Marlene Busko

July 18, 2014

SAN DIEGO, CA — Among patients who have acute chest pain but have a negative initial ECG or troponin test in the emergency room, a coronary computed-tomography CT angiography (CCTA) scan that detects high-risk plaque features can identify those at higher risk of imminent ACS, researchers report[1].

Moreover, the increased risk of ACS (MI or unstable angina) associated with high-risk plaque is independent of the increased risk from having significant stenosis or multiple other CVD risk factors.

Dr Maros Ferencik (Massachusetts General Hospital and Harvard Medical School, Boston, MA) presented these findings from a study based on data from the Rule Out Myocardial Infarction With Computer Assisted Tomography II (ROMICAT II) trial, here at the Society of Cardiovascular Computed Tomography 2014 Annual Scientific Meeting .

"An assessment of plaques is feasible in clinical practice and relatively easy to perform," he said.

The abstract, which was judged to be one of the top five abstracts at the meeting, confirms smaller, single-center studies, session moderator Dr Damini Dey (Cedars Sinai Medical Center, Los Angeles, CA) told heartwire .

"The take-away message is that beyond stenosis assessment, assessment of high-risk plaque features is important, so that at-risk patients can be identified before [having a] heart attack." Currently, high-risk plaque features are not reported clinically, she noted, but "this is something that an experienced doctor—who reads the CTA—can add quite easily to reporting."

Study Spots Dangerous Plaque

Traditionally, CCTA evaluation of patients with acute chest pain has focused on detecting the presence of coronary stenosis and coronary plaque, Ferencik noted. An absence of coronary plaque suggests a low likelihood of ACS. An absence of coronary stenosis, however, does not reliably rule out future cardiac events, since up to 25% of patients who have no significant stenosis by CTA still have ACS. Moreover, having significant stenosis is only a moderate predictor of having ACS, Ferencik noted.

"So there are chances for improvement," he said.

Identifying the presence of plaque with foreboding features might help identify high-risk patients. Other CCTA studies have shown that patients with ACS are more likely to have poor outcomes if they have plaques with napkin-ring sign, positive remodeling, spotty calcification, and low-density plaque area (<30 Hounsfield units).

The researchers aimed to determine whether high-risk plaque detected by CCTA would improve the ability to diagnose ACS in patients who present to the ER with acute chest pain without objective evidence of myocardial ischemia.

They analyzed data from 472 patients in the CCTA arm of ROMICAT II. The patients had a mean age of 53.9 years, and 52.8% were men.

Three experienced readers assessed the CCTA images to determine the presence of nonobstructive CAD, obstructive CAD (>50% stenosis), and high-risk plaque features.

Using regression analysis, the researchers determined the association of high-risk plaque with ACS during the index hospitalization and whether this was independent of significant CAD and CVD risk factors such as older age, male gender, hypertension, hyperlipidemia, diabetes mellitus, smoking, and family history of premature CAD.

A total of 37 patients (7.8%) had an ACS during the index hospitalization; five patients had an MI and 32 patients had unstable angina.

About half of the patients (55.5%) had CAD, of which only 9.5% had obstructive CAD.

Patients with high-risk plaques were significantly more likely to have an ACS during the index hospitalization, even after adjustment for stenosis and number of cardiovascular risk factors.

Another Study Quantifies Plaque Burden

Another abstract presented at the meeting, coauthored by Dey, described a study in which the researchers used automated software to quantify plaque features in 56 lesions, which improved the ability to predict lesion-specific ischemia[2].

The abstract, which was presented at the meeting by Dr Mariana Diaz-Zamudio (Cedars Sinai Medical Center) was judged to be one of the top five abstracts by young investigators.

"Automated measurement of plaque characteristics . . . can potentially be used as a tool to noninvasively distinguish hemodynamically significant lesions," Dey said.

Ferencik and Diaz-Zamudio had no disclosures. Dey's institution (Cedars-Sinai Medical Center, Los Angeles, CA) may receive royalties for the licensing of software used in the quantitative assessment of coronary plaque.

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