CCTA Gains Ground for Low-Risk Chest Pain

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CT angiography of the left circumflex shows a stenosis less than 70 percent. (Source: Frank Rybicki, MD, Brigham and Women’s Hospital in Boston)

Triage methods for low-risk chest pain lack consensus. However, a recent scientific statement and appropriate use criteria (AUC) have recommended best practices, paying particular attention to coronary CT angiography (CCTA) as a triage tool.

Let’s get clinical

More than eight million U.S. patients with chest pain or other symptoms associated with potential coronary disease visit the emergency department (ED) annually—a majority of whom do not have coronary artery disease (CAD) or acute coronary syndromes (ACS). Low-risk patients with ACS are typically identified as those “with no hemodynamic derangements or arrhythmias, a normal or near-normal electrocardiogram (ECG), and negative initial cardiac injury markers,” according to a recent American Heart Association (AHA) scientific statement (Circulation 2010;122:756-776).

“Those patients who present to the ED with no instability of hemodynamics or rhythm, negative CK-MB and a normal ECG, but have chest discomfort are automatically classified as low risk for a coronary event,” explains Ezra A. Amsterdam, MD, professor of medicine in the division of cardiovascular medicine at the University of California, Davis Health System in Sacramento and lead author of the AHA statement.  
To further examine these patients, clinicians can employ various tests, such as an exercise treadmill exam, a stress echo, SPECT imaging or a CCTA scan. Due to the attention paid to excessive imaging over the past few years, some are advocating a return to more basic assessments.

“It has been demonstrated that among patients presenting to the ED with chest pain, those with less than 5 percent probability of MI can be identified from the presenting symptoms, past history and ECG,” according to the statement. “[A]lthough the cause of chest pain in these patients is frequently elusive, basic clinical tools provide powerful estimates of cardiac risk.”

However, the authors state that non-invasive imaging, such as CCTA, could have a role. “[U]nlike exercise treadmill testing, SPECT myocardial perfusion imaging and stress echo, CCTA provides anatomic rather than functional information regarding coronary patency by producing a noninvasive coronary angiogram.”

Joseph A. Ladapo, MD, PhD, from the department of ambulatory care and prevention at Harvard Medical School in Boston, agrees. “While CCTA has limitations with localizing vulnerable plaque, the test can identify patients who are vulnerable for CAD via their atherosclerotic burden through the calcification of the coronary arteries. CCTA can help identify those patients who require further treatment.”  

The statement highlights several potential limitations of CCTA, including suboptimal coronary artery visualization caused by extensive calcium, and radiation exposure. However, it cites a recent study that reported new methodology that could reduce radiation dose by 50 percent, but this finding needs further validation.

Appropriate use criteria (AUC)

Amsterdam notes that each practicing clinician has his or her test preference. “Clinicians bring different perspectives into practice, which they apply in the best interests of their patients,” he says. However, new multi-society AUC could make the choice of when to intervene with CCTA as a triage tool less subjective (J Am Coll Cardiol 2010;56:1864-1894).

In the criteria, CCTA is deemed appropriate for patients with chest pain whose preliminary tests suggest low or intermediate pre-test probability for CAD, because CCTA helps exclude the presence of CAD with time sensitivity, says the criteria’s lead author Allen J. Taylor, MD, co-director of non-invasive imaging at Washington Hospital Center, Washington, D.C.  

“There is a real dearth of information about the effectiveness of imaging, especially in relation to improved patient outcomes because these diagnostic tests are only a part of the spectrum of patient care and not the only driver of outcomes,” Taylor says.

As a result, the AUC authors hope that the updated criteria will better inform decision making: “Facilities and payors may choose to use these criteria either prospectively in the design of protocols and preauthorization procedures, or retrospectively for quality reports. … It is hoped that payors would use these criteria as the basis for the development of rational payment management strategies.”