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Journal of the American College of Cardiology reports that in patients undergoing cardiac computed tomographic angiography (CTA), noncardiac incidental findings are fairly common.

In patients undergoing cardiac computed tomographic angiography (CTA), noncardiac incidental findings are fairly common, reports a study published in the October 13, 2009, issue of the Journal of the American College of Cardiology. However, these findings do not appear to affect noncardiac death rates, and investigating them comes at a cost.

Benjamin J.W. Chow, MD, and colleagues at the University of Ottawa Heart Institute (Ottawa, Canada) assessed 966 prospectively enrolled patients undergoing cardiac CTA at their institution. Radiologists with expertise in thoracic imaging looked at the full field of view available from CT images to identify any noncardiac incidental findings. Mean patient age was 58 years, 55.4% were men, and more than 98% were outpatients. Follow-up was conducted for 18.4 ± 7.6 months.

Based on radiology reports, noncardiac findings were judged to be incidental if they stemmed from an abnormality identified without prior clinical suspicion or in the absence of previously known disease. The findings were classified into 1 of 3 categories:

• Clinically significant: clearly pathological and/or diagnostic, changing patient diagnosis or therapy
• Indeterminate: radiographic abnormalities for which additional investigations or procedures were recommended by the radiologist to clarify diagnosis or for surveillance
• Clinically insignificant

The researchers determined that 401 patients (41.5%) had noncardiac incidental findings: 12 clinically significant, 68 indeterminate, and 321 insignificant. The majority of all noncardiac incidental findings (54%) were pulmonary, including pulmonary nodules, which amounted to 14% of cases.

Impact of Incidental Findings:

Over the length of the study period, none of the indeterminate findings had subsequently been reclassified as clinically significant. Coincidentally, 3 patients in the indeterminate group were later diagnosed with malignant lesions, but these were unrelated to the initial finding. One patient who underwent transthoracic biopsy to investigate an incidental finding suffered a significant complication that resulted in empyema and abdominal abscesses.

Noncardiac death rates were similar in the incidental finding group (n = 7; 1.7%) and in patients with no findings (n = 3; 0.5%). Multivariate analysis showed increasing age to be the only independent predictor of cardiac death.

The total direct cost associated with incidental findings was Canadian $57,596. However, because the analysis only ascertained costs until the time of diagnosis or termination of surveillance, this figure likely “underestimates the total economic impact,” the paper notes. The number “does not include cost of physician follow-up, cost of treatment after diagnosis (eg, surgery or chemotherapy), society costs (eg, lost wages), and patient quality of life.”

Another important issue is that patients with indeterminate findings who undergo further diagnostic investigations are exposed to additional ionizing radiation. Patients in the current study were exposed to a median of 9.4 mSv of additional radiation, according to Dr. Chow and colleagues. Studies of Japanese atomic bomb survivors as well as radiation workers in the nuclear industry suggest exposure levels as low as 5 mSv may be harmful and may increase the risk of cancer, they write.

Balancing Cost, Benefit Over Time:

“The total number of [clinically significant] incidental findings on cardiac CT is small but important. Though incidental findings are relatively common, recommended investigations have potential economic consequences and are not without risk,” the investigators conclude. “In our small cohort, the detection of incidental findings did not appear to predict noncardiac death or cancer death. Larger studies are needed to better understand potential morbidity and mortality benefit of detecting [incidental findings].”

Stephen Balter, PhD, of Columbia University Medical Center (New York, NY), told TCTMD in a telephone interview that the study shows, “in the short term, you’re not going to find anything that is of clinical importance if you look outside the heart.”

One of study’s biggest limitations is its “very short horizon of 18 months,” Dr. Balter commented. “The question then becomes, if you follow the patients out to 5 years, would it make a difference?”

No Clear Answer to Settle Debate:

Dr. Chow said in a telephone interview with TCTMD, that the “bottom line is there’s still no answer” to guide clinical practice. Rather, the study highlights that reporting incidental findings should be “reported with a little bit of forethought as to what the potential consequences are downstream,” he explained. “We just have to be careful and more investigation is needed.”

Current practice is mixed, reported Dr. Chow. Some centers reconstruct a field of view only of the heart, while others will look at the whole chest. “It’s very center dependent,” he said.

In an editorial accompanying the paper, Mark A. Hlatky, MD, of the Stanford University School of Medicine (Stanford, CA), and Carlos Iribarren, MD, MPH, PhD, of Kaiser Permanente of Northern California (Oakland, CA), note that controversy over the optimal management of incidental findings resulting from advanced imaging procedures is not limited to cardiac CT, but also presents vexing questions for brain, abdominal, and whole body imaging.

Due to the lack of professional consensus on how to handle this issue during cardiac CT, Drs. Hlatky and Iribarren advise that the “pros and cons of examining noncardiac structures should be presented fairly to the patient as part of the informed consent process,” so that patients can make the decision about whether to search for incidental findings.

Such an approach is unfeasible, Dr. Balter countered. “Radiologists from day 1 are taught to look at the entire film no matter what the indication. Part of the practice of radiology is not to see why the exam was ordered but to see what else is happening,” he said. “If you use the [imaging] and the data are there, totally ignoring [the data] can be dangerous. This is more of a medical-legal issue.”

Source: Cardiovascular Research Foundation

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