Cleaning Up Nasty Clots
Researchers find new ways to stave off strokes
Rushing through healthy vessels, blood brings life. Clog those vessels with a clot, however, and blood brings danger and death in the form of a stroke. A particularly mean type strikes 125,000 Americans every year: Chips from a massive clot in the heart break off and lodge in the brain, starving it of blood. And if that doesn't do enough damage the first time, just wait, because another chip is likely to break off.
But last week researchers proposed a new way to detect these so-called cardioembolic strokes and help avoid a fatal sequel. By adding a magnetic resonance imaging scan to conventional tests, doctors can find nearly twice as many of these deadly clots, John Sheehan, a cardiac radiologist at Northwestern Memorial Hospital in Chicago, told a meeting of the Society of Interventional Radiology in Seattle. Radiologists also heard about a method to vacuum up other types of clots-clumps in leg veins, similar to the malady afflicting Vice President Dick Cheney last week but much, much worse.
With strokes, "the problem is that in as many as half the patients we see, we can't get a clear sense of the cause," says Steven Warach, a neurologist at the National Institute of Neurological Disorders and Stroke. Ignorance spells particular trouble in a cardioembolic stroke. "With the heart pushing and pounding at the clot, it tends to be unstable, and more pieces break off," Sheehan says.
Usually a stroke patient's heart is examined with an echocardiogram, which uses sound waves to make images. In a test of 93 patients who had both that and MRI, the MRI detected more clots and heart damage that could lead to them. Sheehan doesn't advocate replacing echo tests but rather adding MRI. If clots are detected, patients can be treated with strong anticoagulant drugs like warfarin.
But Robert Hart, an expert in cardioembolic stroke at the University of Texas Health Science Center in San Antonio, worries the study "is small, and it's not clear that what an MRI calls a clot is really a clot." False signals could have made the method seem better than it really was. Warach, however, says it's a good start, and "in 10 years I wouldn't be surprised if we're all doing these tests."
A new device called an Angiojet may help break down another kind of clot, deep vein thrombosis in the leg. It's only for massive blockages that extend the length of the leg. (Typical leg clots, like Cheney's, are tiny.) Radiologists snake a tube into the vein to spray a clot-dissolving drug while a vacuum in the tube sucks the debris out. In a study of 102 patients, this succeeded in 83 percent. Again, researchers caution that bigger studies need to be done-and that this one was funded by the device maker-but the vacuum could eventually get a few patients back in the flow.
This story appears in the March 19, 2007 print edition of U.S. News & World Report.
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