The team led by Markus Reiter at Medical University Vienna in Austria performed ultrasound imaging on the carotid arteries of 1,268 patients who were asymptomatic but at high risk for cardiovascular disease.
By determining the amount of plaque built up in the two vessels that supply blood to the head and neck, 574 patients were found to have carotid artery disease.
"Determining the degree of stenosis, or how much the artery has narrowed, is insufficient to predict patient risk," said lead researcher Markus Reiter, M.D., from the Department of Angiography and Interventional Radiology at Medical University Vienna in Austria.
"We know that the majority of cardiovascular and cerebrovascular events occur in patients whose blood vessels are less than 70 percent narrowed," he added.
With the help of ultrasound images and computer-assisted gray scale median (GSM) measurements, the research team examined the density of the plaque lining the carotid arteries.
Plaques that appear dark on ultrasound images and have a low GSM level are suggested to be associated with an increased risk for clinical complications and seem to represent unstable plaques, which are more likely to rupture or burst.
The study's follow-up ultrasounds revealed that GSM levels had decreased in 230 (40 percent) of the patients. Of those, 85 experienced a major adverse cardiovascular event within three years of the second ultrasound.
In 344 of the patients, ultrasound GSM levels had increased between the baseline and follow-up ultrasound examinations. Of those patients, 92 experienced a major adverse cardiovascular event.
"Patients with a reduction in GSM levels from their baseline ultrasound to the follow-up ultrasound exhibited a significantly increased risk for near-future adverse event compared to patients with increasing GSM levels," said Reiter.
"This technique will give us additional information to use in selecting patients that need aggressive treatment," he added.
The study is published in the September issue of the journal Radiology.