LONDON (AP) _ Medication that prompts the growth of new blood vessels may one day help the body produce its own bypasses around clogged heart or leg arteries, a new study suggests.
Researchers have been experimenting with substances that stimulate blood vessel growth for nearly a decade, but a landmark study published this week is the first demonstration such substances can make patients better.
The research doesn't prove people with painfully blocked leg arteries grew new vessels, but experts say their endurance in treadmill tests was a strong indication of a beneficial effect.
``This is hopeful, but it needs further work,'' said Ira Herman, a professor of physiology at Tufts University who researches the growth of blood vessels, a process called angiogenesis. ``While they've done blood flow measurements, that doesn't necessarily convince me that angiogenesis accounts for that improved blood flow.''
Experts believe the body probably makes its own bypass blood vessels to get around blocked vessels and suspect that this rescue process does not work well in those people who have heart attacks or major blockages that need surgery.
The growth of new blood vessels is stimulated by a protein called fibroblast growth factor, or FGF-2. The researchers used a genetically engineered copy of the protein in the study.
``Therapeutic angiogenesis has the potential to truly revolutionize our therapies,'' said one of the study's investigators, Dr. Brian Annex, director of the angiogenesis research center at Duke University Medical Center. ``We're not there yet, but this is a major step forward in advancing a very exciting field.''
One concern is the treatment might foster unwanted, or disease-related, blood vessel growth, perhaps causing cancer to progress.
The study, published this week in The Lancet medical journal, involved 174 patients with clogged leg arteries, a condition called peripheral artery disease. All the patients had intermittent cramp-like pain in their calves, a feature that doctors call claudication.
The pain of claudication is equivalent to that of angina in people with coronary artery disease.
After taking a treadmill walking test, the patients were divided into three groups. One group got an injection of the protein into the main leg artery on day one and another shot of the drug a month later. The second group got the injection on day one and a dummy injection a month later, while the comparison group got fake injections both times.
Three months after the first injection, those who got the fake injection lasted 0.6 minutes longer on the treadmill than they did during the initial test, while those who got the drug on the first day stayed on the machine 1.77 minutes longer than they had on the first day. Those who got a second dose of the drug did no better than those who only got one dose.
``The improvement on the treadmill looks modest, but it probably underestimates the effect of the treatment on everyday functions in patients,'' said Dr. Richard Donnelly, a professor of vascular medicine at the University of Nottingham, who wrote an independent critique of the work for the journal.
``What does that mean when you're walking with your shopping on a street? We actually don't know,'' he said. ``But there are lots of data in angina where the effect on the treadmill was modest but the effect on quality of life was quite significant.''
Dr. Valentin Fuster, director of the Cardiovascular Institute at Mount Sinai Medical School in New York and former president of the American Heart Association, said he did not think the impact on the patients' quality of life was great.
``It didn't make a difference to the onset of claudication (pain),'' noted Fuster, who was not connected with the study. ``They could walk a little further, but the pain still began at the same time, regardless whether they used the drug or not.''
Also, it is unclear whether an exercise program or the drug cilostazol, both existing treatments for the disease, would have helped these patients or how well the protein injection would have performed in comparison, Fuster said.