Kate Simms wasn't one to let age slow her down. At 85, this Orange County, Va., resident was still making an occasional 50-mile-round trip to cook and clean for her older sister and enjoying the land east of the Blue Ridge that she calls her garden spot of the Earth. A hip replacement a few years back didn't stop her. Nor did angioplasty to clear a heart artery in 1993. But in March of last year, the pain in her legs did.

"It was a terrible hurt," said Simms, that kept her from all the things she loves to do. "It felt like it was snapping my legs in two from the knee joint to the ankle." She was no longer able to climb steps or walk in her lush flower gardens.

Simms was suffering from peripheral arterial disease (PAD), an often overlooked condition that blocks blood flow in the arteries of the legs. PAD affects nearly 8 million Americans, with symptoms of pain or swelling, difficulty in walking, numbness, skin discoloration and leg or foot ulcers that don't heal. It also can cause gangrene and loss of limb.

"Public awareness is very low," said Fritz Angle, an interventional radiologist at the University of Virginia Health Sciences Center in Charlottesville. "Often, as people grow older, they take for granted aches and pains as part of aging, and because the disease has a gradual onset it goes undetected."

Perhaps that's what happened to Simms, whose disease was advanced when diagnosed. In the earlier stages, patients experience intermittent dull aches or cramping on exertion--called claudication--because there is not enough blood flow in the legs. A few minutes rest usually eases the discomfort.

"They'll walk maybe 10 blocks and then the pain might start in the calf," said Siobhan Dumbleton, an interventional radiologist at the Hospital of the University of Pennsylvania in Philadelphia. "Often they will stop, rest and then continue walking, perhaps for eight more blocks before it starts again."

While doctors aren't sure what causes PAD, they do know that it can develop as a result of sclerosis, a group of disorders that cause thickening and loss of elasticity in the artery walls. Atherosclerosis, in which fat and cholesterol build up inside the arteries, is the most common type. PAD usually occurs after age 50, Dumbleton said, and risk factors such as smoking, high blood pressure, diabetes, excess weight, heart disease and inactivity can contribute to its onset.

In some cases, lifestyle changes can halt the disease's progression. If the patient has high blood pressure, for example, "we try to control their diet or get them to stop smoking," she said.

Exercise programs can build up what doctors call collateral flow, in which the blood system looks for ways around the blockage and develops collaterals, or small branches off the main artery. Swimming is very good for PAD patients, Dumbleton said, and some can manage their disease for many years with exercise and other lifestyle changes.

That's why Angle and Dumbleton recommend that individuals with leg pain request a simple screening procedure known as an Ankle Brachial Index, in which blood pressure is measured in both arms and legs and a medical history is taken in a search for symptoms. More advanced diagnostic screenings can include ultrasound or magnetic resonance angiography, which produce moving images of the internal organs and vessels, Dumbleton said.

Neither Simms nor Flossie Clements, a 65-year-old Scottsville, Va., resident, knew anything was wrong until the severe pain of PAD hit them.

"My leg and foot were hurting so bad, I couldn't stand it," Clements said. Both women, diagnosed with advanced PAD, had angioplasty performed last year to open the arteries in their legs. The procedure--very similar to the procedure well known for treating blockages in the coronary arteries--is guided by a technique known as digital fluoroscopy or occasionally ultrasound--two ways to display the body's interior vessels and organs. In the angioplasty procedure, a small tube is placed through an incision and into the artery. A balloon is then advanced to the site of the blockage and inflated to compress the buildup against the artery wall, remolding the vessel's shape and creating an adequate pathway, Angle said.

If the artery does not retain its new shape, a miniature wire mesh scaffolding called a stent may be inserted at the blockage site to keep the vessel open. Other treatments can include clot-busting drugs or a bypass graft that creates a detour around the blockage.

There is no guaranteed cure, Angle said, but arresting PAD's progression is critical.

Another approach is gene therapy, which is in the investigational stage in studies by Jeffrey Isner, professor of medicine and pathology at Tufts University School of Medicine and chief of cardiovascular research at St. Elizabeth's Medical Center, both in Boston.

Isner described his first patient in which gene therapy helped create new blood vessels in the August 1996 issue of the Lancet. In that case, DNA was injected into muscles in the patient's legs, where it instructed existing blood vessel cells to generate new vessels.

Isner presented his preliminary findings at the American Heart Association's Scientific Sessions in Orlando in November 1997, where he told the story of a 39-year-old woman who joined the study with severe atherosclerosis in both legs. "The front half of one foot was already black due to onset of gangrene," Isner said. "When she came to us, she was facing two lower limb amputations."

Gene therapy was used in both legs, halting the progression of PAD in one. The other limb was too far gone. "Without this therapy, she would have been a double amputee," he said. There also were patients in the study who did not respond to the treatment, Isner said. He hopes that more answers will be available as a second study continues.

Robert Vogelzang, chief of vascular and interventional radiology at Northwestern University Medical School in Chicago, said his institution will begin similar studies using Isner's findings. "This is the missing piece to the puzzle," he said. "It unequivocally offers great promise."

As for Simms and Clements, they're just glad to get their legs moving and their hands back into the soil.

"Honey, I raked up seven wheelbarrows of acorns the day after I came home," Clements said of the September angioplasty that got the blood flowing in her legs again. "I just rested my leg the next day."

Balloon Angioplasty

Peripheral artereal disease usually starts with the formation of fatty plaque on the artery walls. It's treated by guiding a balloon catheter into the artery and then inflating the balloon to open the artery.

1. A hollow needle is inserted into the femoral artery. Using X-ray imaging, a guide wire is pushed through the needle toward the constricted blood vessel.

2. A balloon-tipped catheter is then threaded over the guide wire to the blocked area. The balloon is inflated and deflated a few times to widen the area, then withdrawn.

SOURCE: The Merck Manual of Medical Information Home Edition and the American Medical Association Encyclopedia of Medicine; Random House