Chapter 20 Cardiac CT Imagingcoronary atherosclerosis and provide a rationale for
intensifi ed LDL-lowering therapy” [2]. A Clinical
Expert Consensus Document of the American
College of Cardiology published in 2007 [3],
specifi ed that coronary calcium measurements in
clinically-selected intermediate CAD risk patients
(e.g., those with a 10–20% Framingham 10-year risk
score) was a reasonable option to refi ne clinical risk
prediction and to select patients for altered targets
for lipid-lowering therapies. Results from ongoing
studies (listed below) should strengthen the recom-
mendation, as the results of these trials were unavail-
able at the time of writing the current guidelines.
ACC/AHA Expert Consensus Document on
coronary calcium
- The Committee judged that it was appropriate to
consider use of CAC measurement in such [inter-
mediate risk] patients based on available evidence
that demonstrates incremental risk prediction infor-
mation in this selected patient group. This conclu-
sion is based on the possibility that such patients
might be reclassifi ed to a higher risk status based on
high CAC score, and subsequent patient manage-
ment may be modifi ed. - The Committee does not recommend use of CAC
measurement in patients with low CHD risk (below
10% 10-year risk of estimated CHD events). - The Committee does not advise CAC measure-
ment in asymptomatic patients with high CHD risk
(greater than 20% estimated 10-year risk of esti-
mated CHD events, or established coronary disease,
or other high-risk diagnoses). This selected patient
stratum are already judged to be candidates
for intensive risk reducing therapies based on
current National Cholesterol Education Program
guidelines. - Current clinical practice guidelines indicate that
patients classifi ed as high risk based on high risk
factor burden or existence of known high-risk
disease states (e.g., diabetes) are regarded as candi-
dates for intensive preventive therapies (medical
treatments). There is no clear evidence that addi-
tional noninvasive testing in this patient population
(high coronary calcium score e.g., CAC >400) will
result in more appropriate selection of treatments. - Evidence indicates that symptomatic patients con-
sidered to be at low risk of coronary disease by virtue
of atypical cardiac symptoms may benefi t from CAC
testing to help in ruling out the presence of obstruc-
tive coronary disease. Other competing approaches
are available, and most of these competing modali-
ties have not been compared head-to-head with
CAC.Comparison with European Guidelines
The recommendations from the AHA and ACC are
very similar to those of the European guidelines [4].
The European guidelines state, “The resulting
calcium score is an important parameter to detect
asymptomatic individuals at high risk for future
CVD events, independent of the traditional risk
factors.” The guidelines state that calcium scanning
should be used as a tool to improve risk assessment
in individual patients. This organization further
acknowledged that the prognostic relevance of CAC
has been demonstrated in several prospective studies,
not only in asymptomatic individuals but also
in patients undergoing coronary angiography.
However, screening for CAC should be reserved to
individuals at intermediate risk and in men older
than 45 years and women older than 55 years.
British Cardiovascular Society (BCS) Working
Group recommendations for CT [5]. Currently, the
role of MDCT in clinical practice is reserved for
patients who following other noninvasive investiga-
tions remain a diagnostic problem, or where the
angiogram has failed to identify proximal coronary
anatomy, for example, failure to obtain detailed
assessment of the coronary ostia or grafts.
In selected patients, the disadvantage of the radia-
tion dose can be balanced by specifi c valuable informa-
tion it provides. The number of patients likely to fulfi ll
such criteria (confi rmation of suspicion of CAD) is
probably in the order of 10% of all those presenting to
the cardiologist/cardiovascular physician.
Another area in which MDCT may play an
increasing important role is in the diagnosis of
patients presenting with acute chest pain. The “triple
scan” in which pulmonary embolus, acute coronary
syndromes and aortic dissection are excluded in
a single examination performed in less than 10
minutes from start to fi nish is an exciting concept,
and may well have a major impact on management
in the future. Added to the ability to assess LV func-
tion, this technique may well become the fi rst-line
investigation in the future.