MRI scan to gauge heart attack risk
(New Scientist Via Acquire Media NewsEdge) MRI scans could soon be used to show who is at risk of a heart attack. At the moment the only way is to use an invasive probe that can itself trigger cardiac arrest.
A major cause of heart attacks is plaques made of immune cells and cholesterol that build up inside the coronary arteries, which feed the heart. If a plaque ruptures, a clot can form, blocking blood flow with potentially catastrophic results. While cameras can be sent into arteries to check the walls for plaques, the probe itself might rupture a plaque.
An MRI scan can see inside the body without risk, but doesn't provide enough resolution to image artery walls directly. However, Simon Robinson of Lantheus Medical Imaging in North Billerica, Massachusetts, and his colleagues found a way around this using gadolinium chelate, a substance which is already used to light up blood in MRI scans.
They attached this "contrast agent" to a molecule that binds to the protein elastin, which is found in artery walls. When injected into the bloodstream of pigs, the resulting molecule binds to elastin throughout the thickness of the artery walls and lights them up in an MRI scan (see image).
The plan is to image the arteries of people thought to be at risk of heart attack and check for a dangerous amount of thickening that would suggest the presence of plaques. "If you've got a plaque developing, you'll see a brighter, thicker region," Robinson says.
Patients with plaques could be given cholesterol-lowering drugs, such as statins, blood thinners that prevent a clot from forming if a plaque ruptures, or fitted with a stent to support artery walls and lower the risk that a plaque will burst. The gadolinium chelate eventually detaches from the artery walls and is cleared by the kidneys.
"There is an enormous need for new ways of imaging these plaques, which contribute to stroke, heart attacks, renal disease and peripheral vascular disease," says radiologist Mohammed Hamady of St Mary's Hospital in London.
Lantheus is conducting safety trials of the contrast agent and hopes to begin tests in humans early in 2010. One possible obstacle is that some gadolinium-based contrast agents have previously been linked to kidney problems.
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