When to Do a Coronary CTA: Defining Appropriate Use

Abbott Northwestern Hospital in Minneapolis, Minn., performs 12 to 17 coronary CTAs daily with its Siemens Medical Solutions Somatom Definition dual source CT scanner.

Cardiac care is on the upswing in 2007. Aging baby boomers, advancing medical technology, more educated physicians and public awareness are driving an unprecedented growth in the diagnosis and treatment of heart disease. One of the fastest growing diagnostic procedures is the coronary computed tomography angiogram (coronary CTA) using a 64-slice CT scanner. The explosion in coronary CTA has created a need to educate cardiologists, radiologists and internists on its appropriateness of use—who, what, when, where, and why.

More and more physicians are becoming aware of the benefits of coronary CTA thanks to immense growth of 64-slice CT imaging. The benefits include speed, very low risk, and an amazing amount of information, says Tony DeFrance, MD, a board-certified interventional cardiologist and medical director of CVCTA Education Center in San Francisco. “In just 10 seconds, we can get an entire roadmap of the arteries,” DeFrance says. “We can see into the walls of the blood vessels and see the earliest stages of coronary artery disease, so we can detect it even long before an invasive angiogram.” 

The procedure offers a less-expensive, noninvasive alternative to cardiac catherization. There has been tremendous growth in the use of CTA, especially in the emergency room setting and outpatient imaging facilities. The growth is creating a huge need and demand for training in this area, says DeFrance, who each week spends most of his time teaching nearly 100 physicians onsite and across the country. But his eyes are busy reading images, too. At CVCTA, he oversees eight to 12 coronary CTAs that are performed daily on the facility’s Toshiba America Medical Systems’ Aquilion 64. 

DeFrance’s outreach is part of a national effort to educate practitioners, with the support of various cardiology organizations, healthcare facilities and systems and medical technology vendors.


Guidelines offer a beginning

On a national level, help in determining the appropriate use of CCTA comes in the way of guidelines published in 2006. Last November, the American College of Cardiology Foundation (ACCF) along with the Society of Cardiovascular Computed Tomography (SCCT) and other key groups released “Appropriateness Criteria for Cardiac Computed Tomography and Cardiac Magnetic Resonance Imaging.” While not meant to be a federal standard, it provides a general basis of knowledge and direction.

“Developing appropriateness criteria and best practice guidelines for coronary CTA is essential. We need this technology adopted and incorporated in a way that benefits the patient and uses the best available evidence,” says DeFrance, who is a founding member of SCCT.

John Lesser, MD, FACC, an SCCT board member says, “Appropriateness guidelines are very important. They are developed based on the combination of literature and diverse expert opinion…and are designed to be frequently updated.” Lesser is a cardiologist at Abbott Northwestern Hospital in Minneapolis, Minn., where in January they installed a Siemens Medical Solutions Somatom Definition dual source CT scanner. Abbott Northwestern performed 5,000 cath lab procedures last year, and currently performs 12 to 17 coronary CTAs daily.

“Guidelines allow payors and physicians who do not have extensive experience in the technique to have confidence and knowledge about whether the technology is being used responsibly,” Lesser says.

Some insurance companies turn to the guidelines to determine payment for the procedure, which on average costs $1,200. Others, such as California Medicare, have drafted their own criteria to determine payment for the procedure. DeFrance says CVCTA follows “Medicare guidelines for California in terms of coverage indications. Most of these overlap with the appropriateness document.”


Good, old-fashioned judgment

But the guidelines are not designed to replace good, experienced physician judgment about which cardiac patients should undergo CTA. “I think it’s very difficult with these cardiac patients to strictly adhere to guidelines because there are so many variables from patient to patient,” says Radiologist James P. Earls, MD, vice president and medical director of Fairfax Radiological Consultants (FRC) in Fairfax, Va., who is director of FRC’s cardiac CT program, and co-director of the cardiac CT program at Inova Heart and Vascular Institute at Inova Fairfax Hospital in Falls Church, Va.

“I think we have to rely on the referring physician’s clinical judgment as to whether this is an appropriate pre-test,” says Earls, whose experience comes from doing 8,000 coronary CT studies.

At Fairfax, there are four GE LightSpeed VCT 64-slice scanners installed, including one that was recently upgraded to XT. This year, Earls expects a 60 percent increase in coronary CTA imaging procedures. He attributes the growth to an “increased awareness across the board by all referring physicians, cardiologists and internists. The number of scientific studies supporting the accuracy, use and cost-effectiveness of coronary CTA is growing rapidly, and the clinicians are not getting educated on the appropriate use of this technology. Much growth also is patient-driven—they’re aware of it from what they’ve seen in the media.”

Earls teaches “Advanced Cardiac CTA,” a three-day course sponsored by GE. The course, targeted for radiologists and cardiologists, is held at FRC and focuses on learning how to perform and interpret coronary CTA examinations. Participants typically process and interpret 30 to 35 live cases and 40 to 45 archived cases during the course.

For CTA studies, Earls says at FRC they see about 10 uses that are commonly performed in patients with known or suspected coronary disease. On the Fairfax web site, www.fairfaxradiology.com, a list of suggested criteria, “Current Clinical Indications for Coronary CTA,” closely aligns with the appropriate use guideline. The site also provides educational information on coronary CTA with photos and a Q&A.


Passing the baton of knowledge

William Guy Weigold, MD, a member of the technical panel, like DeFrance, Lesser and Earls, spends a good amount of his time sharing his knowledge on the appropriate of use for CTA, mostly at conferences and seminars across the country. Weigold is director, Cardiac CT, Division of Cardiovasular Disease, at Washington Hospital Center in Washington, D.C., where they use a Philips Medical Systems Brilliance 64 CT scanner.

At Washington Hospital Center, where its busy cath labs perform 20,000 cath procedures a year, training is important. Weigold says, “I think what’s critical for every institution that [performs coronary CTA procedures] is to have the staff and personnel properly trained, to make sure that the patient preparation and nitty-gritty details of the actual acquisition are all attended to carefully and properly so that good date acquisition occurs.”


Best case scenario

Coronary CTA is most useful as a tool “to exclude obstructive CAD in patients with chest pain; and to quantitate coronary calcification in asymptomatic patients at-risk for heart attack,” says Weigold.

Lesser notes cardiac care has changed with CTA by identifying a whole group of people who were thought not to have CAD. “These are the patients who underwent a nuclear stress perfusion study or an echo and were told there is no evidence of disease. Yet, in a large group of these people, we do a CT and sometimes find very extensive coronary disease, but sometimes not necessarily significant coronary stenosis.”

“The quality of the scan is a very important factor in the accuracy of the test. The ways in which the scans are being done also are of critical importance. Coronary CTA is something that needs to be done properly for it to work well. That means patient selection and then actually doing the scan itself,” he adds. 

As an example of good patient selection, Weigold sites this case: “A 45-year-old man with a history of hypertension and hypercholesterolemia, presenting to the physician’s office with a 2 to 3 week history of recurring chest discomfort, variably related to exercise or exertion (such as atypical chest pain that is clearly due to coronary obstruction). In this case, especially, coronary CTA can detect the presence of any coronary atherosclerosis with extremely high sensitivity; and determine whether or not obstructive coronary disease [producing symptoms] is present.”


Not always appropriate

Sometimes a coronary CTA is ordered when it might not be necessary or would not be useful. “The most inappropriate use is in patients with a combination of factors that compromise the scan accuracy [combination of a calcium score >1500; elevated heart rate; obesity; atrial fibrillation; and inability to hold still or breath hold],” says Lesser.

Lesser has been known to cancel a case that should not be performed, and says, “If we believe that the scan will not be worth the patient exposure to contrast or radiation, we may cancel the scan or expedite an alternative test to help answer the clinical problem.” He adds that in these cases, they contact the ordering physician to discuss the matter.

DeFrance also has seen these cases. “We have many referrals of asymptomatic patients with risk for heart disease which is not currently an appropriate guideline.” 


Pluses and minuses

But coronary CTA is not without its limitations. The technology “requires heart rate modulation, which can usually be achieved with beta-blockade, but sometimes images quality is limited by cardiac artifact,” Weigold says. “Dense coronary calcification obscures visualization of the coronary lumen; artial fibrillation is generally a relative contradiction to coronary CTA, although research and improvements may change this in the future.”

DeFrance says that even with criteria, it is still difficult to get insurance companies to pay for the CTA studies.

On the plus side of limitations and challenges, the advancement of technology has provided more information and possibilities for diagnosis than ever before. Even the appropriateness of use criteria addresses it in the introduction. “Rapid technological advances and new clinical applications in cardiovascular imaging technology, coupled with increasing therapeutic options for cardiovascular disease, have led to explosive growth in cardiovascular imaging.”

Keeping up with the advances will take collaboration from all those involved—radiologists, cardiologists, referring physicians, other clinicians, patients, healthcare organizations, and vendors.