Researchers have used a computer-assisted ultrasound program to identify soft plaque in the carotid arteries of high-risk asymptomatic patients at high risk for a heart attack or other adverse cardiovascular events, according to a study published in the September issue of the journal Radiology.
Markus Reiter, MD, and colleagues from Medical University Vienna in Austria used ultrasound images and computer-assisted gray scale median (GSM) measurements to determine 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.
"Determining the degree of stenosis is insufficient to predict patient risk," said Reiter. "We know that the majority of cardiovascular and cerebrovascular events occur in patients whose blood vessels are less than 70 percent narrowed."
Of the 1,268 patients imaged, 574 patients had carotid artery disease, as determined by the amount of plaque. Each of those patients had a second ultrasound exam six to nine months later to measure changes in the plaque.
The follow-up ultrasounds revealed that GSM levels had decreased in 40 percent of the patients. Of those, 37 percent experienced a major adverse cardiovascular event such as heart attack, stroke, coronary artery bypass, surgery or other intervention, within three years of the second ultrasound, according to the researchers.
In 60 percent of patients, the ultrasound GSM levels had increased between the baseline and follow-up ultrasound examinations. Of those patients, 28 percent 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,” Reiter said.
The authors wrote that the results showed that vulnerable plaque in the carotid artery was not only an indicator of increased risk of stroke downstream from the carotid artery, but also was associated with disease progression elsewhere in the cardiovascular system.
Although additional studies are needed, Reiter said that the measuring GSM levels on serial ultrasound examinations may be a noninvasive way to identify the presence of vulnerable plaques and may provide additional information to use in selecting patients that need aggressive treatment.