Stanford Report, October 18, 2000
|New treatment for
re-narrowing of heart arteries after angioplasty under trial
BY CHARLES CLAWSON
new procedure being studied at Stanford may provide the next
generation of treatment for coronary artery disease. The Galileo
Inhibit Study, as it's called, focuses on
Before the mid-80s anyone suffering severe blockage of the arteries on the heart faced the prospect of open-heart surgery. Then came the invention of angioplasty, a minimally invasive procedure in which a blocked artery is opened by inserting a small balloon in the blood vessel. In 1994 a procedure called "stenting" came into use, whereby a stent a kind of metal scaffolding is mounted on the balloon used in angioplasty and then left in the blood vessel after the balloon is removed.
The current study treats patients who suffer re-narrowing of these treated areas, what is termed "in-stent restenosis" (re-blockage of the arteries within the stent). While stenting has reduced artery re-blockage after angioplasty from about 50 percent to 20 percent (results vary), once a stent re-narrows, the chance of re-renarrowing is upward of 60 percent. The Galileo system is intended to drastically reduce this final rate of recurrence.
"The re-narrowing of these treated areas is caused by an accumulation of tissue from injury to the blood vessel," explained Alan Yeung, MD, director of the Cardiac Catheterization and Interventional Laboratories at Stanford. "This is a similar phenomenon to keloid formation. Several studies have shown that radiation is helpful in preventing this tissue from re-growing."
Under the Galileo system, beta radiation is delivered to these areas of re-blockage by using a small wire coated with a source of radiation. The wire is inserted into a balloon and placed in the bloodstream of a patient for two to five minutes. Because beta radiation as opposed to gamma radiation has a very specific, well-defined penetration range, its delivery is highly controlled. No lead or concrete barriers are necessary, and staff can remain in the room when a patient is treated.
"Preliminary findings suggest a very low rate of re-restenosis," said Yeung. "It's a very promising technique no other method is available that treats restenosis effectively."
Currently, about 100 patients are involved in the trial, which is one month old. A phase I study, involving 108 patients who suffered first-time and recurring artery blockage, found that beta radiation therapy resulted in re-blockage rates of only 8 percent, compared with 39 percent for patients who received no radiotherapy.
Stanford is one of three
centers in the United States using the new system, which is
manufactured by Guidant Corporation in Santa Clara, Calif.