Coronary CT angiography (CCTA) could be radiology’s most notorious underperformer. As the number of CT detectors increased from one to 256 and beyond, as the resulting images showed ever more exquisite detail of the chambers and vessels of the heart, CCTA nonetheless failed to overcome politics, sluggish reimbursement, and entrenched practice patterns to achieve the acceptance so widely anticipated.
The future of that most under-appreciated of radiologic studies, however, appears destined to improve: Multiple recent studies have validated CCTA as an effective method for ruling out acute coronary-artery disease in emergency-department patients presenting with nonspecific chest pain. In addition, CCTA requires less time than a traditional work-up does, and it has a lower associated cost and radiation dose. As the most congested department of almost any hospital, the emergency department is an ideal proving ground for CCTA, which offers the rapid throughput so desperately needed to reduce patients’ waiting times and to decrease unnecessary hospital admissions.
William Shuman, MD, is professor and vice chair of the Department of Radiology at the University of Washington School of Medicine in Seattle. He says, “All emergency departments are suffering from overcongestion. They want to increase throughput and decrease turnaround time. Our research indicates that if you apply cardiac CT to the right population, it will get them in and out of the emergency department in under five hours, whereas the standard work-up can take 20 to 23 hours.”
A Population in Need
As Shuman indicates, the first issue tackled by clinicians aiming to prove cardiac CT’s worth as a triage tool is, of course, determining which group of patients will benefit most from its use. Like all diagnostic technologies, cardiac CT is hardly a one-size-fits-all method, according to Charles White, MD, professor of radiology and medicine and chief of thoracic radiology in the Department of Diagnostic Radiology at University of Maryland Medical Center in Baltimore.
In May, at the 2010 Annual Meeting of the American Roentgen Ray Society, Lu et al¹ presented the results of research evaluating 256-slice CT’s diagnostic efficacy in patients with indeterminate chest pain. White, a coauthor, notes, “Our criterion was that patients were at low to intermediate risk for acute coronary syndrome. These were not patients the emergency department was worried about, but they weren’t unworried about them, either. They would still have been stuck possibly admitting these patients unless they went and got the CT.”
White says that patients in what he calls this in-between group can be selected according to the nature of their chest pain and whether they fall into a high-risk category. “They’re patients who don’t have classic angina chest pain or classic nonangina chest pain,” he says. “The other piece is risk factors. If a 20–year-old patient presents with chest pain, it’s almost certainly not cardiac. It’s older patients, smokers, and diabetics; these are all patients who might be dealing with coronary syndrome.” White estimates that this group constitutes around 30% to 50% of patients presenting with chest pain.
Shuman et al² and May et a³ used similar criteria for research evaluating the use of 64-slice CT. Shuman (also a coauthor of the May et al study) notes that a hospital’s population at low-to-intermediate risk can vary, depending on its location and on demographic factors in its area. “Depending on the population the hospital serves, in some emergency departments, up to 20% of the patients who come in the door are presenting with chest pain,” he explains. “Patients at low-to-moderate risk for acute coronary-artery disease could represent up to 85% of that group. We use thrombolysis in myocardial infarction (TIMI) criteria to identify these patients; those with a TIMI score of four or lower, we consider at low-to-moderate risk for coronary-artery disease.”
Judd Hollander, MD, professor and clinical research director in the Department of Emergency Medicine at University of Pennsylvania in Philadelphia, has investigated the issue from the perspective of the emergency-department clinician, and the criteria for CT evaluation of chest pain used in a study by Hollander et al 4 were similar.
“We looked at patients who were admitted to the hospital, but were still on the low-to-intermediate risk scale: patients who needed some kind of testing, but we suspected the tests