Bone marrow stem cell therapy offers "moderate improvement" to heart attack patients, according to a large UK review of clinical trials.
The analysis by the Cochrane Collaboration looked at 33 trials involving more than 1,700 patients.
Currently, the standard treatment for people suffering a heart attack (due to a blockage in the artery supplying blood to the heart) is to directly open the artery with a tiny balloon in a procedure called primary angioplasty and to introduce a small tube into the artery to keep it open called a stent.
The use of primary angioplasty and stents to reopen the blocked artery can lead to a 33% reduction in the mortality (death rate) associated with this condition.
Bone marrow stem/progenitor cells has been investigated as a new treatment that may prevent the damage to heart muscle caused by a heart attack in addition to the treatment offered by primary angioplasty.
Analysis of randomised controlled trials to 2011 indicates that this new treatment may lead to some improvements over standard treatment as measured by tests of heart function in the short and long term.
The report suggested that, while longer term trials are needed, bone marrow therapy "may lead to a moderate long-term improvement" in heart function which "might be clinically very important".
It said there was still no evidence of "any significant effect on mortality" in comparison with standard treatment.
However, this may be due to the size of the studies and that patients were followed for a short period of time.
Lead author Dr Enca Martin-Rendon, from NHS Blood and Transplant at the John Radcliffe Hospital in Oxford, said: "This new treatment may lead to moderate improvement in heart function over standard treatments.
"Stem cell therapy may also reduce the number of patients who later die or suffer from heart failure, but currently there is a lack of statistically significant evidence based on the small number of patients treated so far.
"The review comes very shortly after doctors reported the first case of using heart cells to heal heart attack damage.
Researchers are beginning to show that taking cells from a heart, growing millions of new heart cells in the laboratory and pumping those back into the heart may reduce scar tissue and lead to new heart muscle.
However, the trials are at a very early stage and in only a handful of patients.
Using a similar technique with cells taken from the bone marrow, which is a prime source of stem cells, has a much longer pedigree.
Starting next year, Professor Anthony Mathur, from Barts and the London School of Medicine and Dentistry, is leading the largest ever trial of stem cells in heart attack patients.
Three thousand patients across Europe will take part.
They will be injected with stem cells five days after a heart attack and then followed for two years to see if the therapy affects life expectancy.
SOURCE:http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD006536.pub3/abstract DM, Fisher SA, Brunskill SJ, Doree C, Mathur A, Watt S, Martin-Rendon E.Stem cell treatment for acute myocardial infarction. Cochrane Database of Systematic Reviews 2012, Issue 2