Patients with advanced heart disease who received an experimental stem cell therapy showed slight improvements in blood pumping but no change in most of their symptoms, US researchers said Saturday.
Study authors described the trial as the largest to date to examine stem cell therapy as a route to repairing the heart in patients with chronic ischemic heart disease and left ventricular dysfunction.
Previous studies have established that the approach is safe in human patients, but none had examined how well it worked on a variety of heart ailments.
The clinical trial involved 92 patients, with an average age of 63, who were picked at random to get either a placebo or a series of injections of their own stem cells, taken from their bone marrow, into damaged areas of their hearts.
The patients -- 82 of whom were men -- all had chronic heart disease, along with either heart failure or angina or both, and their left ventricles were pumping at less than 45 percent of capacity.
None of the participants in the study were eligible for revascularization surgery, such as coronary bypass to restore blood flow, because their heart disease was so advanced.
Those who received the stem cell therapy saw a small but significant boost in the heart's ability to pump blood, measuring the increase from the heart's main pumping chamber at 2.7 percent more than placebo patients.
The treatment worked best in the youngest patients, those under 62, according to the analysis which was done after six months of treatment.
However, other factors showed no improvement -- the heart's maximum oxygen consumption did not change and the defects in the heart were not healed by the treatment -- according to an analysis of the study in the Journal of the American Medical Association.
"This is the kind of information we need in order to move forward with the clinical use of stem cell therapy," said lead investigator Emerson Perin, director of clinical research for cardiovascular medicine at the Texas Heart Institute.
Perin's research, which was conducted between 2009 and 2011 across five US sites, was presented at the annual American College of Cardiology Conference in Chicago.
The technique involved taking bone marrow samples from the patients and processing the marrow to extract stem cells. Doctors then injected the cells via catheter into the heart's left ventricle.
The injections, comprising some 100 million stem cells in all, were specifically targeted at damaged areas, identified by real-time electromechanical mapping of the heart.
"With this mapping procedure, we have a roadmap to the heart muscle," said Perin in a statement released ahead of the presentation in Chicago.
"We're very careful about where we inject the cells; electromechanical mapping allows us to target the cell injections to viable areas of the heart," he added, describing the procedure as "relatively quick and painless."
Heart disease is the leading killer in the United States, claiming nearly 600,000 lives per year, according to the US Centers for Disease Control and Prevention.