ASNC: CTA-First Strategy Increases Radiation and Contrast Exposure

September 13, 2007

SAN DIEGO -- High radiation and contrast exposure with CT angiography (CTA) call into question the escalating use of the technology as an alternative to conventional coronary angiography, investigators concluded.

SAN DIEGO, Sept. 13 -- High radiation and contrast exposure with CT angiography (CTA) call into question the escalating use of the technology as an alternative to conventional coronary angiography, investigators concluded here.

Using CTA as the first step in evaluating suspected coronary artery disease would almost triple the radiation exposure in patients with confirmed coronary artery disease compared with conventional angiography as the initial approach, Prashant Baliga, M.D., of Wayne State University in Detroit reported at the American Society of Nuclear Cardiology meeting.

Patient exposure to contrast material would more than double with a CTA-first approach.

"Coronary angiography is an extremely safe and established technique," said Dr. Baliga. "Until further refinement in the technology occurs, the escalating indiscriminate utilization is CTA is questionable."

As compared with coronary angiography, CTA is a relatively new imaging modality and its use is expanding rapidly. Little is known about the relative safety of CTA, whereas four decades of experience with coronary angiography have increasingly improved the safety, said Dr. Baliga.

To compare the safety of the two coronary imaging modalities, investigators reviewed records on 527 patients who underwent coronary angiography over a two-year period. Technical results were compared with those of a hypothetical strategy wherein the same patients would have had CTA as the initial coronary evaluation.

"Given the high negative predictive value of CTA, patients with normal coronary arteries would not have undergone any further testing, and CTA would have served as the final diagnostic step," Dr. Baliga explained. "Consistent with current practice, patients with abnormal CTA would have undergone coronary angiography to evaluate the coronary anatomy."

With coronary angiography as the initial test, the 527 patients were exposed to an average radiation dose of 7.5 mSv and a mean contrast dose of 75 mL, Dr. Baglia said.

With CTA as the initial imaging modality, patients with normal coronary arteries (N=231) would have been exposed to 11.0 mSv of radiation and 72 mL of contrast medium, he said.

Among patients with abnormal CTA results (N=296), follow-up coronary angiography would have added to the radiation and contrast exposure. Dr. Baliga and colleagues calculated that the mean radiation dose would have been 19.2 mSv and the mean contrast dose 171 mL.

Combining results of a CTA-first strategy for all 527 patients revealed a mean radiation dose of 13.6 mSv and an average contrast dose of 116 ml. Both numbers significantly exceeded those associated with coronary angiography as the initial imaging study (P