Leg Arteries

Tiny Razor Cleans Out Leg Arteries

WASHINGTON (AP) -- Doctors using a razor the size of a grain of rice are shearing ribbons of yellowish sludge from inside clogged leg arteries. It's the latest therapy for a hard-to-treat disease that slowly chokes off blood flow in millions of people's legs.

And the shavings it extracts are more than icky evidence of illness: A drug giant is buying this plaque for research on how to keep arteries from clogging in the first place.

Peripheral artery disease, or PAD, afflicts at least 12 million Americans as their leg arteries stiffen and narrow. Eventually, the lack of blood flow to muscles causes an aching pain while walking, called claudication. In severe cases, patients can hobble no more than a block or two.

Worse, PAD leads to about 150,000 amputations a year as arteries become completely blocked.

More than mobility is at stake: Having PAD increases the risk of a heart attack or stroke sevenfold - if leg arteries are clogged, other blood vessels almost certainly are, too.

Yet trouble walking often is wrongly considered a sign of aging instead of disease, meaning too few patients seek help early.

Clogged legs can be harder to alleviate than clogged heart arteries. Balloons threaded inside arteries, called angioplasty, to push aside the plaque and the use of scaffolding-like metal stents to hold arteries open don't work as well in the legs, where "restenosis" or reblockage with scar tissue or new plaque can occur quickly. The final option is a leg bypass, open surgery to reroute blood flow around the blockages.

Two new technologies offer the hope of better alternatives:

-The tiny razor, called the SilverHawk, is threaded in a catheter through patients' arteries to the blockages. Then the blade emerges and begins shaving; plaque collects in the device's tip for extraction.

In a registry tracking 335 patients for a year so far, 79 percent have needed no further treatment of the shaved-out areas, lead researcher Dr. Roger Gammon of Austin, Texas, announced at a major heart meeting last month. The razor even is credited with saving some particularly severe patients from imminent amputation.

-Cryoplasty is essentially an angioplasty on ice. Doctors inflate the angioplasty balloon with freezing nitrous oxide, better known as laughing gas. The cold is thought to inhibit cells in the artery wall from forming scar tissue, as well as make the plaque easier to push aside.

A study tracking 102 patients found that almost three years after their cryoplasty, 73.5 percent needed no further treatment - blood is still flowing well through treated areas, Dr. John Laird of the Washington Hospital Center reported at last month's Transcatheter Cardiovascular Therapeutics meeting.

Neither option has been directly compared to older treatments to prove how long the effects last, cautions Dr. William Gray, a PAD specialist at New York-Presbyterian Hospital/Columbia University Medical Center.

"Both of these devices are promising. The kicker is long-term durability," Gray says.

More intriguing, pharmaceutical giant Merck & Co. is buying some SilverHawk patients' extracted plaque, in a $9 million contract with razor manufacturer FoxHollow Technologies that, if the collaboration pans out, could generate up to $31 million more.

Why? Cholesterol and blood pressure are among the risk factors for cardiovascular disease, but they're not the only determinants: Some heart attack sufferers seem healthy right until they're stricken. Understanding what causes different kinds of plaque to form, at a genetic level, could lead to better ways to prevent atherosclerosis, whether it occurs in the legs or the heart arteries.

Plaques "are tissue deposits that have their own little biological drivers," explains FoxHollow founder Dr. John Simpson, a California cardiologist.

In addition, Merck sees the potential of recruiting SilverHawk patients for drug studies - allowing analysis of plaque removed from one leg before taking a medication and from the other leg after taking it, to see if a drug directly affects the buildup.

"This is a real opportunity to advance the science of understanding plaque biology," says Dr. Richard Pasternak, Merck's vice president of clinical research.

- AsiaOne, 31 Oct 2005.