The AHA Guidelines and Scientifi c Statements Handbook
CT coronary angiography to assess noncalcifi c
plaque is not recommended, as there is no prognos-
tic information to determine whether noncalcifi ed
plaque adds any information on top of risk factors,
angiographic disease severity or calcifi ed plaque.
(Level of Evidence: C)
Hybrid scanning (nuclear and CT)
Class III
The incremental benefi t of hybrid imaging strategies
will need to be demonstrated prior to clinical imple-
mentation, as radiation exposure may be signifi cant
with dual nuclear/CT imaging. Therefore, hybrid
nuclear/computed tomographic imaging is not rec-
ommended. (Level of Evidence C)
Ongoing trials
The results from the Multi-Ethnic Study of Athero-
sclerosis [9,10], demonstrates signifi cant predictive
power of coronary artery calcifi cation in a multi-
ethnic, population-based study. This study was not
available at the time of the AHA statement or ACC/
AHA joint statement on coronary calcium and adds
considerable strength to the recommendation for
use as a risk stratifi cation tool. In a study of 6814
persons followed for over 3.5 years, the age, race/
ethnicity, and sex-adjusted HRs (95% CI) for CAC
scores to predict cardiovascular events of 0, 1–99,
100–399, and ≥400 were 1.0, 4.7 (95% CI 2.5–8.7),
11.5 (95% CI 6.2–21.5), and 16.1 (95% CI 8.5–30.8),
respectively. This study found that CAC predicts
subsequent CVD events better than does carotid
intima-media thickness.
Another large population based study is the Heinz
Nixdorf Recall Study [11], an ongoing study in 4800
men and women (47% female) that will assess the
natural history after calcium scoring, as neither the
physician nor the patient will be aware of the calcium
scores. This study will also assess stress testing and
its interplay with coronary calcium testing. The
results of this study should be available in the next
year.
Future directions
Tracking progression of subclinical
atherosclerosis
A proposed use of CACP measurement is to track
atherosclerotic changes over time using serial mea-
surements. There are several published studies of
outcomes related to CACP progression. The fi rst
study demonstrated, in 817 persons, that EBCT-
measured progression was the strongest predictor of
cardiac events [12,13]. This observational study
suggests that continued accumulation of CACP
in asymptomatic individuals is associated with
increased risk of MI in asymptomatic individuals. A
second study measured the change in CACP in 495
asymptomatic subjects submitted to sequential
EBCT scanning. On average, MI subjects demon-
strated an annual rate of CACP change of 42% ±
23%; event-free subjects showed a 17% ± 25% yearly
change (P = 0.0001). The associated relative risk for
acute MI for patients exhibiting ≥15% CACP pro-
gression was elevated 17.2-fold (95% CI: 4.1 to 71.2)
when compared to those without CACP progression
(P < 0.0001).
A large prospective study using EBCT to measure
progression of CACP has been reported. This pro-
spective observational study evaluated 4613 asymp-
tomatic persons aged 50 to 70 years with EBCT
scanning of the coronary arteries at baseline and
again at 2 years and follow-up for 4.3 years [14].
This study demonstrated that the median (inter-
quartile range) calcium score increased by 4 (0, 38)
units from baseline to the year two scan in subjects
who did not sustain a coronary event at any time
during the study. In contrast, median (interquartile
range) calcium scores increased by 247 (40, 471)
units between the baseline and 2-year examinations
in subjects who experienced a fi rst coronary disease
event after the year 2 scan (P < 0.0001). Multiple
logistic regression demonstrated only age (P = 0.03),
male gender (P = 0.04), LDL-cholesterol (P = 0.01),
HDL-cholesterol (P = 0.04), and two-year change in
calcium score (P = 0.0001) were signifi cantly asso-
ciated with subsequent CAD events. Increasing
calcium scores were most strongly related to coro-
nary events in this clinical study, similar to prior
observational studies. Despite this information, it is
diffi cult to justify the incremental population expo-
sure to radiation and cost associated with a repeat
CT test to assess “change” until it is better under-
stood what therapies may be of benefi t and how cli-
nicians should utilize this data in clinical practice.
Several large observational studies, such as MESA
(utilizing both EBCT and MDCT) [9,10] and
RECALL (using EBCT) [11], are currently underway