STENT: Device to prop open arteries may prove major heart treatment advance
Device to prop open arteries may prove major heart treatment advance
By
Craig M. Walker, M.D.
Medical Director,
Cardiovascular Institute of the South
Relatively few medical devices truly revolutionize the treatment of disease. But the Food and Drug Administration has recently approved one for general use that may greatly change the future non-surgical treatment of heart patients.
The device is the Palmaz-Schatz stent -- a tiny, expandable stainless steel tube which holds heart arteries open following angioplasty. Of all the devices to be spawned by the cardiovascular technology boom of the 1980s, I think stents in general, and this one in particular, will prove to be the most important. That's not idle speculation: Cardiovascular Institute of the South has been one of very few centers in the nation which has been actively involved in the clinical development of not only stents, but virtually all the promising new technologies for treating atherosclerosis -- the blood flow-constricting buildup of cholesterol plaque in the arteries.
The standard nonsurgical treatment for these blockages is angioplasty, in which a tiny balloon at the tip of a catheter is moved into position at the blockage site and inflated, flattening the plaque against the artery wall. While far less traumatic and costly than bypass surgery, angioplasty has one significant shortcoming -- a fairly high failure rate.
In one to two percent of patients, the artery snaps shut immediately following angioplasty, triggering a heart attack. Heretofore, the only option at that point has been emergency bypass surgery. Now the cardiologist may be able to simply implant a stent to hold the collapsed section of artery open.
In about a third of angioplasty patients, the blockage returns within the first six months, due to restenosis -- new plaque deposits or clot formation caused by the rough and irregular opening typically created by angioplasty, or by thickening of the artery wall as a response to the stretching of the artery.
The stent creates a more regular opening, pins down any torn segments of artery lining resulting from the angioplasty and, by creating a slightly oversized opening, reduces the effects of wall thickening. The stent also greatly increases the long-term success of angioplasty in the restenosis-prone sections of vein or artery used as bypass grafts.
The unexpanded Palmaz-Schatz stent is mounted over a standard angioplasty balloon, and worked into position within the former blockage site by a catheter. The balloon is inflated, expanding the stent, then is deflated and withdrawn, leaving the stent permanently in place.
While stenting involves essentially the same process as balloon angioplasty, the stent is larger and less flexible than the normal balloon catheter, and threading it into position is thus more difficult. So the cardiologist must plan his cases carefully and become even more adept at maneuvering catheters if he is to apply it successfully.
Present FDA stenting guidelines require that patients be placed on anti-clotting medications for several weeks, until the stent is overgrown by the artery lining. That slightly increases the length of hospital stay and the costs of the procedure. But reports of high European success rates for stenting without anticoagulants may eventually change that requirement, making it even more cost effective.
©1999 Cardiovascular Institute of the South
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