Cardiac CTA hones coronary plaque assessment in patients with diabetes

Findings from a large multicenter study by U.S. researchers suggest 64-slice CT angiography is better suited to detect nonobstructive but otherwise clinically relevant coronary artery plaques in patients with diabetes than are other cardiac diagnostic tests.

Patients with diabetes are customarily classified as "at risk" for cardiovascular disease, a notion confirmed by recent data that prove diabetic patients are more prone to carry a significant coronary artery plaque burden than nondiabetic ones. However, no studies have been able to accurately predict the morbidity and mortality trends in this patient population.

Calcium scoring and nuclear stress exams can identify stenosis, but only invasive tests such as intravascular imaging can visualize vulnerable plaque. CTA has changed this and allowed cardiac imagers to realize the lack of obstructive lesions does not mean patients are free of risk for adverse coronary events, said principal investigator Dr. Fay Y. Lin, an associate professor of medicine at Cornell University.

"We may provide some reassurance to patients with a relatively low calcium score or normal stress test that may hide their true plaque burden," Lin told Diagnostic Imaging.

Lin and colleagues prospectively evaluated a cohort of 3926 patients with symptomatic cardiovascular disease, 727 of whom had diabetes. All patients underwent coronary 64-slice CTA from 2005 to 2007.

The investigators found that patients with diabetes faced nearly twice as many chances of dying from a sudden heart attack within two years of diagnosis compared with nondiabetic patients. Lin released findings at the 2009 Society of Cardiovascular Computed Tomography meeting.

Fifteen patients (2.1%) in the diabetes group and 38 (1.2%) in the nondiabetes group died during an average follow-up of two years. Patients with diabetes and coronary plaque burden lower than 50% were more likely to die than nondiabetic patients with a similar or higher percentage of plaque burden. Overall, patients with diabetes and both potentially obstructive and nonobstructive plaque had an elevated risk of mortality compared with nondiabetic patients.

Although the small study sample did not allow investigators to truly predict mortality in patients with diabetes, CTA helped them discriminate some nuances of plaque disease and provided information that would not have been available through other means, according to Lin. As cases pile up, researchers hope to be able to determine the true value of CTA for clinical management, she said.

"We are not yet at the point where we can use CTA to discriminate among diabetic patients, but it helps us explain their increased mortality," Lin said. "This is only a step, but it's a promising step toward risk stratification with CT that we have already experienced with other imaging modalities."