The AHA Guidelines and Scientifi c Statements Handbook
Table 20.3 Sensitivity and specifi city of diagnostic tests for evaluation of CAD
No. of patients Sensitivity (%) Specifi city (%)Stress treadmill^8524565271
Exercise SPECT85,86 4480 87 73
Stress echocardiography^8526378577
EBCT calcium22,23,89 5730 85 75
Cardiac CT Angiography – Scientifi c
Statement 2006
CT angiography is rapidly becoming a standard tool
in the outpatient evaluation of coronary artery
disease. The improved resolution and number of
detectors has made this test highly accurate com-
pared to invasive angiography. In a meta-analysis
comparing CTA to MRA [6], a comparison of sen-
sitivity revealed higher diagnostic accuracy for
MDCT (weighted [by the proportional sample size]
average: 82%, 95% CI: 79–90%) when compared
with MRA (weighted average: 75%, 95% CI: 60%–
84%, P = 0.029).
A recent meta-analysis by Stein et al. [7] reported
the average sensitivity and specifi city values were
95% and 84% for 4-slice CT and noted a high diag-
nostic accuracy for both 16- and 64-slice CT. Diag-
nostic specifi city values were 90% or higher for
proximal, mid, and distal segments. These diagnos-
tic values are very favorable compare to current
noninvasive imaging techniques, such as nuclear or
echocardiographic stress testing (Table 20.3).
For patients with a clinical suspicion of obstruc-
tive CAD, the high negative predictive value (>98%
in most studies) may be useful to obviate the need
for invasive coronary angiography in patients in
whom symptoms or an abnormal stress test result
require to rule out the presence of coronary artery
stenoses. Especially if symptoms, age, and gender
suggest a low to intermediate probability of hemo-
dynamically relevant stenosis [8] ruling out hemo-
dynamically relevant stenoses by CT coronary
angiography may be clinically useful and may help
avoid invasive angiography.
While utility of this tool for coronary anomalies
and bypass grafts has been established, the utility of
this tool to assess stent patency and assessment of
noncalcifi c plaque still needs to be established. At
the time of the AHA 2006 statement (Table 20.4),
radiation exposure doses for cardiac CT were in
the 10–18 mSev range (similar to nuclear imaging
doses). New techniques to lower radiation dose and
contrast requirements continue to be developed,
and will be important in the future implementation
of this tool in larger populations. Radiation dose
reduction techniques (available since the AHA state-
ment of 2006) include: dose modulation (lowers
radiation dose 30–48%); reduction of kVp to 100 for
thinner patients (lowers radiation dose by 40%),
limit top and bottom of scan fi eld (lowers radiation
dose by 20%) and prospective triggering (lowers
radiation dose by 70%). Use of all of these tech-
niques results in CT angiograms with doses as low
as 1 mSev (lower than coronary angiography).Hybrid imaging with CT and nuclear
imaging
Currently available and an area of ongoing clinical
research is the application of hybrid PET-CT and
SPECT-CT scanners. This will allow for the acquisi-
tion of metabolic and/or perfusion information as
well as anatomic data including both coronary calci-
fi cation as well as angiographic data. The incremental
benefi t of hybrid imaging strategies will need to be
demonstrated prior to clinical implementation, as
radiation exposure may be signifi cant with dual
nuclear/CT imaging. At this time there is no data
supporting the use of hybrid scanning to assess car-
diovascular risk or presence of obstructive disease.Recommendations
CT angiography
Class IIa
CT coronary angiography is reasonable for the
assessment of obstructive disease in symptomatic
patients. (Level of Evidence: B)