Incidental findings appear in 20% of coronary CT studies

November 1, 2007

It's not unusual for imagers to spot incidental findings when clearing chest pain patients of obstructive coronary artery disease with CT angiography. But few data exist on unsuspected disease in patients with known ischemia or those undergoing heart surgery. In one of the first studies of its kind, researchers at the University of Maryland have found that the frequency of clinically relevant cardiac and noncardiac conditions found incidentally on these patients is much higher than previously thought. They suggest that CTA could turn into a valuable postprocedural management tool in this patient population.

It's not unusual for imagers to spot incidental findings when clearing chest pain patients of obstructive coronary artery disease with CT angiography. But few data exist on unsuspected disease in patients with known ischemia or those undergoing heart surgery. In one of the first studies of its kind, researchers at the University of Maryland have found that the frequency of clinically relevant cardiac and noncardiac conditions found incidentally on these patients is much higher than previously thought. They suggest that CTA could turn into a valuable postprocedural management tool in this patient population.

In a retrospective analysis, Dr. Jeffrey Mueller and colleagues found nearly 20% of 259 patients who underwent coronary bypass grafting had at least one unsuspected but potentially dangerous condition unrelated to their coronaries or coronary bypass grafts (AJR 2007;189:414-419).

It is reasonable to expect that some cardiac surgery patients may also suffer from pulmonary emboli, but the PE rate in this population was surprisingly high. The connection is not well known in the radiology community, said senior investigator Dr. Charles S. White, chief of thoracic radiology. While this study involved a 16-slice scanner, anecdotal evidence suggests the same results with a relatively new 64-slice CT.

Common incidental cardiac findings included moderate or large pericardial effusion, intracardiac thrombi, and substantial paracardiac or mediastinal hemorrhage. Common incidental noncardiac findings included pulmonary nodules, pneumonia, and tracheal or lobar mucous plugging.

Additional studies with larger groups of patients and longer follow-up should add weight to these findings. For now, the paper helped fuel the debate on whether imagers should reconstruct all cardiac CTA studies on a wide field-of-view to capture potential disease in the entire thorax, as some scanners permit and some practitioners of cardiac CTA advocate, or keep interpretation limited to the restricted cardiac field-of-view provided in the initial reconstruction.

"The jury is still out on that one," White said.

The study provides an interesting catalogue of findings but still raises questions regarding the prevalence of certain conditions and how they affect clinical management, said Dr. Allen J. Taylor, chief of cardiology at the Walter Reed Army Medical Center in Washington, DC.

Routine CTA post-bypass surgery, on the other hand, has not been proposed as the standard indication. More clinical trials, however, could answer these questions, he said.