They write about the new technique, which can identify thickening of the coronary artery wall, in a paper expected to be published early online in the journal Radiology this week.
Coronary Artery DiseaseCoronary artery disease (CAD) is the most common type of heart disease and the leading cause of death in the US for both men and women.
It occurs when the arteries that supply blood to heart muscle harden and narrow as deposits of fat and cholesterol called plaques build up on their insides, a process known as atherosclerosis.
Eventually, the build up is so thick, it restricts blood flow to the point where the arteries can't supply the heart muscle with the nutrients and oxygen it needs, resulting in chest pain (angina) or heart attack. Most heart attacks happen because a blood clot suddenly cuts off the heart's blood supply, causing permanent damage to the heart muscle.
Difficult to Image Small VesselsLead researcher on the study, Khaled Z Abd-Elmoniem is a staff scientist in the Biomedical and Metabolic Imaging branch of the National Institute of Diabetes and Digestive and Kidney Diseases at NIH. He says in a press release issued on Tuesday:
"Imaging the coronary arteries that supply the heart with blood is extremely difficult because they are very small and constantly in motion."
"Obtaining a reliable and accurate image of these vessels is very important because thickening of the vessel wall is an early indicator of atherosclerosis."
Currently No Reliable Non-Invasive Measure of Early CADIn the longer term, CAD can also weaken heart muscle and contribute to heart failure and abnormal heartbeat and heart rhythm (arrhythmias).
By identifying the early stages of thickening of the blood vessel walls that precede artery narrowing, researchers believe it may be possible to intervene and reduce the risks of heart attack and other coronary events.
But, as Abd-Elmoniem explains:
"We currently have no reliable way to non-invasively image coronary artery disease in its early stages, when the disease can be treated with lifestyle changes and medications to lower cholesterol."
What the Researchers DidFor their study, the researchers used MRI to measure the vessel wall thickness of the coronary arteries in 26 patients of average age 48, half of whom were men. Each patient had at least one risk factor for CAD.
The team also enrolled another 12 healthy people of average age 26, three of whom were men, as controls. They were matched to the patients by body mass index (BMI).
The researchers compared two types of MRI to measure artery wall thickness. One was a single-frame scan that captures a single image, and the other captures five consecutive images, to increase the chance of getting one that isn't blurred. This second method is called "time-resolved multi-frame acquisition".
What they FoundThey found that time-resolved multi-frame acquisition produced a usable image 90% of the time, while the success rate for the single-frame method was only 76%.
The time-resolved multi-frame acquisition method was also better at detecting a significant difference in wall thickness between CAD patients and controls, with a smaller standard deviation, which is a statistician's way of saying the measurements are also more precise.
ImplicationsThe researchers suggest further studies should now be done to validate time-resolved multi-frame MRI.
Abd-Elmoniem says their results show MRI could be used to screen people at risk for CAD. It could also be a way to monitor the success of treatments.
He says measuring the thickness of coronary artery walls is a more direct way to assess early-stage CAD than doing blood tests to measure cholesterol and lipids in the blood, which can be indicators of atherosclerosis.
Written by Catharine Paddock PhD