Carotid ultrasound predicts stroke, heart attack risk

Evaluation of carotid artery plaque density performed on serial ultrasound scans could help identify patients at high risk for a heart attack or other adverse cardiovascular events, according to Austrian researchers.

Physicians know that the majority of cardiovascular and cerebrovascular events occur in patients whose blood vessels are less than 70% narrowed. Determining the degree of stenosis is thus insufficient to predict a patient's risk of suffering a heart attack or stroke, said lead researcher Dr. Markus Reiter of the department of angiography and interventional radiology at Medical University Vienna.

Reiter's team evaluated the complementary clinical value of computer-assisted gray-scale median (GSM) ultrasound measurements to determine carotid artery plaque density. Previous research suggested that plaque that appears dark on ultrasound images and has a low GSM level could be unstable and thus associated with an increased risk for clinical complications. Study results strengthened this theory.

"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 with patients with increasing GSM levels," Reiter said.

Reiter and colleagues enrolled 1268 asymptomatic patients at high risk of cardiovascular disease who underwent GSM measurements of their carotids. Scans showed that 574 patients had carotid artery disease, based on their plaque volume. Each of those patients had a second ultrasound exam six to nine months later to measure plaque changes.

The investigators found that GSM levels decreased in 230 of patients at follow-up. Eighty-five (37%) of those patients experienced a major adverse cardiovascular event such as heart attack, stroke, cardiac surgery, or other intervention within three years of the second ultrasound. In 344 patients, GSM levels increased between the baseline and follow-up exams. Ninety-two (28%) of those patients suffered a major adverse cardiovascular event.

Results also showed that vulnerable plaque in the carotid artery was not only an indicator of increased risk of stroke but was also associated with disease progression elsewhere in the cardiovascular system. Study results will appear in the September issue of Radiology.

Additional studies are needed to validate these findings. In the meantime, however, measuring GSM levels on serial ultrasound scans may be a noninvasive way to identify the presence of vulnerable plaques and bolster therapeutic effectiveness, according to Reiter.

"This technique will give us additional information to use in selecting patients that need aggressive treatment," he said.

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