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Calcium in Colon Scan Indicates Cardiac Risk: Presented at RSNA

By Ed Susman

CHICAGO, IL -- December 2, 2004 – Information gathered through computed tomography (CT) of the colon could help identify patients who have calcium deposits in the aorta and who are therefore at risk of developing cardiovascular events.

A high calcium score at the bifurcation of the aorta "is an independent risk factor for cardiovascular disease," said Jesse Davila, MD, fellow in musculoskeletal radiology, Mayo Clinic, Jacksonville, Florida, United States.

A total calcium score above the 75th percentile or a calcium score in the aorta above the 75th percentile for that area, detected while performing a virtual colonoscopy can be warning signs of cardiovascular disease, he said during a presentation here December 1^st at the Radiological Society of North America (RSNA) 90^th Scientific Assembly and Annual Meeting.

Dr. Davila and colleagues reviewed data on 480 patients who underwent CT colonography between 1995 and 1998. Data from 467 of those patients was analyzed. The average age of the patients was 64, and 205 of them were women.

Using the CT colonography data, the researchers obtained images of half the body that provided a view of artifacts outside the colon. The researchers were able to detect extracolonic findings in most of the subjects studied, Dr. Davila said in a press briefing, "and in 13% those findings were significant." The CT colonography in these subjects revealed renal cell carcinoma, abdominal aortic aneurysm, lung cancer and ovarian cysts.

Coronary artery calcification data was obtained with SmartScore CT scanning technology (GE Medical Systems), using a threshold of more than 150 Hounsfield units (HU) for the abdominal aorta, he said.

"We decided to quantify the calcium findings in the aorta and stratify calcium by total score, as well as scores in suprarenal, laminar, and bifurcation segments," he said. In general, the highest calcium scores were found in the laminar area, but "these scores did not correlate with a statistically significant increased risk," he said. By contrast, a total calcium score or bifurcation score above the 75th percentile "correlated with a 10-fold increase in risk of cardiac event," he said.

There were nine cardiac events -- eight myocardial infarctions and one death -- during 5 years of follow-up in this group of subjects.

The mean total baseline calcium score was 977 HU and total or bifurcation score of 3558 HU or higher correlated with increased risk," he said.

Since colon exam is recommended after age 50 -- and heart disease risk also increases with age -- CT colonography has the potential to identify patients that otherwise would go undetected, he said.

Michael Brant-Zawadski, MD, medical director of radiology, Hoag Memorial Hospital, Newport Beach, California, United States, said the study strengthens the case for CT colonography "since it really is a half body scan that can provide many useful incidental findings." Dr. Brant-Zawadski moderated the press briefing for the RSNA

He added that it could provide information that is not available using traditional risk factors. "For example, a major component of the Framingham Risk Score is age, because the risk of cardiovascular disease increases with age. But if you have a 75-year-old with high Framingham score and zero calcium in the aorta, you can probably downshift his risk. On the other hand a 60-year-old with a much lower Framingham score but a high calcium score should probably have his risk up-shifted."


[Presentation title: "Assessment of Cardiovascular Risk Status at CT Colonography." Poster 1552VI-p]

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