"We have a technology with no evidence of benefit; we have a technology with real concern for harm," Lauer said. "What are we doing? The time has come for the leadership of the cardiovascular community to have the courage to stop this and to change the paradigm by which imaging technologies are promoted."

Dr Julie M Miller

Lauer made his appeal as the discussant for Coronary Evaluation Using Multislice Spiral CTA Using 64 Detectors (CORE 64) trial, presented seconds earlier by Dr Julie M Miller (Johns Hopkins University, Baltimore, MD). The multicenter trial results suggested that 64-slice CT has comparable diagnostic accuracy to quantitative coronary angiography in patients without highly calcified vessels and suspected coronary artery disease (CAD).

Lauer, however, decried CORE 64 for not meeting "core" criteria for a well-designed clinical trial, a fault of other CT studies as well, he suggested. Indeed, the "deeper message" of including a CTA study as part of the late-breaking clinical-trials plenary might not just be that it is the "latest hot topic" in cardiovascular imaging, but rather "the recognition that imaging should be subjected to the same rigorous clinical-trial evaluation as other cardiovascular procedures and strategies," he suggested.

The time has come for the leadership of the cardiovascular community to have the courage to stop this and to change the paradigm by which imaging technologies are promoted.

In his discussion of the results, however, Lauer dismissed the trial as typical of all that is wrong with many modern-day imaging studies. CORE 64, he argues, did not enroll a representative patient population, but rather a group of patients already referred for coronary angiography.

"This is a group of patients that is fundamentally different from the patients to whom this hot technology is being applied," he said. Moreover, "There was no comparison, no control group, no meaningful follow-up, and no assessment of hard cardiac events."

With conspicuous exceptions—including early large-scale, long-term trials showing that mammography screening prevents breast-cancer deaths and the MASS study of ultrasonography for abdominal aortic aneurysm screening—recent imaging studies have not had to demonstrate that the test has an impact on patient outcomes, Lauer argues.

"When doctors refer patients for mammography, they are saving lives," he said. "Ultrasound of the abdominal aorta is a life-saving imaging test. As physicians, we should be guided by the principle primum non nocere: first, do no harm. In the case of CTA, there is cause for concern of harm."

Citing data showing the lifetime risk of cancer due to a single CTA scan, Lauer suggested the actual risk might be much higher, given the temptation to order multiple CTA tests. "By letting this technology loose upon the public we may be causing thousands of preventable cancers," he said.

He continued: "We know nothing about the diagnostic accuracy of CT angiography in the real word, we have minimal data on its prognostic value, but most important, we have no evidence, none at all, that the use of CTA saves lives or prevents heart attacks. As physicians, our primary responsibility must be to patients and to the public health. We must seek to maximize value while minimizing harm. CTA is a technology with enormous promise. It may save lives, but before we get carried away, we have to prove it."

Speaking with heartwire after the plenary session, Miller acknowledged that she'd been somewhat blindsided by Lauer's comments, adding that she felt his criticisms were directed more at CT in general than at her study in particular. "What we tested was not what he was speaking about. He was concerned about the mass application of CT to people who are asymptomatic, and we don't want to do that, that's not what we proposed, and that's not what we tested. We tested whether this technology can work in symptomatic patients with possible CAD, and that's what we showed."

Dr Armin Arbab-Zadeh

She points out that roughly 1.2 million cardiac catheterizations are performed in the US each year, with 20% to 30% of the results showing no signs of cardiovascular disease. "That means 200 to 300 thousand people are exposed to unnecessary procedures. These are very expensive, and the complication rate is 1% to 2%. If you add that up, you could eliminate all those potentially serious complications."

Likewise, study coauthor Dr Armin Arbab-Zadeh (Johns Hopkins University) pointed out to heartwire that CORE 64 was a necessary step toward the type of trials Lauer is calling for.

"We are well aware that we need more outcome studies for multislice CT; on the other hand, these studies are in progress, and they take several years and many patients to be completed," he said. "In the meantime, I believe we should use CT judiciously, but I think it's ridiculous to call for a moratorium. The available data suggest you can omit cardiac catheterization in many patients because CTA can rule out CAD reliably."

I believe we should use CT judiciously, but I think it's ridiculous to call for a moratorium.

In the case of the CORE 64 cohort, these were patients who one way or another were going to be exposed to radiation during their diagnostic test, Arbab-Zadeh observed. If CTA can replace conventional coronary angiography, patients will at least be spared an invasive procedure.

But Arbab-Zadeh also acknowledged that emerging evidence suggests the most likely role for CTA might be in patients with low to intermediate risk of CAD, a group that would not be one a one-way street to the cath lab. However, he points out that any new test needs first to be validated against the gold standard, conventional coronary angiography.

"It's hard to do invasive procedures for validating your findings in people at low to intermediate risk; it's just not ethical," he said. "The only way to do it is with outcomes studies. I would agree we need them, but in the meantime we need to take baby steps, and I think it's unfair that he didn't acknowledge the importance of this trial. This is the first multicenter trial asserting that CTA is actually a reliable tool for detecting obstructive coronary artery disease. We need to acknowledge that this in an important step."

According to former AHA president Dr Raymond Gibbons (Mayo Clinic, Rochester, MN), CTA in the US is currently quite limited, primarily because it is not reimbursed in every state. In fact, the AHA has formally told the Centers for Medicare & Medicaid Services (CMS) that it believes there should be a national coverage policy for CTA, at least in patients for whom research has demonstrated the test to be useful.

"The AHA has a position statement on CTA, and it covers when we think it should be done and when it should not be done," Gibbons told heartwire. "We believe science should guide what we do; we have a scientific statement, and that's what we try to follow."

But Gibbons rejected the notion that the AHA should put a halt to any use of CTA until outcomes data are in. "The notion that national organizations are in a position to place a moratorium on CTA is unrealistic," he said.