Bethesda, MD - The American College of Cardiology (ACC), in collaboration with a host of other professional societies, has released new appropriateness criteria to help guide usage of cardiac computed tomography (CT) and magnetic resonance (MR) imaging for diagnosis and management of cardiovascular disease [1].

The document, which appears on the ACC website, comes amid mounting interest in and confusion over the role of fast-evolving imaging modalities in cardiovascular medicine. No official guidelines on the use of either modality for cardiac applications have been released for at least six years, and the authors of the new document are quick to point out that this document doesn't take their place.

"These are not guidelines," Dr Allen Taylor (Walter Reed Army Medical Center, Washington, DC), a member of the panel, told heartwire. "It's a very different animal and has a different use. Guidelines are published when the evidence base is robust enough to come out with very clear categorical statements. That database is in development. That's why appropriateness criteria are an intermediate step. They mix clinical judgment with available data."

Appropriateness criteria are a relatively new venture for the ACC, which partners with different specialty organizations depending on the focus. The CT and MR document represents the second and third set of appropriateness criteria (combined); last October the ACC, in collaboration with the American Society of Nuclear Cardiology, issued appropriateness criteria for single photon emission computed tomography myocardial perfusion imaging. The documents are designed to blend scientific evidence with practice and, as Taylor pointed out, are something that will be of interest primarily to physicians wanting to know what procedures are appropriate to perform and for payers wanting to know what procedures could be appropriately reimbursed.

Lead author for the writing group was Dr Robert C Hendel (Midwest Heart Specialists, Fox River Grove, IL). He explained to heartwire, "Appropriateness criteria tell you it is reasonable to perform this test in a specific clinical scenario, and then we outline the specific clinical scenario."

The paper focuses on 39 CT and 33 MR indications identified by the panel as encompassing the majority of cases referred for each of the modalities. Each indication was then ranked for appropriateness by the 15-member technical panel out of a score of 9: a score of 1-3 indicated that a test for the application in question would be "inappropriate"; 4-6, that the value of a test was "uncertain"; and 7-9, that a test was "appropriate."

In all, 13 of the 39 CT indications were deemed appropriate, 12 uncertain, and 14 inappropriate. Examples of highest-scoring indications included evaluation of intra- and extracardiac structures using cardiac CT or, in the case of suspected coronary anomalies, CT angiography. Lowest-scoring indications, given an "inappropriate" ranking, included evaluation of patients with a high pretest probability of CAD based on risk factors or results of other tests.

For MR, 17 of 33 indications were ranked as appropriate, seven as uncertain, and nine as inappropriate. Highest-scoring indications included assessment of suspected coronary anomalies (using MR coronary angiography) and evaluation of ventricular and valvular function (using LV/RV mass and volumes, MR angiography, quantification of valvular disease, and delayed contrast enhancement). Indications deemed "inappropriate" included detection of symptomatic CAD using MR, MR coronary angiography, perfusion, or dobutamine stress function MR.

The category of "uncertain" is one of the most interesting, Hendel points out, and where the writing group expects to see the most change in the appropriateness criteria in successive editions: the aim of the ACC is to rerelease appropriateness criteria every 18 months.

"CT and MR are such dynamic and evolving areas that we expect things to change monthly," Hendel said. "So some of the categorizations may already be in question, particularly in the category of 'uncertain,' and that just meant that the panelists either strongly disagreed on their interpretation of what was appropriate or inappropriate or more likely there's just such limited information that the only thing they could say is that they need more data, more research, more conclusions. And that's another of the messages from the appropriateness criteria: it identifies those indications where we need more information and we have to do more work."

Importantly, scores were derived from median results, and disagreement inevitably occurred for different indications, just as physicians using the document may not always concur with every ranking. "I'm sure some people will disagree with some of this, because that's the nature of opinion, and across the panel there were a range of scores given," Taylor said. "Everyone has personal beliefs and practice patterns, but that's why you put together a panel."

In this case, the technical panel was made up of imaging specialists within the CT and MR communities, cardiologists, radiologists, referring physicians, health-service researchers, and a medical director from a private payer.

The criteria do not actually compare CT with MR or either modality with other tests, including standard angiography, echocardiography, and nuclear or stress testing. "That's a very important issue," Hendel conceded. "The concept is called an efficiency analysis, and the ACC is planning on convening panels for specific indications and going through the entire gamut of options to try to define which tests among those can be considered reasonable. We want to be fair and clear to all modalities. We're not looking to say what is the one best methodology that you and everyone else should use, because there is variability in how they're performed. On the other hand, we will address this issue in an efficiency analysis to come up with, for example, if you have a diabetic with chest pain it would be appropriate to do the following two tests, but it would be inappropriate to do this other test."

Overall, says Taylor, the document should prove "helpful" in day-to-day practice. "People want to render appropriate care, and it provides some expert opinions as to what is appropriate at the current time; people also don't want to render inappropriate care, and hopefully they will heed the 'inappropriate' criteria, staying away from certain indications."

Hendel agrees. "I think the appropriateness criteria are well-supported in the literature, and they're consistent with other types of guidelines. I think that most practitioners are going to find them to be what they're already doing in practice—I hope—and in some cases they're going to be a little surprised and say, well, I better reexamine what I'm doing here because that doesn't seem like it's the best use."

As for formal guidelines, an American Heart Association statement on cardiac CT and an ACC document on calcium screening are still expected to be out within the next six months. The American College of Radiology, the Society of Cardiovascular Computed Tomography, the Society for Cardiovascular Magnetic Resonance, the American Society of Nuclear Cardiology, the North American Society for Cardiac Imaging, the Society for Cardiovascular Angiography and Interventions, and the Society of Interventional Radiology were coparticipants in the development of the CT and MR appropriateness criteria.