In the trial, cardiac stem cells were used to repair the severely damaged hearts of 16 patients. It was the first time this had ever been done in humans.
After one year, the ejection fraction or ''pumping efficiency'' of the hearts of eight patients had improved by more than 12%.
All patients whose progress was followed underwent some level of recovery.
The results tripled the 4% improvement researchers had expected to see.
Although this was an early stage trial and larger studies are needed, scientists believe the promise it shows has huge implications.''The results are striking,'' said Professor Roberto Bolli, one of the research leaders from the University of Louisville in the US. ''While we do not yet know why the improvement occurs, we have no doubt now that ejection fraction increased and scarring decreased.
''If these results hold up in future studies, I believe this could be the biggest revolution in cardiovascular medicine in my lifetime.''
A total of 23 patients took part in the ''Scipio'' trial, all of whom had suffered heart failure due to a previous heart attack. Sixteen were assigned to the stem cell therapy while the other seven received standard care.
Heart failure occurs when a damaged heart is weakened and unable to pump enough blood around the body. It is commonly caused by a heart attack and can lead to serious disability and a shortened life.
The ground-breaking new treatment involved extracting cardiac stem cells (CSCs) - self-renewing cells that rebuild hearts and arteries - from patients during bypass surgery.
The cells were purified and grown in the laboratory before being injected back into damaged regions of the patients' hearts four months later.
A million CSCs were infused into each patient via a balloon catheter, an expandable device used to open up arteries.
Heart pumping efficiency is assessed by measuring the fraction of blood expelled or ''ejected'' from the left ventricle with each beat.
At the start of the study, the patients had an average left ventricular ejection fraction (LVEF) of 40% or lower. Normal LVEF is 50% or higher.
Over a period of four months patients who underwent the treatment saw an 8.5% improvement in LVEF. After one year, this increased to 12.3%. LVEF did not change in the seven ''control'' patients who did not receive the therapy.
The findings were published today in an online edition of The Lancet medical journal. They were also presented at the American Heart Association's Scientific Sessions meeting in Orlando, Florida.
Magnetic Resonance Imaging (MRI) scans conducted on a number of patients showed that scarring in their hearts had been reduced.
The small Phase I study was primarily designed to assess safety rather than effectiveness.
Prof Bolli said his team now intended to apply for funding for a much bigger, multi-centre Phase II trial.
Previous research in animals had suggested that CSC transplantation can overcome the effects of non-hereditary heart failure.
Commenting on the study in The Lancet, Professor Gerd Heusch, from the University School of Medicine in Essen, Germany, wrote: "The results from Scipio raise new optimism because the study is based on rigorous quality standards and the reported benefits are of an unexpected magnitude... we will have to see whether further data will meet the promises of the present study. More patients will need to be followed up over a longer period."
taken from http://www.telegraph.co.uk/health/healthnews/8889031/Stem-cell-test-is-biggest-breakthrough-in-treating-heart-attacks-for-a-generation.html