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Determinants of coronary calcium conversion among patients with a normal coronary calcium scan: what is the "warranty period" for remaining normal?

The present study focuses on the natural history of coronary calcifications. Interestingly, approximately 25% of the initial negative study group “converted” to positive scans. However, this may also reflect the well known relatively high “interscan variability”. Nevertheless, age, smoking and diabetes were independent predictors for a conversion to a positive scan after 4,1 years. 
Non-Invasive Imaging


OBJECTIVES:
This study identified the incidence and predictors of conversion of a normal to abnormal coronary artery calcium (CAC) scan during serial CAC scanning over 5 years.
BACKGROUND: Although a normal CAC scan signifies absence of significant atherosclerosis and is used to identify individuals at low clinical risk, the "warranty period" of a normal CAC scan relative to its ability to predict sustained absence of coronary atherosclerosis remains unknown.

METHODS:
We assessed frequency of and time to progression, as well as proportional increase of CAC in 422 individuals with normal CAC scan (CAC = 0) undergoing annual CAC scanning for 5 years. Results were compared with those of a referent cohort of 621 individuals with baseline CAC scan (CAC >0).

RESULTS:
A total of 106 (25.1%) patients with CAC = 0 developed CAC during follow-up at a mean time to conversion of 4.1 +/- 0.9 years. Incidence of conversion to CAC >0 was nonlinear and was highest in the fifth year. In multivariable analysis, progression to CAC >0 was associated with age, diabetes, and smoking (p < 0.01 for all). Among the 621 individuals with baseline CAC >0, only the presence of CAC itself, rather than CAD risk factors, was predictive of CAC progression. Among propensity score-matched individuals with CAC >0 versus CAC = 0, baseline CAC >0 emerged as the strongest predictor of CAC progression (hazard ratio [HR]: 12.50, 95% confidence interval [CI]: 9.31 to 16.77), followed by diabetes (HR: 2.07, 95% CI: 1.47 to 2.90) and smoking (HR: 1.29, 95% CI: 1.02 to 1.63, p < 0.05 for all).

CONCLUSIONS:
Among individuals with CAC = 0, conversion to CAC >0 is nonlinear and occurs at low frequency before 4 years. No clinical factor seems to mandate earlier repeat CAC scanning.

References


J Am Coll Cardiol. 2010 Mar 16;55(11):1110-7
The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.

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