FDA Testing Limits of Medical Technology

Monday, September 13th 2004, 10:56 am
By: News On 6

WASHINGTON (AP) _ A little-known Food and Drug program is testing the latest medical technology to determine how safe and useful it can be.

One cutting-edge experiment is designed to see if injecting certain drugs directly into diseased arteries works better than commonly used stents in keeping arteries clear.

Dr. William Pritchard painstakingly threads a thin tube deep into his sedated patient's beating heart. Then, in a radical move, he pushes a hair-sized needle out of the tube and deliberately punctures a crucial artery.

But a pink snout beneath the sheets signals this is no ordinary operating room _ or patient. Working on the pig are FDA scientists.

The agency is best known as the nation's medical gatekeeper, approving the sale of new treatments rather than actually researching them. Indeed, proving that a therapy works well enough to sell is, by law, the job of the treatment's official sponsor, usually the manufacturer.

Still, in a scattered warren of laboratories, 140 FDA scientists are pushing medical devices to their limits so the agency is not totally dependent on manufacturers to learn about pitfalls before approving sales. The scientists' work also is intended to find solutions when problems arise with technology already on the market.

``There's a need for independent research,'' said Larry Kessler, who directs the $21 million Office of Science and Engineering Laboratories.

In one room, scientists ``fry'' fake brains in an MRI machine, studying how dangerous the scanners are for the growing number of people with metal implants.

In a different room, government sleuths pull apart a counterfeit surgery mesh, testing the illegal product's durability to be sure it will not break apart inside patients who unwittingly received it.

The research goes beyond basic medicine.

These labs are where the Federal Aviation Administration came to learn which walkthrough metal detectors are safest for airline passengers with pacemakers.

It is where regulators turned last year before ordering that cell phones be made compatible with hearing aids, to ensure the change could be done.

Most unusual is the barnyard, nestled behind a locked fence in rolling farmland just outside of Washington. It is home to pigs, and sometimes sheep, that Pritchard and physiologist John Karanian use to test new technology for heart disease because those animals' hearts are so human-like.

The scientists pick potentially hot technologies such as that tiny, drug-filled heart needle _ called a microsyringe _ for hands-on probing so concerns can be uncovered before studies on vulnerable patients ever begin.

``The idea is to get from concept to bedside as quickly as possible,'' said Karanian, who heads the FDA's large-animal lab. ``If you identify some potential failure modes, safety issues, you allow the right questions to get asked. That is of great public benefit.''

The animals also offer training for FDA engineers who approve medical devices.

Someone evaluating a fragile new heart catheter, for example, may not spot a design flaw that could make it break inside a patient if the researcher has never tugged the device through the tough crooks and turns of real arteries, Pritchard said.

Also, animal research can help determine what went wrong when devices unexpectedly fail.

Consider Ancure, a patch for the body's largest blood vessel. The product was pulled from the market last year after 12 deaths and thousands of malfunctions that its maker acknowledged hiding from FDA.

``The question is, what did we miss and how did we miss it?'' Pritchard said.

Even makers of medical equipment often are surprised at the animal lab, which opened in 2000.

EndoBionics Inc. scientists were stunned when Karanian called to say he was studying whether their microsyringe could inject estrogen into heart arteries to prevent reclogging. That was the very question the company was trying to answer with its own testing. EndoBionics scientists quickly hopped a plane from California to watch the FDA's work.

``They're doing amazingly advanced research,'' said Kirk Seward, the company's chief technology officer.

Karanian's preliminary results, presented at medical meetings this summer, suggest the approach may work. It is data that EndoBionics can use in its quest to begin human studies this fall.

Today, cardiologists typically clean out fat-clogged heart arteries and prop them open with tiny metal scaffolds called stents. They are not perfect; scar tissue can form around stents and arteries can reclog 30 percent of the time.

Newer, more expensive stents emit drugs to lower the reclogging risk.

But FDA tests show much of the stent-released medicine goes into the bloodstream instead of staying on the irritated artery wall where it is needed, engineer Joseph Hutter said. His lab is modeling that dilution to determine how much medicine needs to get into artery tissue _ steps to better evaluate new stents.

By injecting a clog-blocking drug directly into the artery wall, Karanian said, ``We might be able to eliminate the use of permanent implants.''

Endobionics' microsyringe is small enough to maneuver deep into heart arteries and try. That is where the pigs come in.

First, Karanian threaded a tiny balloon into a 70-pound pig in the FDA's hospital-like operating room. Because the pig's arteries are not naturally clogged, Karanian simulated the damage that occurs in people. He rubbed the inflated balloon back and forth, irritation that spurs scar tissue formation.

Could estrogen, thought to promote artery-wall healing, prevent that scar tissue? To see, Pritchard must inject it with pinprick accuracy, threading in a tube encapsulating the microsyringe.

At the right spot, he popped out the teeny needle, piercing the artery. Seconds later, estrogen spewed through the almost microscopic hole, a light colored cloud on the overhead X-ray screen.

Thirty days later, opening the pig's arteries showed the injected estrogen indeed prevented clogs from forming.