Cardiac CT yields significant extracardiac findings

Nov 25, 2006

CHICAGO - Cardiac CT yields a high number of incidental findings, many of them clinically important, according to a study presented Sunday at the 2006 RSNA meeting.

Medical student Florian Mayer and his colleagues at the Medical University of South Carolina in Charleston analyzed 964 CT cardiac imaging studies acquired over a two-year period, including 241 calcium scoring studies, 425 coronary CT angiography (CTA) studies, 176 evaluations for pulmonary stenosis following radiofrequency ablation, and 122 evaluations of coronary artery bypass grafts (CABG).

"We retrospectively reviewed the radiology reports," Mayer said in his RSNA presentation of the group's findings.

The researchers classified the findings into four groups: 1) emergent findings requiring immediate clinical evaluation, including acute dissection, pulmonary embolism and pneumonia; 2) findings requiring urgent follow-up, including pulmonary nodules 1 cm and larger, aortic aneurysm, and other lesions suspicious for neoplasm; 3) important but not urgent findings, including pulmonary nodules 1 cm and smaller, interstitial lung disease, pleural effusion, and indeterminate liver or adrenal lesions; and 4) incidental lesions needing no specific follow-up including benign liver or adrenal lesions and subsegmental atelectasis, and emphysema.

The group detected a total of 323 extracardiac findings in 291 patients (30.2%), including 190 patients (19.7%) with findings requiring follow-up (categories 1-3).

"In the calcium scoring group, we had 27 findings in 241 patients (11.2%)," Mayer said. Of these, two category 1 or 2 findings included an aortic aneurysm. In the coronary CTA group, there were extracardiac findings in 156 of the 425 patients (36.7%).

"Twenty-nine of these (CTA) findings were emergent or urgent findings, such as nodules larger than 1 cm or pulmonary emboli, and 75 were category 3 findings, such as nodules smaller than 1 cm or interstitial lung disease," he said.

Incidental findings were seen in 54 of 176 patients (30.7%) evaluated for pulmonary vessel stenosis following radiofrequency ablation, and in 54 of 122 (44.3%) CABG patients.

Urgent or emergent findings (categories 1 and 2) were seen in 0.8% of calcium scoring patients, 6.8% of coronary CT angiography patients, 1.7% of patients evaluated for pulmonary stenosis following ablation, and 4.1% of CABG patients.

One 55-year-old patient presented with substernal chest pain after CABG surgery. The cause of her pain could be seen on the CT image, which showed that the surgeon had left "a needle in the body," Mayer said. Esophageal cancer, lung cancer, and aortic aneurysm were the most clinically serious findings detected at cardiac CT.

"Incidental findings occurred significantly more frequently in cardiac CTA studies compared to calcium scoring (p < 0.001%) with no significant differences in findings between CTA and bypass grafts," he said.

Study limitations included the practice of reviewing radiology reports, which may have underestimated the true incidence of findings. Also, some findings may have been previously documented, which calls into question their true clinical significance, Mayer said.

There was no significant relationship between the indication and the findings, he added.

As for why CTA produced so many more findings per patient than calcium scoring, Mayer said that most patients undergoing CTA have symptoms and therefore may represent a higher-risk population.

Routine follow-up is not indicated for lung nodules 1 cm or smaller, so by this measure some findings may have been overstated, an audience member commented.

By Eric Barnes
AuntMinnie.com staff writer
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