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