British heart patients are taking part in a trial which researchers hope will help clear the next hurdle in the race to find the best way of repairing their damaged organs.

Cells from their legs are being injected into their hearts to discover whether cardiac muscle can be prompted to grow new cells. It may offer an alternative to the use of stem or parent cells, which is also of unproved reliability.

This technique too involves harvesting cells, multiplying them in the laboratory and returning them to a different part of the body, but those conducting the trials think it may provide a better solution.

The cells involved here are myoblasts, which will develop into muscle cells. Stem cells have the potential to develop into many types of cell.

The trials began in France and the first patient in Britain underwent the operation at the Heart Hospital, part of University College London, last week. He is said to be "fine", although it is far too early to ascertain the long-term success.

William McKenna, who is heading the British arm of the international trial, which will eventually involve about 300 patients, said: "If we are able to reverse the damage done to cardiac muscle following a heart attack or to safely halt a patient's further progression to heart failure, this would be a revolutionary advance in the treatment of heart disease."

The use of precursor muscle cells and stem cells were two different approaches, Prof McKenna said. Using myoblasts might be a better, since they were being injected into their more natural environment.

It used to be thought that human heart muscle cells did not regenerate in the same way as those in other parts of the body, including the skin and liver. But that orthodoxy has been challenged by recent techniques.

Although it is early days, hope is rising that scientists may be eventually able to reverse at least some types of heart disease, especially disorders of the muscle itself.

Up to 70 Britons below the age of 75 will take part in the trial, which involves three other hospitals: King's College in London, Papworth in Cambridge and Southampton general.

Those involved have all suffered a heart attack and need a coronary heart bypass operation anyway.

The additional injection to the scar tissue of dead muscle adds an extra 20 minutes to the common procedure.

Some volunteers will have cells multiplied in the lab over three weeks from 6g of tissue taken from their legs.

These people will be divided into two groups, each receiving a different amount. A third group will simply receive a saline solution.

All three will be checked by ultrasound at six months and a year to see if damaged or dead muscle has regenerated.

If the technique is successful further trials will be needed to assess the best way of putting the cells into the heart. They are likely to include injection into the heart.

The work is funded by MG Biotherapeutics, a joint venture of two companies, Medtronic and the Genzyme Corporation. It thinks the technique is safer, further along in clinical studies and closer to the commercial market place than that using any form of stem cells.