Peripheral artery disease afflicts at least 12 million Americans, causing unbearable pain due to leg arteries being clogged with plaque. Now there are two new treatments for PAD-a tiny plaque-shearing razor called the SilverHawk.
By Carol Johnson
When older patients go to the doctor complaining of pain while walking, often their pain is misdiagnosed as simply being a sign of aging. And many people assume that diagnosis without even going to the doctor. But leg pain could be a sign of a serious condition called peripheral artery disease, or PAD. When leg arteries stiffen and narrow because of plaque buildup inside, blood flow to muscles is diminished. That lack of blood causes an aching pain while walking, called claudication, and in severe cases patients can hobble only a block or two before the pain overtakes them.
Because most patients don’t seek help early, arteries can come completely blocked. PAD leads to about 150,000 amputations each year. But going without treatment can affect more than just mobility. PAD more than quadruples the risk of a heart attack or stroke. It naturally follows that if leg arteries are clogged, then other blood vessels must also be clogged.
A treatment for clearing arteries in the heart, angioplasty has been used successfully for years. In angioplasty a tiny balloon is threaded inside the artery to push aside the plaque. But angioplasty is difficult to accomplish in the legs, because the metal stents used to hold arteries open don’t work as well in leg arteries, where “restenoisis”-reblockage with scar tissue or new plaque-can occur quickly.
Two new technologies have been offering hope to patients suffering from this hard-to-treat disease:
- Cryoplasty is essentially an angioplasty procedure on ice. Instead of water, the doctor inflates the angioplasty balloon with freezing nitrous oxide, better known as laughing gas. The low temperature of the gas firms the plaque and makes it easier to push aside, while inhibiting cells in the artery wall from forming scar tissue. A study reported by Dr. John Laird of the Washington Hospital Center tracked 102 PAD patients who had been treated with cryoplasty. Almost three years after their procedure, nearly 75% of the patients needed no further treatment, and blood is still flowing well through treated areas.
- A tiny razor called the SilverHawk, only the size of a grain of rice, is threaded in a catheter through patients’ arteries to the blockages. Then the blade emerges and begins shearing off ribbons of the yellowish sludge, with the device’s tip collecting up the plaque to extract it. Dr. Roger Gammon of Austin, TX, announced last month the results of a registry tracking 335 patients for a year, and so far nearly 80% have needed no further treatment of the shaved-out areas.
The SilverHawk razor has even been credited with sparing some particularly serious patients from amputation they would certainly have had to have without the razor treatment. Although neither option has yet been directly compared to older, established treatments for PAD to see how long the effects will last, a PAD specialist at New York-Presbyterian Hospital/Columbia University Medical Center feels optimistic. Dr. William Gray says, “Both of these devices are promising. The kicker is long-term durability.”
Interestingly, pharmaceutical giant Merck & Co. has entered into a $9 million contract with the manufacturer of the SilverHawk razor, FoxHollow Technologies, to buy some of the extracted plaque from PAD patients. The company plans to use the plaque to research how to keep arteries from clogging in the first place. If the collaboration between the two companies continues, it could generate up to $31 million more for research. Since some heart attack sufferers seem healthy right until their attack, it is essential for scientists to discover what causes different types of plaque to form, so they can develop better ways to prevent atherosclerosis whether it occurs in the arteries of the legs or of the heart.
If Merck develops a promising pharmaceutical treatment for controlling plaque buildup, they will need test subjects to participate in clinical trials. The company may recruit SilverHawk patients for drug studies so they can analyze the plaque taken from one leg before taking a medication, and then analyze the plaque taken from the other leg after taking the medication, to see if the drug significantly affects plaque 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.