CTA screening study shows soft-plaque risk in police

New Jersey police officers were expected to have high levels of coronary artery plaque at coronary CT angiography (CTA), according to researchers from Atlantic Medical Imaging in Galloway, NJ. The unexpected finding was that more than a third of those with coronary artery plaque had no calcified plaque whatsoever.

The study shines a patrol-car spotlight on an occupation considered to be at higher risk of coronary artery disease (CAD) -- not specifically because of advancing age or diet, but likely due to occupational stress.

David Dowe, MD, and colleagues examined 692 New Jersey state police officers in a rare screening study of asymptomatic individuals in law enforcement. The officers were invited in for coronary CTA scans free of charge, Dowe told AuntMinnie.com in an interview.

"We wanted to see what screening coronary CT angiography would do, but we didn't want to do it with just anybody, and screening the general population just didn't seem all that ethical," Dowe said. "So we decided to perform the screening study on policemen and firefighters."

Dowe presented the research at the 2010 Society of Cardiovascular Computed Tomography (SCCT) meeting in July.

All participants were 25 years of age or older, and they were asymptomatic or had symptoms possibly related to coronary artery disease but were self-treating. Patients were considered for the study regardless of the presence of CAD risk factors, Dowe explained.

The researchers excluded anyone being evaluated for symptoms possibly related to coronary artery disease, or who had been scanned with coronary CTA but whose images were missing any vessel segment.

The results were expressed in the following groups, according to Dowe:

  • Normal: No plaque
  • Mild: Plaque with the greatest stenosis being < 50% of the lumen diameter
  • Moderate: Plaque with the greatest stenosis being between 50% and 70% of the vessel diameter
  • Severe: Plaque with the greatest stenosis being > 70% of the vessel diameter

The patient cohort turned out to be surprisingly high-risk, especially considering the low mean body mass index (BMI) of just 31, Dowe said. Of the 374 normal patients in the study, fully 237 (65%) were dyslipidemic. And considering that screening of asymptomatic patients with CTA is by no means standard procedure, the yield was extraordinarily high.

"Of 692 patients -- a fairly sizeable number -- we came up with 19 [2.7%] who had moderate or severe disease," including 16 with moderate disease and three classified as severe, Dowe said. "We call mammography successful if it picks up five cancers per 1,200 patients, which is 0.5% to 1%, so this study detected a lot of people with significant disease."

Nine of the 19 patients deemed to have significant disease went on to have stents implanted or coronary artery bypass graft (CABG) surgery. The nine patients are all doing fine, he said, and there was a 10th asymptomatic patient in his 30s who had normal coronary arteries but a 5.5-cm ascending aortic aneurysm that was also treated.

Calcium-free disease risk

What surprised the researchers were the high rates of noncalcified plaque.

"We found that of patients with plaque excluding the normals, a large number of them presented with purely noncalcified plaque," Dowe said. Of 692 patients, including 318 (47%) with any plaque, 109 (36.5%) presented with purely noncalcified plaque. These patients would have been missed using coronary artery calcium scoring only, Dowe said.

Mild Moderate Severe
No. of patients with any plaque 299 16 3
No. of patients with noncalcified plaque 107 (36%) 0 2 (66%)
More than a third (26%) of patients with coronary artery plaque had no calcifications.

"This does raise a serious question as to whether we're leaving too much info on the table just looking at calcium scores," Dowe said.

"If you have a calcium score of zero, you have a 0.4% risk of acute coronary syndrome over the next five years," he said, "which is fine and dandy, but I think when you're detecting patients with no calcified plaque, you're getting them earlier because they haven't formed calcium yet, and it raises the question of what is the prognostic significance of finding these patients with noncalcified plaque."

A few studies have sought to quantify this risk. For example, Min and colleagues from Weill Cornell Medical College in New York City found that patients with noncalcified plaque had a 3.39 times higher risk of mortality than patients with no coronary artery plaque, Dowe said.

The lack of treatment among at-risk individuals was another salient finding. But however effective the use of statins might be in lowering the risk of cardiac events, most people aren't using them, Dowe said.

Of the 374 normal patients, 237 (65%) were dyslipidemic, and 43 of these 237 (18%) were on statins prior to coronary CTA but had no plaque. Of the 299 patients with mild disease, 230 (77%) were dyslipidemic but just 66 (29%) of the 230 were on statins.

Of the 16 patients with moderate disease, 13 (81%) were dyslipidemic yet only eight (62%) of the 13 were on statins. Among the three patients with severe plaque burden, one (33%) was dyslipidemic, and this patient was not on statins.

"I think there's value in finding these patients earlier, getting the right patients on statins, and preventing the heart attack 10 to 20 years from now," Dowe said.

The results show that coronary CTA can help detect and potentially contribute to better management of dyslipidemic patients in high-risk occupations who are asymptomatic or symptomatic and self-treated, Dowe said.

"My greatest save was a 39-year-old police officer with three children under 6 who was having chest pain but passed a stress test," Dowe said. "He was being treated with Rolaids and he had a critical stenosis of the proximal [left anterior descending artery] with a plaque ulceration."

By Eric Barnes
AuntMinnie.com staff writer
October 4, 2010

Related Reading

Accurate, fast soft-plaque measurement seen with coronary CTA, September 21, 2010

Advanced CT may have role in noncalcified plaque assessment, September 8, 2010

SHAPE II task force revising cardiac risk guidelines, August 17, 2010

Coronary calcium usually ignored on chest CT, August 12, 2010

CT equivalent to IVUS for culprit plaque detection, December 4, 2008

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