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All of these procedures are methods to open up a narrowed or occluded artery without resorting to open heart surgery. They are collectively known as transcatheter revascularization or percutaneous coronary intervention (PCI). They generally require staying only one night in the hospital. There is almost no recovery period required. Normal activities can be resumed soon thereafter.
These techniques are more effective than medications in controlling angina. Furthermore, medications help the heart cope with the blockages but do not make the blockages go away.
The nature of the procedure and patient preparation is similar to that of a diagnostic angiogram. They do not require that the patient be put to sleep. The only difference is that the catheters actually enter the diseased artery whereas in a diagnostic angiogram the catheters terminate at the entrance to the artery. When the procedure is being done, blood flow through the artery is temporarily blocked so some angina may be felt.
The earliest technique -but still widely used and successful-is plain old balloon angioplasty (POBA). Here, a balloon at the end of the catheter is inflated while the catheter tip is crossing the narrowed segment of the artery. This expands the artery, cracks the atheromatous buildup and crushes it against the wall of the artery.
Sometimes after doing POBA another balloon catheter that has a metal mesh collapsed around the balloon it is placed into the artery. This metal mesh is called a stent. When this balloon is inflated, the stent expands out onto the wall of the artery and becomes incorporated into the wall.
Some areas of narrowing are very hard and calcified. A balloon will not be able to expand out against it. In this case, a rotoblator may be used. This is a catheter with a spinning drill bit on the end that cores right through the narrowed area. The area may subsequently be stented.
An atherectomy catheter will actually cut out a piece of the atheromatous material that's narrowing the artery. This material can be retrieved from the cutting edge of the catheter when the catheter is removed. Laser catheters use laser energy to cut through the atheromatous narrowing. These two techniques have not been found to be superior to the first three techniques mentioned but appear to have a niche role in particular circumstances.
The major drawback of all transcatheter reveascularizations is that the narrowing may reoccur, generally within 3 to 6 months. This is called restenosis. The incidence of this is has been anywhere from 18% to 40% per lesion dilated. Newer stents emit a chemical compound which makes restenosis much less likely to occur. These are called drug eluting stents.
If restenosis occurs, the procedure can be repeated. Restenosis is not due to rapid redevelopment of atherosclerosis. It is due to elastic recoil of the dilated vessel wall as well as an overgrowth of the cells lining the artery in response to the irritation caused by the catheter.
Radiation delivered to the stent site decreases the risk of restenosis even further by preventing the overgrowth of cells lining the dilated artery. This is accompished by temporarily placed a beta or gamma radiation emitter into the coronary artery following an angioplasty or stent procedure. This radiation procedure is called brachytherapy.
Lowering homocysteine levels with aggressive vitamin therapy (one mg of folic acid plus 10 mg of pyridoxine plus 400 micrograms of vitamin B 12) daily for the six months immediately following the angioplasty helped prevent restenosis in some early studies but further studies have not confirmend this effect..
Gene therapy is also being experimented with. Researchers are developing methods to deliver genes to the site of the angioplasty to inhibit the cellular overgrowth that causes restenosis.
A medicine not currently available in the United States, called Probucol, is an antioxidant that also protects against restenosis. Preliminary studies suggest that an antiplatelet agent called cilostazol may also protect against restenosis.
Not all narrowings are amenable to transcatheter approaches. In that case, the remaining options are medical therapy or bypass surgery.
There has been debate about the optimal approach for patients with multiple areas of narrowing. Using a transcatheter approach for all of the lesions is cheaper than a bypass and gets the patient out of the hospital faster. Plus, there is little to no recovery period. However, as each lesion treated with traditional stents has an 18%-40% chance of restenosis, there is a significant likelihood of having recurrent symptoms and needing repeat procedures in the future. The cumulative costs and rate of complications eventually becomes similar to that of a bypass operation. The availability of drug eluting stents is expected to significantly decrease the rate of restenosis and make transcatheter therapy for multiple lesions more successful.
A bypass operation requires more time in the hospital and a lengthy recovery period. But, once a person has completed their recovery, they can generally count on years of being symptom free and not needing any repeat procedures.
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