Coronary-Artery Calcium (CAC) imaging

CAC screening improves CAD risk factors without increasing downstream costs: EISNER

March 24, 2011 |                                 Michael O'Riordan

Los Angeles, CA - New data from the Early Identification of Subclinical Atherosclerosis by Noninvasive Imaging Research (EISNER) study show that noninvasive imaging may actually lead to clinically meaningful improvements in coronary artery disease (CAD) risk factors in healthy individuals. Compared with individuals who did not undergo coronary-artery calcium (CAC) imaging, screening of subclinical atherosclerosis with CAC screening led to an improvement in systolic blood pressure, LDL-cholesterol levels, and a reduction in waist circumference as well as a trend toward greater weight loss among overweight individuals.

The improvements occurred without a significant increase in downstream medical costs, suggesting that CAC screening can play a "gatekeeper" role in determining a need for further noninvasive testing, say investigators.

"We wanted to find out how much impact the scan had on the way that patients take care of themselves, the way they think about changing their lifestyle and doing something about preventing heart disease," senior investigator Dr Daniel Berman (Cedars Sinai Medical Center, Los Angeles, CA) told heartwire. "There have been other studies suggesting an impact on how patients behave after seeing their scan, that as the amount of calcium on the scan went up, patients began to do more about changing their behavior. We noticed the same thing: patients who had a lot of calcium were more likely to do all the things that would prevent heart disease than patients who had less amounts of calcium. Also, the calcium-scoring group did more to change their lifestyle than the patients who did not undergo coronary scanning."

Published online March 23, 2011 in the Journal of the American College of Cardiology with first author Dr Alan Rozanski (St Luke's Roosevelt Hospital, New York), the study included 2137 healthy volunteers randomized to undergo CAC scanning or no coronary-calcium screening. Individuals in the trial were middle-aged and had CAD risk factors but did not have a history of cardiovascular disease.

Change in blood pressure and LDL cholesterol

Of the seven measured risk factors, investigators observed improvements in systolic blood pressure, LDL cholesterol, and a reduction in waist circumference among those who underwent CAC screening.  There was no difference in serum glucose levels, exercise levels, or smoking status between the two treatment arms at four years. CAD risk, as assessed by the Framingham Risk Score (FRS), increased in the no-scan volunteers but remained stable among those who received the CAC scan.

Individuals with higher amounts of calcium were patients who made the larger amount of change.

"Individuals with higher amounts of calcium were patients who made the larger amount of change," said Berman.

The incurred medical costs did not significantly differ between the two treatment arms, with procedure and medication costs totaling $3649 among those who did not undergo CAC screening and $4063 among those who did. The total incurred costs did differ by the amount of coronary calcium observed on the scan, however, with patients having a CAC score >400 significantly more likely to incur more procedural and medication costs than those with less coronary calcium. 

"Overall, in the scanned group vs the no-scan group, the downstream testing costs were similar," Berman told heartwire. "Interestingly, when you look at patients without any coronary calcium, their downstream testing costs were low. Patients who had a lot of calcium, it would be more common for them to go on to additional testing."

Change in clinical risk factors and all incurred medical costs

Parameter	No CAC scan	CAC scan	p
Systolic blood pressure (mm Hg)
Baseline	130	131	0.03
Change from baseline	-5	-7	0.02
LDL cholesterol (mg/dL)
Baseline	130	133	0.15
Change from baseline	-11	-17	0.04
Waist circumference (in)
Baseline	41.0	41.3	0.19
Change from baseline	1	0	0.01
All costs ($)	3649	4063	0.09

Incurred costs according to CAC score

Medical costs	CAC score 0	CAC score 1-99	CAC score 100-399	CAC score >400	p (trend)
All costs ($)	2623	4394	4900	9309	<0.001

Overall, there was no significant difference in the number of performed procedures among patients who underwent CAC screening. There was a trend toward more lipid-lowering medications being prescribed among those randomized to CAC screening and a significant difference in the number of new blood-pressure-lowering medications prescribed.

In a comparison between volunteers with no observable calcification on the CAC scan with those who did not undergo CAC screening, those with a CAC score of zero were significantly less likely to undergo any stress testing at four years as well as less likely to undergo cardiac catheterization and coronary revascularization. The low-CAC-score patients also incurred significantly less medical costs ($2623 among those with a CAC score of zero vs $3649 for those who did not undergo screening; p<0.001).

The results of the EISNER analysis contrast with the results of a meta-analysis published online March 14, 2011 in the Archives of Internal Medicine. As reported by heartwire, Dr Daniel G Hackam (University of Western Ontario, London) and colleagues assessed seven relevant studies and found no significant changes in the use of drug therapies, exercise, dietary therapy, smoking cessation, or diagnostic coronary catheterization or revascularization based on the results of carotid ultrasound, CAC scans, or other noninvasive imaging techniques.

To heartwire, Berman said that the EISNER data provide support for the recent American College of Cardiology Foundation (ACCF)/American Heart Association (AHA) class IIa recommendation for the use of computed tomography (CT) to measure coronary calcium. According to the ACCF/AHA, the use of CAC "is reasonable for cardiovascular risk assessment in asymptomatic adults at intermediate risk (10% to 20% 10-year risk)."

Berman has research grants from Siemens and GE/Amersham and has both research grants from and is on the speaker's bureau of Astelles and Lantheus.

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Sources

1. Rozanski A, Gransar H, Shaw LJ, et al. Impact of coronary artery calcium scanning on coronary risk factors and downstream testing. J Am Coll Cardiol 2011; DOI:10.1016/j.jacc.2011.01.019. Available at: http://content.onlinejacc.org.
2. Hackam DG, Shojania KG, Spence JD, et al. Influence of noninvasive cardiovascular imaging in primary prevention: Systematic review and meta-analysis of randomized trials. Arch Intern Med 2011; DOI:10.1001/archinternmed.2011.69. Available at: http://archinte.ama-assn.org.