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Coronary artery calcium scoring: Its practicality and clinical utility in primary care

Cleveland Clinic Journal of Medicine. 2018 September;85(9):707-716 | 10.3949/ccjm.85a.17097
September 4, 2018|Cleveland Clinic Journal of Medicine
Parth Parikh, MD;Nishant Shah, MD;Haitham Ahmed, MD, MPH;Paul Schoenhagen, MD;Maan Fares, MD
Author and Disclosure Information

Parth Parikh, MD
Department of Internal Medicine, Cleveland Clinic; Clinical Instructor of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH

Nishant Shah, MD
Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic

Haitham Ahmed, MD, MPH
Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic; Assistant Professor, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH

Paul Schoenhagen, MD
Department of Diagnostic Radiology, Imaging Institute, and Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic; Professor, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH

Maan Fares, MD
Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic; Assistant Professor, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH

Address: Maan Fares, MD, Department of Cardiovascular Medicine, J2-4, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; faresm@ccf.org

ABSTRACT

Coronary artery calcium scoring is useful as a risk-stratification tool in coronary artery disease, and it outperforms other risk-assessment methods. American College of Cardiology/American Heart Association guidelines give the test a IIB recommendation in clinical scenarios in which risk stratification is uncertain. However, if the test is not used in the appropriate clinical setting, misinterpretation of the results can lead to unnecessary cardiac testing. This review provides the primary care provider with basic knowledge about the test’s clinical utility, interpretation, risks, and limitations.

KEY POINTS

  • Coronary artery calcium testing is useful in diagnosing subclinical coronary artery disease and in predicting the risk of future cardiovascular events and death.
  • Given the high negative predictive value of the test, it can also serve to reclassify risk in patients beyond traditional risk factors.
  • Along with shared decision-making, elevated calcium scores can guide the initiation of statin or aspirin therapy.
  • A high score in an asymptomatic patient should not trigger further testing without a comprehensive discussion of the risks and benefits.

 

    CALCIUM SCORING AS A DIAGNOSTIC TOOL

    Early multicenter studies evaluated the utility of calcium scoring to predict coronary stenosis in patients who underwent both cardiac CT and coronary angiography. The sensitivity of calcium scoring for angiographically significant disease was high (95%), but its specificity was low (about 44%).18

    Budoff et al,19 reviewing these and subsequent results, concluded that the value of calcium scoring is its high negative predictive value (about 98%); a negative score (no calcification) is strongly associated with the absence of obstructive coronary disease.

    Blaha et al20 concluded that a score of 0 would indicate that the patient had a low risk of cardiovascular disease. A test with these characteristics is helpful in excluding cardiovascular disease or at least in determining that it is less likely to be present in a patient deemed to be at intermediate risk.

    CALCIUM SCORING AS A PROGNOSTIC TOOL

    Early on, investigators recognized the value of calcium scoring in predicting the risk of future cardiovascular events and death.21–25

    Predicting cardiovascular events

    Pletcher et al21 performed a meta-analysis of studies that measured calcification in asymptomatic patients with subsequent follow-up. The summary-adjusted relative risk of cardiac events such as myocardial infarction, coronary artery revascularization, and coronary heart disease-related death rose with the calcium score:

    • 2.1 (95% confidence interval [CI] 1.6–2.9) with a score of 1 to 100
    • 4.2 (95% CI 2.5–7.2) with scores of 101 to 400
    • 7.2 (95% CI 3.9-13.0) with scores greater than 400.

    The meta-analysis was limited in that it included only 4 studies, which were observational.

    Kavousi et al,22 in a subsequent meta-analysis of 6,739 women at low risk of atherosclerotic cardiovascular disease based on the American College of Cardiology/American Heart Association (ACC/AHA) pooled cohort equation (10-year risk < 7.5%), found that 36.1% had calcium scores greater than 0. Compared with those whose score was 0, those with higher scores had a higher risk of atherosclerotic cardiovascular disease events. The incidence rates per 1,000 person-years were 1.41 vs 4.33 (relative risk 2.92, 95% CI 2.02–3.83; multivariable-adjusted hazard ratio 2.04, 95% CI 1.44–2.90). This study was limited because the population was mostly of European descent, making it less generalizable to non-European populations.

    Calcium scoring has also been shown to be a strong predictor of incident cardiovascular events across different races beyond traditional risk factors such as hypertension, hyperlipidemia, and tobacco use.

    Detrano et al,23 in a study of 6,722 patients with diverse ethnic backgrounds, found that the adjusted risk of a coronary event was increased by a factor of 7.73 for calcium scores between 101 and 300 and by a factor of 9.67 for scores above 300 (P < .001). A limitation of this study was that the patients and physicians were informed of the scores, which could have led to bias.

    Carr et al24 found an association between calcium and coronary heart disease in a younger population (ages 32–46). In 12.5 years of follow-up, the hazard ratio for cardiovascular events increased exponentially with the calcium score:

    • 2.6 (95% CI 1.0–5.7, P = .03) with calcium scores of 1 through 19
    • 9.8 (95% CI 4.5–20.5, P < .001) with scores greater than 100.

    Predicting mortality

    Budoff et al,25 in an observational study of 25,253 patients, found coronary calcium to be an independent predictor of mortality in a multivariable model controlling for age, sex, ethnicity, and cardiac risk factors (model chi-square = 2,017, P < .0001). However, most of the patients were already known to have cardiac risk factors, making the study findings less generalizable to the general population.

    Nasir et al26 found that mortality rates rose with the calcium score in a study with 44,052 participants. The annualized mortality rates per 1,000 person-years were:

    • 0.87 (95% CI 0.72–1.06) with a score of 0
    • 2.97 (95% CI 2.61–3.37) with scores of 1–100
    • 6.90 (95% CI 6.02–7.90) with scores of 101–400
    • 17.68 (95% CI 5.93–19.62) with scores higher than 400.

    The mortality rate also rose with the number of traditional risk factors present, ie, current tobacco use, dyslipidemia, diabetes mellitus, hypertension, and family history of coronary artery disease. Interestingly, those with no risk factors but a calcium score greater than 400 had a higher mortality rate than those with no coronary calcium but more than 3 risk factors (16.89 per 1,000 person-years vs 2.72 per 1,000 person years). As in the previous study, the patient population that was analyzed was at high risk and therefore the findings are not generalizable.

    Shaw et al27 found that patients without symptoms but with elevated coronary calcium scores had higher all-cause mortality rates at 15 years than those with a score of 0. The difference remained significant after Cox regression was performed, adjusting for traditional risk factors.

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