Stem cells from heart attack patients helped improve blood-pumping ability and restore vitality in cardiac muscle, according to a small trial.
It is the first time patients have been given an infusion of their own cardiac stem cells in the aim of solving the impact of heart failure rather than simply treating the symptoms of it.
The findings are so promising that the study's chief investigator said a potential "revolution" was in the offing if larger trials succeeded.
Stem cells are infant cells that develop into the specialised tissues of the body.
They have sparked great excitement as they offer hopes of rebuilding organs damaged by disease or accident.
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The new study, published online in The Lancet on Monday, tested cardiac stem cells on 16 patients who had been left gravely ill as a result of an acute myocardial infarction.
The index used for cardiac health is called the left ventricular ejection fraction (LVFV), which calculates the capacity of the left ventricle to expel blood in the space of a heartbeat.
For a person in normal health, the LVFV is 50 per cent or higher.
Among the study patients, though, this had fallen to 40 per cent or lower. At such a threshold, shortness of breath and fatigue are chronic and often disabling.
The stem cells were isolated from a coronary artery that had been removed when the patients underwent a coronary bypass.
Within four months of treatment, the LVFV rose by 8.5 per cent and after a year by 12 per cent - four times what the researchers had expected.
Scans of the patients' hearts also showed a reduction in the area of tissue that had been scarred by the infarction, a discovery that challenges conventional belief that once scarring occurs, heart tissue is permanently dead.
The volunteers also reported a substantial improvement in quality of life, and there were no significant side effects.
Seven patients with similar heart problems were enrolled as "controls", to serve as a comparison. There was no change in their LVFV, in scar tissue or in their quality of life.
"The results are striking," said lead investigator Roberto Bolli of the University of Louisville, Kentucky.
"While we do not know why the improvement occurs, we have no doubt now that (LVFV) 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."
The team is seeking funding to launch a larger, or Phase II, trial - the second in the normal three-phase process of assessing a new treatment for safety and effectiveness.
Previous stem-cell work on heart damage has used cells harvested from bone marrow.
The interest in cardiac stem cells is that they are self-renewing, produce daughter cells and differentiate into all types of cells in the heart.
The results were presented concurrently at a meeting of the American Heart Association in Orlando, Florida.
