A simple, inexpensive ultrasound could help doctors determine a patient's risk for having a heart attack.

Researchers in Austria used ultrasound imaging to measure the plaque on the carotid arteries of over 1,200 patients. They followed up six to nine months later with the 574 patients who had carotid artery disease, measuring the changes in the density of the plaque.

They found those with an increase in plaque density had a much higher rate of heart attack within three years than those who had a decrease in plaque density.

Researchers say more studies are needed, but ultrasound could prove to be an important tool in determining which patients need aggressive treatment.