Lack of aggressive treatment for clogged leg blood vessels means missed heart attack prevention opportunity

Nov 15 2005

Despite the fact that clogged arteries in the legs usually mean clogged arteries near the heart, doctors often fail to give heart-protecting drugs to people with severe leg blood vessel blockages, a new University of Michigan-led study finds.

This lack of preventive care in such patients, who are at high risk for a heart attack or stroke, means that more effort is needed to improve the way doctors and patients deal with an often body-wide problem of clogged blood vessels, the researchers say.

In a presentation at the American Heart Association's annual Scientific Sessions, U-M Cardiovascular Center researchers will show data on 553 patients who came to five Michigan hospitals for procedures to re-open clogged blood vessels in their legs and abdomens. Such blockages are called peripheral artery disease or PAD.

The study shows that among such patients, those who also had a history of heart problems were more likely to receive drugs to lower their cholesterol and blood pressure, compared with those who hadn't had heart problems.

"Patients who have severe PAD but haven't experienced heart-related problems are under-treated when it comes to medical therapy, especially statin drugs to lower cholesterol," says senior author P. Michael Grossman, M.D., an assistant professor of cardiovascular medicine who leads the project that produced the new data. "This is despite the fact that national guidelines recommend physicians treat PAD with the same aggressive medical treatment as they treat coronary artery disease."

The patients in the study were all having procedures called peripheral vascular interventions or PVIs, which are nearly identical to angioplasty and stenting procedures performed in blocked or narrowed heart arteries. PVIs are performed on hundreds of thousands of Americans each year, to open blocked arteries in the legs and abdomen that cause disabling leg pain or kidney problems.

Millions more Americans have less-severe blockages, which still put them at higher risk for heart attack and stroke even if they haven't had a history of heart problems. As many as 20 percent of adults may have PAD, but most don't know it -- instead thinking that "old age" is making their legs hurt or feel weak when they walk or rest.

Once diagnosed, the first treatment for PAD patients is to exercise, lose weight and stop smoking -- the same actions that are known to help their hearts. But medicines such as blood thinners, cholesterol drugs, ACE inhibitors and beta blockers, and procedures such as PVI, are used when lifestyle changes don't do enough.

Other treatments are currently being developed, including experimental approaches that use gene therapy or other biological agents to try to encourage the growth of new blood vessels that could take over for blocked vessels.

At the AHA meeting, Grossman will also present results from a multicenter clinical trial he co-led with sponsorship from a company called Valentis. The trial, which compared a pair of Valentis products against one of the products alone, did not show a difference between the two groups of patients with severe leg pain from PAD in terms of the amount of time they could tolerate walking on a treadmill 180 days after treatment.

But the study did show that both groups improved about 34 to 37 percent, including those who had only received a molecule called a poloxamer that may help repair tissue and reduce inflammation. The other group received the poloxamer together with an injected gene for a protein that stimulates blood vessel growth. Now, Grossman leads a trial at U-M comparing poloxamer against placebo.

Other research on agents that might encourage vessel growth is under way or will be soon at the U-M Cardiovascular Center. In the meantime, the PVI project continues to track current treatment.

Grossman notes that the multi-hospital PVI registry that produced the new data is giving him and other researchers a new way to look at how patients with severe PAD are treated -- before, during and after their artery-opening procedures. It also surveys patients on their quality of life.

The registry, based at U-M, pools data from all the hospitals, and allows researchers to analyze trends and patterns across large groups of patients -- and to look at how well doctors are following national guidelines on PAD treatment. Eight hospitals, including one in Minnesota, have joined the registry, which now includes data on more than 1,000 patients for the entire year following their PVI.

"For the first time, we have a unique opportunity to track how these patients do, and ask important questions about their treatment and its relation to their health, using data from multiple hospitals, and physicians from multiple specialties," says Grossman. He explains that PVI procedures, which are minimally invasive, can be done by specially trained cardiologists, specially trained radiologists, and by vascular surgeons, who also perform open operations called bypasses on PAD patients.

The data are being presented at AHA by U-M cardiology fellow Noah Jones, M.D. They come from patients treated with PVI between 2002 and 2005 at U-M and four other hospitals. Of the 553 patients, 405 had a history of heart attack, chest pain, angioplasty or stenting on their heart arteries, or heart bypass surgery. The other 148 had no history of heart-related problems and procedures.

Before their PVI procedure, 91 percent of the heart patients were taking blood-thinning drugs such as aspirin or clopidogrel to prevent the formation of dangerous clots, compared with 83 percent of patients with no heart history. An even larger gap in statin use was seen: 65 percent compared with 51 percent of non-heart patients. And beta blockers, which lower blood pressure and heart rate, were used in 62 percent of heart patients, compared with only 42 percent of non-heart patients.

These differences narrowed a bit once the patients had had their PVIs and were recuperating in the hospital. But a month after the patients went home, the gap widened again -- suggesting that the patients with no history of heart disease weren't sticking to their medication regimens and that their doctors could do a better job of monitoring and encouraging their use of the drugs.

"The majority of patients with PAD die from heart attacks, heart failure or strokes, so we need to help as many patients as possible get screened, understand their risk, change their lifestyle and receive treatment that's in line with national guidelines," says Grossman.