The study was presented by Dr. Douglas Losordo, principal investigator of the study and director of the Feinberg Cardiovascular Research Institute, at the American College of Cardiology's 58th annual scientific session March 28.
Heart disease is an umbrella term that includes a number of problems influencing the normal functioning of the heart. A typical characteristic of the disease is the occlusion of the coronary arteries, which diminishes the supply of blood to the heart, said Muthu Vaduganathan, a first-year graduate student at Feinberg.
Injecting stem cells into certain parts of the heart muscle deprived of regular blood supply increased exercise capacity, reduced chest-pain episodes and improved overall blood flow in the heart, Losordo said.
The research was based on a finding made 10 years ago about a white blood stem cell observed to have the capability of differentiating into the cells that make up blood vessels - the small "conduits" that carry blood to various parts of the body.
"This finding opened up the possibility that the building blocks for creating a vascular supply were in our bloodstream," Losordo said.
Researchers have spent the past 10 years testing the effects of the stem cell on both the laboratory bench and in animal models before testing on humans.
The stem cell therapy was administered to 167 patients with advanced stages of heart disease who had already exhausted conventional methods, such as angioplasty and heart bypass surgery, said Dr. Charles Davidson, chief of the Cardiac Catheterization Laboratories at Northwestern Memorial Hospital.
"These patients continued to have severe symptoms despite the best treatment we have available," he said. "(Using stem cells) is not meant to be cheaper, it's not meant to be quicker - it's meant to offer hope for people who don't have conventional options."
Despite early promise shown in clinical trials, more research needs to be done to better determine the safety and long-term effectiveness of the procedure, said Dr. Robert Bonow, chief of the Division of Cardiology at Northwestern Memorial.
"Thus far, we have evidence that the patients are doing better - everything is moving in the right direction," he said. "But we can't be too definite about how long the benefit will continue and whether it will be a long-lasting effect."