SNOWMASS, COLO. — CT angiography has rapidly emerged as the most cost-effective imaging technique to exclude acute coronary syndrome in the emergency department.
The overall diagnostic accuracy of CT angiography (CTA) is essentially equivalent to that of SPECT myocardial perfusion imaging, its main competition. But CTA is the clear winner in terms of time to diagnosis and cost, Dr. Christopher M. Kramer said at a conference sponsored by the American College of Cardiology.
Chest pain accounts for more than 6 million ED visits annually, resulting in 1.24 million admissions for unstable angina/non–ST-elevation MI and another 330,000 for STEMI. Emergency physicians are eager for new ways to rapidly and reliably rule out acute coronary syndrome—and CTA has a lot to offer in this regard, said Dr. Kramer, professor of medicine and radiology and director of the cardiovascular imaging center at the University of Virginia, Charlottesville.
In the recent 16-center CT-STAT trial, now in press, 701 low-risk patients with chest pain and a nondiagnostic ECG in the ED were randomized to CTA or the hospital's standard protocol, which typically included serial biomarkers along with SPECT myocardial perfusion imaging (MPI).
Time to diagnosis averaged 6.3 hours in the group who received the standard work-up compared to 2.9 hours with CTA, a 53% reduction. Median costs to obtain a diagnosis were $3,158 with the standard protocol and $2,137 with CTA, a 38% reduction.
ACS was diagnosed in roughly 3% of patients in each study arm, and invasive coronary angiography was performed in 5%. No significant stenosis was found in 82% of patients who underwent CTA and 90% who had MPI.
The 6-month major adverse cardiac event rates in this low-risk CT-STAT population were 0.3% in the standard management group and 0.0% in the CTA arm.
SPECT MPI is at present slightly more widely available in EDs around the country than is CTA. The other two up and coming imaging methods with utility in the setting of chest pain and nondiagnostic ECG in the ED—cardiac MRI and contrast echocardiography perfusion—have only limited availability. In terms of accuracy, they're similar to MPI and CTA, said Dr. Kramer.
A recent pooled analysis of MPI in ED evaluation of chest pain that included nine studies and nearly 1,900 patients showed the imaging method had 98% sensitivity and 73% specificity for identifying acute coronary syndrome. On the basis of its ability to reduce hospital admissions, it has been estimated that MPI reduces hospital costs by about $800 per patient.
Dr. Kramer serves as a consultant to Siemens Medical Solutions and is the recipient of research grants from Astellas and GlaxoSmithKline.
CTA is the clear winner in terms of time to diagnosis and cost in the emergency department.
Source Dr. Kramer