One side says there’s not enough evidence to justify incorporating coronary CTA into clinical practice to assess for heart disease. The other side says the use of coronary artery calcium scores can help stratify patients at intermediate risk of disease. Both commentaries in the March issue of JACC Cardiovascular Imaging anchor themselves, albeit in different ways, to the Framingham Risk Score.
Rita F. Redberg, MD, from the University of California at San Francisco, said that the reduction in heart disease in the last two decades “likely is attributable to favorable changes in risk factors” such as cholesterol, blood pressure, smoking and physical inactivity—all defined half a century ago by the Framingham investigators.
In contrast, Redberg said, there are no data to show that coronary CTA is associated with any reduction in coronary heart disease mortality. Redberg acknowledged the high diagnostic accuracy of coronary CTA compared to invasive coronary angiography, but lamented the lack of studies showing an effect of CT on prognosis or on clinical events.
“The images must be shown to offer useful prognostic information incremental to the Framingham Risk Score,” Redberg wrote.
She expressed serious reservations about the American Society of Nuclear Cardiology’s call for more “imaging for prevention,” especially given recent data that suggest the increase in CT imaging from three million scans in 1980 to 62 million scans in 2005 may lead to as many as three million additional cancer cases in the next few decades.
On the other side, Roger S. Blumenthal, MD, and Marietta Ambrose, MD, from The Johns Hopkins Ciccarone Center for Prevention of Heart Disease, said that the Framingham Risk Score leaves a large gap of stratification ambiguity in those assigned to the intermediate category. “Coronary artery calcification scores can refine risk prediction” in these people, they wrote.
Even some people classified by Framingham as low risk are found to have some calcium and studies have demonstrated that any calcium—compared with no calcium—is strongly predictive of cardiac events, they said.
Blumenthal and Ambrose cite the MESA (Multi-Ethnic Study of Atherosclerosis) study which found that coronary artery calcium scores are predictive of all cause mortality in all ethnic groups, with a greater CAC score portending a worse outcome.
“If the clinician is not certain that a particular patient with average or borderline risk factor levels needs to be on life-long aspirin and aggressive lipid-lowering therapy, coronary calcium scoring is a very reasonable option to refine risk assessment and help make that decision,” they said.
In her introduction to the two commentaries, Pamela S. Douglas, MD, from Duke University, said that while the Framingham Risk Score is the gold standard, it “ignores the strong correlations between abnormalities detected by alternative methods [including imaging] and both incident and prevalent coronary artery disease.”
She notes the dearth of prognostic outcomes studies associated with coronary CTA, as well as the financial and logistic hurdles of such studies—making it unlikely they will ever commence. For some, the lack of evidence is a critical flaw; for others, it is a minor detail, a case of “precision versus pragmatism,” she said.