Circ Feature: CCTA correlates with cath angio findings of plaque disruption
Calcified and noncalcified plaque by CCTA. Source: Fabian Bamberg, MD, University of Munich
In a highly selected group of patients with acute unstable or new-onset angina, coronary CT angiography (CCTA) was able to delineate features of plaque disruption, including ulceration and intraplaque dye penetration, which are specific markers of invasively identified complex plaque, according to a single-center study published in the March 16 Circulation: Cardiovascular Imaging.

"This extends the work we've been doing regarding CCTA and plaque," senior author James A. Goldstein, MD, from William Beaumont Hospital in Royal Oak, Mich., said in an interview. "Using CCTA, we are able to identify those patients and plaques that are at greatest risk of causing events."

Led by Ryan D. Madder, MD, the Beaumont researchers evaluated 60 patients with quantitative CCTA for plaque stenosis, volume, remodeling index and volume of low-attenuation plaque. Researchers also evaluated plaques with more than 25 percent stenosis for features of disruption, including ulceration and intraplaque dye penetration. They compared CCTA results with catheter angiography.

Researchers identified 294 plaques by CCTA, of which 37 percent had features of disruption, including ulceration in 18 percent and intraplaque dye penetration in 27 percent.

When compared with nondisrupted lesions, Madder and colleagues found that plaques with ulceration or intraplaque dye penetration by CCTA were more voluminous, more often positively remodeled, contained more low-attenuation plaque and were more often found to be complex by catheter angiography. All findings were significant.

The sensitivity of CCTA to demonstrate features of disruption was 53 to 81 percent, while the specificity was 82 to 95 percent.

"This is the largest study of its kind to compare CCTA and catheter angiography in patients with symptoms of chest pain and unknown etiology," Goldstein said.

When the plaques were proven by catheter angiography to have features of instability, the researchers then looked at the CCTA images to see if they could have determined the same noninvasively.

"It's important to demonstrate that CCTA has the capability to detect stenosis and the severity of the narrowing, but it's equally important to be able to demonstrate whether those plaques have become unstable," Goldstein said.

Atherosclerosis is chronic and grows slowly, but is often punctuated by flares and erosion. Plaques then become unstable, clots can form and break off and cause angina or death.

It's well established that x-ray dye can penetrate into ulcerated, unstable plaques. These are the lesions that pose the greatest risk to patients. If CCTA can identify these plaques early before the patients have catastrophic events, patients could then be treated either with stenting or more aggressive medical therapy, Goldstein said.

"These unstable lesions are the precursors to vulnerable lesions, those which are about to rupture. CCTA could potentially be used as a method tool to identify unstable plaques," he said.

"A critical step in the process of plaque instability is disruption of the protective fibrous cap, which once breached results in intracoronary thrombus formation," study authors wrote. "Plaque rupture is evident by invasive angiography as a 'complex' lesion, characterized by luminal irregularity, ulceration, haziness and intraplaque contrast penetration."

In addition, by direct imaging with intravascular ultrasound (IVUS), "unstable plaques are bulky, positively remodeled, have low-attenuation and show signs of disruption, including ulceration and luminal clot."

Goldstein and colleagues demonstrated that in addition to characterizing features of vulnerable plaques, CCTA can identify features of plaque disruption among individuals with high CT image quality.

"This proof-of-concept study showed that CCTA has the ability to identify plaques that are disrupted," Goldstein said. "These plaques are at the most extreme end of stability and patients with such plaques might benefit from earlier treatment."