SCIENCE FILE : MEDICINE : Trial Balloon : A New Technique Uses an Inflatable Catheter to Unclog Arteries in Stroke Victims, but Its Use in the Brain Is Highly Experimental.
Ten years ago, Dr. Robert Ferguson conducted an improbable experiment. Using balloon angioplasty, a technique to unclog coronary arteries, he tried to open a blocked artery in a stroke victim’s neck.
The patient thrived, but Ferguson, a radiologist at Baptist Memorial Hospital in Memphis, was practically run out of medicine for taking the therapeutic gamble, which he believed was justified because the patient also had cancer, making him ineligible for standard surgical therapy.
“There was great doubt that this made any sense,” Ferguson said. “They were incensed that I was doing this.”
What a difference a decade makes. Last month, at an American Heart Assn. meeting in Anaheim, medical researchers hailed the 40-year-old Ferguson as a “star,” the pioneer of a promising new treatment for strokes, America’s third leading cause of death.
“Innovative” and “terribly exciting,” Dr. James T. Robertson, a University of Tennessee neurosurgeon, said of the approach. But, he added: “It’s still unproven.”
Dr. William M. Feinberg, a neurologist at the Arizona Health Sciences Center, was among the skeptics. “I was concerned that when you blow up a balloon inside the artery, you’ll actually end up causing the very thing you’re trying to prevent, which is a stroke,” he said. “But that doesn’t appear to happen as frequently as we had feared.”
Feinberg now predicts that balloon angioplasty and related artery-probing techniques will play a role in stroke therapy and prevention. And its impact could be substantial, he said, because complications from stroke, from impaired vision to outright paralysis, make it not only a leading killer but “the major cause of adult disability” in the United States.
Although recent studies on ballooning into neck arteries--and into the brain itself--seem promising, the technique’s long-term safety and effectiveness have not been established. Indeed, Ferguson says he is concerned that many doctors will start applying the technology before they fully grasp the dangers of ballooning in the brain.
A stroke occurs when a blood vessel in the brain is blocked or ruptured. The balloon treatment is aimed at so-called thrombolytic stroke, which is five times more common than the hemorrhagic, or bleeding stroke, and also much harder to prevent.
In a thrombolytic stroke, a bit of dislodged plaque or other arterial debris floats upstream into the brain, eventually sticking in a blood vessel and triggering a clot reaction. That starves brain cells of oxygen-carrying blood. Depending on where the blockage happens, symptoms can be as mild as passing numbness or as profound as permanent paralysis.
Because brain damage is irreversible, the main goal of treatment is to prevent a future stroke. The standard surgical treatment, called carotid endarterectomy, involves opening the carotid artery, the source of most of the clot-forming debris, and scraping out plaque. But not all stroke victims are healthy enough for such surgery.
That is where this new approach comes in. Ferguson gingerly inserts a four-foot-long, plastic-coated, balloon-tipped catheter wire through an incision in the patient’s groin, then finagles it into an artery and up through the torso. When the balloon reaches the plaque-narrowed carotid--as depicted by a moving computerized X-ray on a monitor--Ferguson inflates the balloon for a few seconds, compressing the plaque against the artery walls.
He told the heart meeting that he and his colleagues at four other medical centers had used the technique on 147 patients--none of whom were eligible for surgery--doubling the width of the narrowed carotid arteries of 83% of them.
Overall, he said, about 4% of patients experienced a stroke or died in the month after treatment. That rivals the reported 3% complication rate of carotid surgery. The balloon technique, said Arizona’s Feinberg, “is going to have to be very safe before it replaces surgery.”
Meanwhile, Ferguson and other physicians have taken the next step, venturing into the brain with balloon-tipped catheters.
This is a foray into uncharted territory because no other therapy is available when a clot seals off those out-of-reach blood vessels. Not even clot-dissolving drugs always make it to where they are needed in the brain.
“There is nothing for certain for treating blocked or narrowed arteries in the head,” said University of Tennessee’s Robertson.
By now, the multi-center research team that Ferguson is part of has performed the balloon technique on cerebral arteries of about 50 patients. The technique successfully widened the affected arteries in about 75% of those treated, while 19% had a stroke or died within a month, Ferguson said.
Although that complication rate may sound like a disaster, Ferguson explained that the patients were among the very sickest to begin with, some of them in the midst of a stroke when the procedure was performed as an emergency treatment. “Our data appears to show that it is a reasonably safe therapy,” Ferguson said.
In addition to balloon angioplasty, Ferguson and his colleagues have borrowed another technique from the cardiac catheter lab: propping up a clogged or collapsed blood vessel with a piece of artificial blood vessel known as a stent. That involves snaking a stent-tipped catheter to the trouble spot in the carotid artery or brain and then using the balloon to expand the stent in place.
More than 100 patients have received a stent in the carotid artery, Ferguson said, but only a few have had one installed in a brain blood vessel. The first patient that Ferguson treated with a brain stent was a middle-aged man with numbness of the face and tingling in the arms. X-rays and brain scans revealed a nearly clogged stretch of artery below one eye.
Soon after a balloon widened the artery and a stent was installed, Ferguson said, the man’s symptoms cleared up. Imaging tests confirmed that the artery was wider and that blood flow was largely restored.
“Even I had trouble believing it could work,” Ferguson said, given how inaccessible and delicate cranial blood vessels are. “I’m very optimistic that this will someday be an important part of our therapeutic armamentarium.”
Buoyed by his early results and a bit surprised by his sudden fame, Ferguson says he is now more worried about the balloon and stenting procedures catching on too quickly among stroke doctors. No long-term studies have been done on how long recipients of the experimental therapies live. If they live no longer than comparable patients who were not treated, or were treated by carotid surgery, than the technique, for all its noninvasive appeal, is a wash.
Worse, Ferguson fears that doctors will try it without proper training, thinking that navigating a catheter into the neck or brain is the same as probing coronary arteries.
“Nothing could be further from the truth,” he said.
For instance, the brain’s narrow blood vessels, being especially thin and delicate, are more apt to tear in such a procedure. He says he would not have tried the procedure unless he had been trained in radiology and neurology.
In fact, he says he just heard of an untrained physician who leaped at the chance to use the balloon procedure on a carotid artery--and inadvertently gave the patient a massive stroke. He advises potential patients not to undergo the procedures except as part of a controlled clinical study approved by a major academic medical center.
Ironically, the former medical outcast is now trying to slow down the spread of the procedure he pioneered.
“This looks very promising, but we need to bring order and planning to its acceptance,” he said. “It will be a tragedy of epic proportions if this runs away from us and people start doing it just for money or fame.”
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
NEW ATTACK ON STROKE
In the most common type of stroke, a blockage forms in one of the delicate arteries feeding the brain, depriving tissue of oxygen. The blockage is most often a clot or plaque that narrows the artery and reduces blood flow.
Two experimental therapies, originally developed for coronary artery disease, offer new promise for clearing arteries to prevent strokes.
1) Balloon angioplasty involves inserting a tiny deflated balloon into an artery in the groin (through a surgical incision) and snaking it through the carotid artery of the neck and into the brain.
A surgeon relying on x-ray images of the brain locates the diseased artery, slips in the deflated balloon and inflates it, expanding the blood vessel to improve circulation.
2) The second method is very similar, but instead of a balloon a narrow synthetic tube, or stent, is placed into the constricted cerebral artery. The tube acts as an artificial blood vessel.
