a true screening population. There was a high prevalence of disease
in our population, with almost as many patients having a significant stenosis (n = 149)
as those having normal findings (n = 158).
Many of our patients were referred because
either they or their physician had a high suspicion of coronary disease. Forty-seven percent
of referrals were for evaluation of atypical
symptoms, an abnormal stress test, or both.
All asymptomatic patients had at least intermediate risk for coronary artery disease based
on Framingham criteria. However, symptoms
did not significantly correlate with the presence of disease, so our study was not biased
by the number of symptomatic patients.
In clinical practice, workup of many of the
patients in our study would not have included
calcium scoring. The calcium score was determined as part of our routine coronary
CTA, and a number of symptomatic patients
would have undergone invasive angiography
if coronary CTA had not been available. A
normal calcium score would not have precluded further workup in these patients.
However, if all symptomatic patients with a
normal calcium score (n = 143) had undergone invasive angiography, 67 normal angiograms would have been performed. Another
65 patients with mild disease on coronary
CTA would likely have had normal findings
on angiography because low-volume plaque
is often not detectable angiographically.
Thus, 92% of angiograms in symptomatic
patients with a normal calcium score would
have been unlikely to show disease. Also,
five of 12 (42%) significant stenoses—those
without symptoms and without coronary
calcification—would have been undiagnosed. These findings reinforce the diagnostic utility of coronary CTA in the evaluation
of coronary artery disease.
A third limitation is that coronary CTA
was our gold standard for plaque detection.
We do not have corollary imaging for patients who did not undergo angiography. We
also did not evaluate interobserver variability
in the interpretation of stenosis. This would be
most significant in patients with very minimal plaque and in patients with stenosis approaching 50% diameter reduction because
these patients would be the most likely to be
miscategorized. Possibly, some patients with
examinations interpreted as positive for mild
plaque on coronary CTA did not actually have
atherosclerosis. However, in comparing coronary CTA performed using 64-MDCT with
intravascular sonography, Leber et al. [12]
noted a significant trend of CT to underestimate plaque burden and overestimate luminal
diameter. Given these findings, coronary
CTA probably under­ stimated the amount
e
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6. CTA in Patients Without Coronary Calcification
of plaque present in patients with no coronary calcification, and if intravascular sonography had been performed in these patients,
an even greater degree of atherosclerotic disease might have been noted.
Despite the limitations of our study, we
found a considerable atheroma burden in patients with no coronary calcification. In addition, we found a higher incidence of significant stenosis (≥ 50%) than previously reported
in studies comparing invasive angiography
with calcium scoring. Although the calcium
score adds prognostic value to standard risk
factors and serum markers, particularly if
positive, our study shows the value of imaging
the vessel wall directly to identify vulnerable
plaque and to efficiently guide therapy.
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