July 7, 2011 -- An experimental therapy involving stem cell injections from the patient's own blood is showing promise in the treatment of people with chest pain that is not responsive to drugs, angioplasty, or surgery.
Results from a pivotal study of the treatment were reported today in the American Heart Association (AHA) journal Circulation Research.
Patients with untreatable angina who received the injections of CD34+ stem cells in key areas of the heart had significantly fewer chest pain episodes and significantly better performance on exercise tests than patients who got placebo injections.
Drugs, angioplasty, and coronary artery bypass graft (CABG) surgery are the main treatments for angina -- chest pain caused by blocked coronary arteries.
About 850,000 Americans have angina that persists despite available treatments.
"These are patients who have been on drugs and may have had multiple angioplasties or CABG surgeries," AHA President Gordon Tomaselli, MD, tells WebMD. "Their activities are severely restricted by their chest pain and right now we have little to offer them."
The new treatment came from the discovery about a decade ago that CD34+ stem cells stimulate the formation of new blood vessels, study researcher Douglas W. Losordo, MD, of Chicago's Northwestern University tells WebMD.
"Coronary artery disease involves not only the blockage of major arteries, but the death of small vessels, or capillaries, of the heart muscle," he says. "This treatment targets these small vessels that have been damaged. The stem cells have shown the ability to repair and replace them in animal models."
The approach also showed promise in a 2007 pilot study involving fewer than 30 patients.
The newly reported study included 167 patients with severe angina treated at 26 medical centers across the country.
Chest Pain Relief
Study participants received one of three treatments: low-dose CD34+ injections, high-dose injections, or placebo.
Patients were given a drug for several days to increase the number of CD34+ stem cells in the blood. Blood was collected and processed to collect the stem cells, and then, using a catheter threaded into the heart, the researchers injected the CD34+ cells into areas of the muscle that had been identified as oxygen-deprived areas. The patients received 10 such injections during a single catheterization procedure.
Among the major findings:
Six months after the procedure, patients treated with the stem cells had an average of seven attacks of angina a week, compared to close to 11 in the placebo group.
At 12 months, the low-dose stem cell patients were having around six chest pain episodes a week, compared to 11 in the placebo-treated patients.
Exercise tolerance test scores were also better in the stem-cell-treated patients. The low-dose stem cell patients had improvements of 139 seconds, compared to 69 seconds in the placebo-treated patients.
Patients in both active treatment portions of the study used less nitroglycerin to treat angina attacks than patients in the placebo group, but the difference was small.
About one in three patients had elevations of a cardiac enzyme that is associated with heart attacks. While the elevations did not appear to be clinically significant, Losordo says the researchers will continue to closely monitor cardiac enzymes in patients who receive the treatment.