Northwestern University's Feinberg School of Medicine scientists, in the first such U.S. study, found the transplanted stem cells produced a reduction in angina pain, as well as improved functioning in the patients' daily lives.

Within three to six weeks after the patients were injected with their own stem cells, many who used to experience pain just from walking to the refrigerator, reported only having pain when climbing two flights of stairs, researchers reported.

Lead investigator Dr. Douglas Losordo, director of the Feinberg Cardiovascular Research Institute, said the study is the first human trial in which patients' own purified stem cells were injected into their hearts in an effort to re-grow small blood vessels that constitute the microcirculation of the heart muscle. Researchers believe the loss of such blood vessels contributes to the pain of chronic, severe angina.

The findings are detailed in the current issue of the journal Circulation.