CAC Serial measurement
CAC progression monitoring is a subject of debate. It is generally not a
recommended measure as no clinical trials have shown demonstrable
benefits of serial CAC measurements; furthermore, there is a lack of
clear data on how CAC progression can be used to guide the choice of
medical therapies.22 A number of studies have been
conducted to assess the effect of statins and other therapies on CAC
progression, with conflicting results. Some have shown a reduction in
calcium scores after statin therapy,23 whereas others
showed that statin therapy was associated with a progression in CAC
scores.24 The postulated mechanism for this
paradoxical effect is that statins increase plaque stability by
increasing calcium content, thereby reducing the chances of progression
to an unstable plaque.25–30 A significant downside of
serial CAC measurement would be recurrent radiation exposure, as the
effective dose for CAC measurement by EBCT is 1 mSv for males and 1.3
mSv for females, and by multi-detector row spiral, CT ranges between
1.5-5.2 mSv for male patients and 1.8-6.2 mSv for female patients, with
even higher effective dose for patients with a body mass index (BMI)
>30.31,32
Nevertheless, repeated measurements of CAC may be warranted in patients
in whom doing so may help guide the clinician. For instance, in those
with a score of zero, measuring CAC score at 5-year may help the
provider in timing the initiation of statin therapy.33