Ultrasound helps predict heart attacks in a low-risk population
NEW ORLEANS—By adding the results of an imaging technique to the traditional risk factors for coronary heart disease, doctors at Baylor College of Medicine in Houston were able to improve heart attack prediction in people previously considered low risk, according to a study presented Nov. 11 at the American Heart Association's (AHA) Scientific Sessions.

Researchers used ultrasound imaging to view the carotid intima media thickness (C-IMT).

“The ultrasound added another dimension to the risk factor score and showed us that those with thick arteries in the higher end of low risk group actually are at intermediate risk for coronary heart disease,” said the study’s lead author Vijay Nambi, MD, assistant professor of medicine, atherosclerosis and vascular medicine at Baylor.

Risk prediction is traditionally divided into three groups: low, intermediate and high risk, according to the researchers. Low risk is defined as having a less than 10 percent chance of developing coronary heart disease in the next 10 years; intermediate is a 10 to 20 percent chance of a coronary event in 10 years; and high risk is anything greater than 20 percent. The percentage is calculated using a score based on traditional risk factors which include age, gender, HDL cholesterol, total cholesterol, hypertension and smoking.

Nambi and colleagues followed more than 13,000 people participating in the Atherosclerosis Risk in Communities study designed to investigate the etiology and natural history of atherosclerosis. Participants in the current study were followed for almost 14 years.

After adding imaging to the traditional risk factors, the investigators said that those in the higher end of the low risk group (estimated 10-year risk of 5 to 10 percent) were found to have a greater chance of having a heart attack, especially if imaging revealed a thicker C-IMT.

Nambi said that about 4 percent of those who fell below the 5 percent estimated risk had a heart attack, while more than 13 percent of those in the 5 to 10 percent suffered coronary heart events. Furthermore, he pointed out that in the 5 to 10 percent risk group, those with the thickest arteries had approximately a 17 percent risk for coronary heart events during the 14-year follow up.

“There is a big difference between 4 percent and 13 percent,” Nambi said. “These results show us that we need to take a closer look at some of those individuals in the low risk category and even reconsider the definition of “low risk.”

"Being able to pinpoint those more likely to have a heart attack will allow us to take early, more effective preventive action to stop a heart attack before it happens,” said Christie Ballantyne, MD, chief of atherosclerosis and vascular medicine at Baylor.