Lasers and tips and drills, oh my!
You might think of high-tech hardware stores, or even of the annual gem-and-mineral show, when you hear what's happening in medicine to open clogged blood vessels. Researchers are studying the use of lasers, dentistry-type drills and sapphire-tipped catheters to remove the plaque made of cells and cholesterol that can form inside arteries. They also are testing sound waves and heat to destroy unwanted buildup.
"Return of the occluded artery' could be the title of a horror film viewed too often by cardiac patients and physicians. For example, of the estimated 150,000 balloon angioplasties--in which balloon-tipped catheters force open blocked arteries-- performed this year in the United States, more than 30 percent will have to be followed by vessel renarrowing within seven years, according to a recent study (SN: 5/16/87, p.311). To help prevent this, physicians have used aspirin and other blood-thinning drugs. Others report preliminary success with preventive administration of dietary fish oil to minimize vessel constriction and blood clotting that might lead to blockage. But some scientists are trying to improve the angioplasty procedure itself or supersede it with other techniques.
Conventional angioplasty sometimes leads to plaque fragmentation and the possible release of "chunks' large enough to block blood flow elsewhere in the body. By adding a laser to the system, say scientists, physicians may be able to smooth rough spots on vessel walls with heat and melt plaques rather than break them into pieces. Some experimental laser catheters consist of optical fibers tipped with sapphires that focus the heat; others use tips of gold or other heat-conducting materials.
Physicians at the San Francisco Heart Institute at Seton Medical Center have used these same principles to "weld' together human arteries with lasers, a possible suture-replacing procedure they've performed in more than 15 patients this year. Several researchers said that data from these and other laser studies in animals and a handful of human patients look promising.
With a sound-wave-emitting lithotriptor machine that disrupts kidney stones, researchers at Cedars-Sinai Medical Center in Los Angeles caused "mini-explosions' of the calcium and clotting proteins found in plaque along vessel segments excised for the experiments. But half the segments also tore, so Robert J. Siegel and his co-workers built a modified machine with a probe that can be aimed at the blockage--and shattered plaques within 2 to 60 seconds with much less damage to vessels. Particles shed by the exploded plaques apparently are small enough to be safe, says Siegel.
In other work, the whining noise made by a "mechanical rotational atherectomy device' is reminiscent of a dentist-office serenade, but the device drills through arterial plaque, not teeth. Scientists at Baylor College of Medicine in Houston have now reported results from the first use of the drill in humans. Threaded through vessels with a catheter as in angioplasty, the drill rotates at 120,000 rpm and removes rather than compresses plaque. In the seven patients treated, vessel blockage was reduced from 90 percent to less than 20 percent. Studies show that debris particles usually are the size of dust and are harmless, says Baylor's Nadim Zacca.
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|Title Annotation:||new techniques to open blocked arteries|
|Author:||Edwards, Diane D.|
|Date:||Dec 12, 1987|
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