Doctors are to treat heart attack patients with stem cells taken from their own bone marrow in a pioneering attempt to prevent suffering.
The 50 patients will have the stem cells injected into their hearts within the critical five hours after suffering a heart attack.
At the same time they will undergo emergency angioplasty, a procedure to open up blocked arteries.
Their progress will be compared with 50 patients given a "dummy" injection not containing stem cells.
Stem cells are immature cells with the potential to develop into different kinds of tissue. Those from the bone marrow have shown to have the ability to repair heart muscle and grow blood vessels.
The research project, the first to be supported by the UK Stem Cell Foundation, is aimed at delaying or preventing the onset of heart failure.
This occurs when the heart muscle is damaged and weakened. It is a frequent complication of heart attacks which can lead to a serious deterioration in quality of life, and sometimes death.
Patients brought to the London Chest Hospital and H eart Hospital will be recruited for the study.
Dr Anthony Mathur, consultant cardiologist at the London Chest Hospital, said: "If we can demonstrate improvement in the quality of life of patients, then this will be a significant step forward in the treatment of heart disease.
"Because the stem cells are taken from the patient themselves, there are minimal ethical issues surrounding this procedure. There is also less likelihood of rejection complications."
Several small studies throughout Europe have demonstrated that an infusion can lead to improved heart function after a heart attack.
Professor Peter Weissberg, medical director of the British Heart Foundation, said: "In the future, stem cells could herald a new frontier for heart patients. We welcome research that helps us understand the potential role stem cells may yet play in treating heart disease and hope that this study will complement the BHF's existing research in this area."