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Patients are usually first
diagnosed with CAD when they:
 |
develop
symptoms, |
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display an abnormal
response to stress testing, or |
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undergo coronary
angiography. |
"Unfortunately, by
that time, the atherosclerotic process is relatively advanced, and many
patients already have experienced myocardial infarction or activity
limiting angina."
NEWS.. Again, by waiting for the
"disease" to manifest itself our window of PREVENTION has been
missed. Medicine has got to get it's near-sighted view of naming a
disease so it can be treated with a drug or surgery...to a far-sighted
view of altering lifestyles so that the "disease" never
manifests itself. One day, by checking our DNA at birth, we will
truly be able to eliminate these later-age-degenerative diseases; but
for now, we have to develop techniques that pickup on diseases before
symptoms appear!
"Coronary artery calcification scanning affords the opportunity to
determine very accurately and noninvasively whether or not underlying
coronary artery disease is present, as well as provide an estimate of
the extent and severity of coronary disease. This information can then
be utilized to optimize patient care, helping to appropriately tailor
prevention goals and to determine further evaluation and follow up, if
needed."
What a scan
looks like:
NORMAL
 No
identifiable plaque
MODERATE
 Definite
plaque burden.
HIGH 
Extensive plaque burden.
Why
Coronary Calcium Scanning?:
"Atherosclerosis is the only process which results in the
deposition of calcium within the walls of arteries. Calcification of the
arterial bed is NOT a degenerative process and is NOT related to the
aging process itself. Indeed, this is a very active metabolic process,
in many ways similar to bone ossification."
Early in the
atherosclerotic process, calcium deposits are very small and difficult
to detect with conventional x-ray imaging, today with CT scanning,
miniscule calcium deposits can be seen easily. Thus, small deposits of
calcium [a score of 10 or more] on a CT scan can be inferred as early
coronary atherosclerosis - this happening way before patients develop
symptoms of coronary disease.
What we can
and cannot learn from a scan:
We CAN learn two facts from a Coronary Scan:
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The presence or
absence of coronary calcium.
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The presence of
ANY coronary calcium signifies that underlying CAD is present. |
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The degree/extent of
calcification.
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The "calcium
score" (a sum of the total size and density of the calcium
deposits found throughout the coronary arteries) provides a
"number evaluation" of the extent of plaque
burden.
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The higher the
"score" the larger the plaque burden and the
higher the risk of subsequent cardiac events in both
symptomatic and asymptomatic patients. |
|
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The "calcium
score" and degree of vessel narrowing does not always agree,
BUT data regarding specific thresholds is given below so that
the score can be used in a clinically meaningful context. |
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We CANNOT learn about very
minimal atherosclerotic changes because early plaque material is not
calcified.
If your score is 0 or
<10 you may still have very early plaque formation that we cannot as
yet see. Following up scans, no matter your score, is important in
the assessment and management of patients.
Calcium
Score Interpretations:
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A
calcium score of 0.
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A calcium score of
0 indicates absence of detected calcium, an extremely low
likelihood of any obstructive CAD, and a good prognosis. |
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A
calcium score <10.
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A score <10 has
been found to have similar clinical implications as a score of 0,
although, clearly, some identifiable plaque is present. |
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A
calcium score >400 |
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Implies the presence
of extensive CAD, with a high likelihood (>90%) of at least one
significantly obstructed vessel (>70% stenosis). Patients with
scores >400, would be considered at high risk for subsequent
development of symptomatic cardiac disease. |
Thus,
a score between 10 and 400:
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Indicates a moderate
plaque burden, and is associated with an intermediate, although
significant risk of future cardiac events, especially when scores
are >100. |
The
Calcium Score odds ratio of developing symptomatic CVD
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scores >50 = 7:1 |
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scores >100 =
20:1 |
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scores >160 =
35:1 |
Predictive
powers of traditional risk factors!
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total cholesterol
>240mg/dl = 1.8:1 |
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HDL<35 = 1.8:1 |
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cigarette smoking =
3.6:1systolic |
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systolic hypertension
= 1.2:1 |
How
age affects Calcium Score Interpretations:
"The clinical significance of a
particular score is influenced by the patients age and gender. A score
of 150 may be "average" for a 70 year old man, but would be
considered markedly abnormal for a 40 year old woman. The correlation
between calcium score and plaque burden is identical in men and women,
however, just as clinical manifestations of CAD are delayed in women as
compared to men, so is the development of coronary calcium. Table 1
displays expected percentile ranges of calcium scores stratified by sex
and age."
"Percentile
Range of Coronary Artery Calcium Score
in Asymptomatic Women and Men as a Function of Age"
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Percentile
Rank
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Women
N=502
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Men
N=1.396
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40-49
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50-59
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60-69
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40-49
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50-59
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60-69
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10
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0
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0
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0
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0
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0
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1
|
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25
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0
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0
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1
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0
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2
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15
|
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50
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0
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0
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20
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1
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30
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100
|
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75
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1
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3
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80
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10
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150
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325
|
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90
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10
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40
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118
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40
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380
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700
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Allopathic
Interpretation of Calcium Scores into further health care:
[NEWS will be posting our "Integrative Interpretations of
Calcium Scores into further health care" at a later date.]
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(1)
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"The presence of any coronary artery calcification,
alone, can impact care significantly, in that secondary
prevention goals may be more appropriate for patient management,
affecting
aggressiveness of lipid lowering, BP therapy, etc. The discovery
of advanced or early coronary calcium may also prompt evaluation
for less "traditional" risk factors, such as serum
homocysteine, Lp(a), and risk factor screening of the patient's
family members.
The discovery of any amount of coronary calcium may provide
strong incentive for the patient to undertake healthy lifestyle
modifications, potentially improving long-term prognosis."
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(2)
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"The calcium
score should influence the decision about whether or not further
cardiac testing is required. Patients with high calcium scores
(>400) should probably undergo stress testing to evaluate for
inducible ischemia. Patients with scores in the intermediate
range require individualized assessment of the need to undergo
further testing (based upon age, clinical presentation, etc)."
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"In the absence of
coronary calcium, no further functional testing is likely to be
required.
These recommendations are summarized in Table 2:"
"Calcium Score Guidelines"
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Calcium
Score
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Plaque
Burden
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Probability
of
Significant
CAD
|
Implications
For CV Risk
|
Recommendations
|
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0
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No identifiable
plaque
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Very low,
generally <5%
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Very Low
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Reassure patient.
Discuss general public health guidelines for primary prevention
of CV disease.
|
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1-10
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Minimal
identifiable plaque burden
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Very
unlikely, <10%
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Low
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Discuss general
public health guidelines for primary prevention of CV diseases
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11-100
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Definite, at least
mild atherosclerotic plaque burden
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Mild or minimal
coronary stenoses likely
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Moderate
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Counsel about risk
factor modification, strict adherence with primary
prevention goals. Daily ASA.
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101-400
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Definite, at least
moderate atherosclerotic plaque burden
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Non-obstructive
CAD highly likely, although obstructive disease possible
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Moderately High
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Institute risk
factor modification and secondary prevention goals. Consider
exercise testing for further risk stratification. Daily ASA
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>400
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Extensive
atherosclerotic plaque burden
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High likelihood
(>90%) of at least one significant coronary stenosis
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High
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Institute very
aggressive risk factor modification. Consider exercise for
pharmacologic nuclear stress testing to evaluate for inducible
ischemia. Daily ASA.
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Allopathic
Indications for Coronary Calcium Scanning:
A Heart CT evaluation may be useful in those patients in whom the
documentation of the presence of CAD would be expected to
change or influence therapy.
|
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Patients with
borderline lipid levels, or mild hypertension may be ideal
candidates, helping stratify whether more aggressive and
expensive secondary prevention therapies are clearly appropriate
for these individuals.
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|
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Patients with a
relatively early family history of coronary disease may benefit
from the enhanced risk stratification offered by Heart CT. If
premature CAD is detected, this may lead to a search for less
"traditional" risk factors, such as homocysteine
levels, Lp(a), and wider screening of family members for these
and other cardiac risk factors.
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|
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In the setting of
dilated cardiomyopathy, Heart CT may be utilized to
noninvasively determine the extent of underlying CAD, helping to
assess whether the cardiomyopathy is likely ischemic in
etiology. A relatively low calcium score would suggest that the
cardiomyopathy is probably idiopathic, viral or metabolic, and
that the patient would not be expected to derive clinical
benefit from undergoing coronary angiography.
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Some centers have
used coronary calcium scanning to help risk stratify patients
who present with chest pain, especially young persons with
atypical symptoms. This may represent another useful, cost
effective application of the technology.
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In general, most
studies have evaluated patients 40-70 years of age, although
younger individuals may be appropriate candidates depending upon
their risk factor profile. Incremental clinical benefit is
unlikely to be substantial in individuals over the age of 70,
and generally Heart CT is not recommended in these individuals."
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Allopathic
Contraindications [clinical]:
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There is no data
to support mass imaging of asymptomatic individuals at the
present time.
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|
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Patients who
already have documented CAD are not appropriate for Heart CT
evaluation. The results of the scan would not be expected to
change management in this patient population."
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Allopathic
Contraindications [procedural]:
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Scanning is
accomplished at rest, without contrast administration, without
the need for iv access, and in a nonfasting state. No changes in
patient medication are required. There are no restrictions with
respect to pacemakers or prosthetic devices.
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|
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Patients with
arrhythmias (chronic atrial fibrillation, very frequent
extrasystoles) or patients with relative resting tachycardia
(HR>90-95 bpm) should not undergo Heart CT scanning, because
adequate cardiac gating will be difficult to accomplish,
compromising image quality.
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|
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Because scanning
does involve minimal x-ray exposure, women who are pregnant or
potentially pregnant should not undergo this evaluation."
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Allopathically,
how does Heart CT fit in with other cardiac tests?
Heart CT's major role is in providing extremely sensitive assessment of
the presence of early CAD, and extent of plaque burden. Compared to
other imaging modalities, Heart CT is not as helpful in defining
location of significant coronary stenoses or in defining clinical
prognosis.
The most powerful cardiology tool for defining clinical prognosis is
nuclear stress testing, and therefore patients with significant coronary
calcium deposition should be preferentially considered for an exercise
or pharmacologic nuclear stress testing for further evaluation.
In general, echocardiography is superior for evaluating valvular
structures and valvular function. Although left ventricular function
assessment is possible with CT scanning, this involves contrast
infusion, a less than desirable requirement in view of the potential
side effects of iodinated contrast administration.
Heart CT is not a replacement for coronary angiography. At the present
time, coronary angiography represents the only reliable technology to
accurately assess luminal narrowing within the coronary circulation.
Cardiac CT scanning may be utilized to evaluate the pericardium in
patients with suspected constrictive pericarditis, and may be useful in
evaluating the right ventricle in rare patients with suspected right
ventricular dysplasia. For nearly all other indications, non-CT imaging
modalities are more appropriate and/or clinically useful."
"Bibliography
Wexler L, Brundage B, Crouse J,
Detrano R, et al. Coronary artery calcification: pathophysiology,
epidemiology, imaging methods, and clinical implications. A statement
for health professionals from the American Heart Association.
Circulation 1996;94:1175-1192.
Rumberger JA, Brundage BH, Rader DJ, Kondos G. Electron beam computed
tomographic coronary calcium scanning: a review and guidelines for use
in asymptomatic persons. Mayo Clin Proc 1999;74:243-252.
Janowitz WR, Agatston AS, Kaplan G, Viamonte M. Differences in
prevalence and extent of coronary artery calcium detected by ultrafast
computed tomography in asymptomatic men and women. Am J Cardiol
1993:72:247-254.
Simons DB, Schwarz RS, Edwards WD, Sheedy PF, et al. Noninvasive
definition of anatomic coronary artery disease by ultrafast computed
tomographic scanning: a quantitative pathologic comparison study. J Am
Coll Cardiol 1992;20:1118-1126.
Guerci AD, Spadaro LA, Goodman KJ, Liedo-Parez A, et al. Comparison of
electron beam computed tomography scanning and conventional risk factor
assessment for the prediction of angiographic coronary artery disease. J
Am Coll Cardiol 1998;32:673-679.
Rumberger JA, Behrenbeck T, Breen JF, Sheedy PF. Coronary calcification
by electron beam computed tomography and obstructive coronary artery
disease: a model for costs and effectiveness of diagnosis as compared
with conventional
cardiac testing methods. J Am Coll Cardiol 1999;33:453-462.
Comparison of Electron Beam and Helical CT in the Detection of Coronary
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