Coronary CTA Effective, Efficient in Ruling Out Patients With Suspected ACS

CHICAGO, IL—Coronary computed tomographic angiography (CTA) is an effective screening tool for patients in the emergency department (ED) with suspected acute coronary syndromes (ACS), capable of safely ruling out many who would otherwise be admitted with conventional testing strategies, according to data presented March 26, 2012, at the annual American College of Cardiology/i2 Scientific Session.

The findings were simultaneously published online in the New England Journal of Medicine.

Harold Litt, MD, PhD, of the University of Pennsylvania (Philadelphia, PA), and colleagues randomized 1,370 low-to-intermediate risk patients with possible ACS in a 2 to 1 ratio to coronary CTA screening (n = 908) or traditional care (n = 462) at 5 US centers.

CTA was performed with 64-slice or greater scanning technology. At the index visit, 16% of patients who were randomized to CTA were not tested, the most common reason being elevated heart rate (27%). In patients randomized to traditional care, which was left to the discretion of the participating hospitals, over half (58%) received stress testing with or without imaging, compared with 14% of CTA patients.  In the CTA group, 83% had maximal coronary artery stenosis of less than 50%, while this rate was 77% in the traditional care group.

Accurate Assessment of Stenosis Severity

Both groups showed the same rate of cardiac catheterization (4%). In the CTA group, 76% of these patients were found to have coronary stenosis of 50% or more, while this rate was 44% in the traditional care group. Conversely, only 24% of the patients who received cardiac catheterization in the CTA group were found to have coronary stenosis less than 50%, compared to more than twice that rate among those who received cardiac catheterization in the traditional care group (56%).

Out of 640 patients with a negative CTA, none died or suffered an MI within 30 days. There were no deaths in the overall cohort, with a 1% rate of MI in each group. The revascularization rate was numerically higher in the CTA arm, but the difference was not significant (2.7% vs. 1.3%; 95% CI -4.3 to 7.0).

Cardiac CTA resulted in a higher rate of discharge from the ED compared with traditional care (50% vs. 23%; 95% CI 21.4-33.2), as well as a shorter length of stay (18 hrs vs. 25 hrs; P < 0.001) and a higher rate of patients diagnosed with CAD (9.0% vs. 3.5%; 95% CI 0-11.2).

There were no differences in 30-day resource utilization between CTA and traditional care (table 1).

Table 1. Thirty-day Resource Utilization

“Coronary CTA as the first test for low to intermediate risk patients presenting to emergency departments with potential ACS is safe and efficient,” Dr. Litt said. “We’ve shown it increases emergency department discharge rates and reduces length of stay.”

Commenting on the study, panel member Thomas C. Gerber, MD, PhD, of the Mayo Clinic (Jacksonville, FL), focused on cost and revascularization issues. “It’s clear the CTA patients went home [earlier] than the traditional care patients, but what happens in the emergency department itself is usually fairly inexpensive,” he said. “It’s not clear how many patients in each group were eventually admitted to the hospital, and it also looks like more patients in the CTA group had revascularization, which sounds expensive.”

Addressing the difference in revascularization rates, Dr. Litt noted that this reflects a more accurate CAD diagnosis. “We’re looking for the presence of coronary artery disease and significant coronary stenosis with CT,” he said, “and the fact that those patients who then went on to cath had a much higher positive cath rate shows that CT and cath are really demonstrating the same thing, and because more patients are being diagnosed with coronary disease, more patients are going to undergo revascularization.”

Better Prevention or Increased Testing?

Still, Dr. Litt added, the results do raise an important issue. “We found more patients with coronary disease with CTA vs. traditional therapy; so now patients who previously did not know they had coronary disease have coronary disease,” he said. “Will this result in better prevention for them as they go on? Will they be more likely to have lifestyle modifications, be put on statins, etc, resulting in lower future event rates and not showing up to the ED with an MI? Or will it just result in more testing? We don’t know the answer.”

Nevertheless, only 10% to 15% of patients who present with chest pain are ultimately diagnosed with ACS, while the majority are admitted to the hospital, costing over $3 billion annually, Dr. Litt and colleagues note in the NEJM paper. “Since low-to-intermediate-risk patients account for 50 to 70% of presentations with a possible acute coronary syndrome, we believe that a [coronary] CTA-based strategy can safely and efficiently redirect many patients home who would otherwise be admitted,” they write.

Sources:

Litt HI, Gatsonis C, Snyder B, et al. CT angiography for safe discharge of patients with possible acute coronary syndromes.  N Engl J Med. 2012;Epub ahead of print.

Disclosures:

• The project is funded, in part, under a grant from the Pennsylvania Department of Health; additional funding was obtained from the American College of Radiology Imaging Network.
• Dr. Litt reports receiving grant funding from Siemens Medical Solutions for unrelated CT projects.

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