More than eight million older Americans have a condition that can cause leg pain when they walk even short distances. Yet half of those who have the condition don’t know it and consequently don’t get treated for it, putting themselves at risk for a heart attack, stroke or worse.
The condition, called peripheral artery disease, or P.A.D., is marked by diseased or blocked arteries in the legs. More than half of those with such circulatory problems in the extremities also have coronary or cerebral artery disease, noted Dr. Iftikhar J. Kullo, a cardiovascular specialist at the Mayo Clinic, in The New England Journal of Medicine in March. Failure to diagnose and treat blocked arteries elsewhere in the body can result in more serious, or even fatal, problems if they affect the heart or brain.
It may seem odd that people who have serious difficulty walking normal distances would not know something is wrong and get checked out. Yet, as Dr. Kullo noted, P.A.D. is both underdiagnosed and undertreated. And the number of cases of P.A.D. is only likely to rise as the population ages, he said.
“A lot of people limit their activity for other reasons, like a hip problem, back pain or breathing difficulty, and may not push themselves hard enough to provoke symptoms of P.A.D.,” said Dr. Paul W. Wennberg, a cardiologist and specialist in vascular disease at the Mayo Clinic. Or they may think their limited ability to exercise is to be expected, given their advancing years. Still others, Dr. Wennberg said, “may have only minimal disease in their legs, or they adapt their lifestyle to where they don’t notice symptoms anymore.”
In other words, since walking brings on pain, people typically find myriad ways to avoid doing it.
But this very response — remaining sedentary — is counterproductive, Dr. Wennberg said, because the best treatment for P.A.D. is exercise: Walking up to the point of pain, then resting until the pain subsides, then walking again, repeating the sequence until you’ve walked for 20 to 30 minutes (not counting rests) every day.
With this approach, Dr. Wennberg explained, exercise tolerance gradually increases as collateral blood vessels form in the legs that can compensate for blockages in the main arteries.
Just as teachers often have star pupils, Dr. Wennberg talks fondly of a man who was his star patient. When first seen, the patient, a 76-year-old Minnesotan, was afflicted with such severe peripheral artery disease that he couldn’t walk much beyond his backyard. Although a nonsmoker, the man had chronic obstructive pulmonary disease, which also limited how far he could walk. Yet he desperately wanted to be able to hike the nature trail behind his house, which motivated him to follow the doctor’s prescription religiously: Walk until it hurts, rest, then walk some more. Repeat several times a day.
“He got a treadmill to use in his house, and he walked outside whenever he could,” Dr. Wennberg recalled. “In just three months, he had doubled his walking distance as measured on a treadmill in the lab, and before long he was able to walk the mile-long nature trail.” Not only did the exercise prescription reduce his leg pain, it also improved his breathing. Together, these benefits enabled him to walk the desired distance without pain or fatigue.
Another of Dr. Wennberg’s patients, Donovan Merseth, 76, of Zumbrota, Minn., said he walks his two dogs four or five times a day, accumulating daily walks of three to four miles. “The more active I am, the better I feel,” Mr. Merseth said in an interview. “I walk at a moderate pace,” he said, calling his exercise “a senior power walk.”
Variable symptoms present another stumbling block to getting a correct diagnosis of P.A.D. The discomfort P.A.D. causes “is more often atypical than typical,” Dr. Wennberg wrote in the journalCirculation. “Descriptions such as ‘tired,’ ‘giving way,’ ‘sore,’ and ‘hurts’ are offered more often than ‘cramp’,” which can challenge an examining physician’s ability to suspect P.A.D. as the cause of a patient’s discomfort.
He suggested that doctors ask, “What’s the most strenuous thing you do in a typical week? Do you do any routine exercise, like walking? Do you get pain when you walk?”
A simple noninvasive test that can be done in any doctor’s office, called the ankle-brachial index, or ABI, test, can reveal the likelihood of P.A.D. The test, which takes only a few minutes, compares blood pressure measured at the ankle with blood pressure measured in the arm. Lower pressure in the leg is an indication of P.A.D.
The index is calculated by dividing the systolic (top number) blood pressure in the arteries near the ankles by the systolic blood pressure in the arms. A low number strongly suggests a narrowing or blockage in the arteries that supply blood to the legs.
Follow-up tests, like an ultrasound exam of the arteries to the brain, may be done as well. “If there’s blockage in one area of the body, it’s likely also to be in another,” Dr. Wennberg noted.
Not surprisingly, the risk factors for P.A.D. closely match those for coronary heart disease: smoking (currently or formerly), diabetes, high blood pressure and high cholesterol. Consider asking your doctor to do the ABI test if you are 50 or older and have any of the above risk factors, even if you haven’t yet noticed a problem with walking (though insurance may not cover the cost if you lack symptoms).
However, Dr. Wennberg wrote, the ABI test done during rest may miss peripheral artery disease in nearly one-third of patients; they may require an ABI test following exercise on a treadmill to reveal the problem. The blood pressure measurements must be taken within a minute of stopping the exercise.
Given the same risk factors, African-Americans are more likely than Caucasians to develop P.A.D.
The average age at which people develop P.A.D. is 70, Dr. Wennberg said, adding that it occurs a decade earlier in people with diabetes and even earlier in people who both smoke and have diabetes.
Smoking increases the risk of developing P.A.D. fourfold, and more than 80 percent of people with the condition are current or former smokers.