Determinants of Coronary Calcium Conversion Among Patients With a Normal Coronary Calcium Scan: What Is the “Warranty Period” for Remaining Normal?

J Am Coll Cardiol. 2010; 55(11):1110-1117

Min JK, Lin FY, Gidseg DS, Weinsaft JW, Berman DS, Shaw LJ, Rozanski A, Callister TQ

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. 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.

PMID: 20223365

2 Responses

  1. Jacobo Kirsch, MD  on March 15th, 2010

    Very interesting prospective data that definitely adds to our knowledge of the natural history of plaque. Having said that, I do have concerns regarding a recommendation made in this paper:

    For the most part, it is believed that the major benefit of calcium scoring is achieved in patients with an intermediate Framingham risk score. The data in this paper suggests that more than a single calcium score should be obtained in view of the propensity of this measurement to change over time, especially in patients with higher initial scores. But, is this really going to have an impact on how these patients are treated? Or will it only initiate a domino effect of more testing?

  2. Eric M. Dandes  on March 15th, 2010

    I think the issue of coronary calcium is complex! On one hand I think it’s a great screening test, but we really don’t know enough about the prognostic value of serial testing given various scenarios – i.e. whether a patient is treated with drugs (and what type/how long) or just followed-up clinically.

    From a screening viewpoint for someone with an intermediate Framingham risk score, a coronary calcium test is better than a stress test, largely because the latter only picks up obstructive disease, which is less likely to be present in an asymptomatic screened patient.

    Although, if a patient is just followed clinically without treatment, a rise in calcium score more than likely predicts an unfavorable prognosis. However, that argument isn’t as strong in a treatment setting because, increased calcification may signify a conversion of other previously undetected /detected “vulnerable” non-calcified plaque to more “stable” calcified plaque.

    What are some other opinions?


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