Doctors at a London hospital have started treating heart attack patients with their own stem cells in the largest trial of its kind ever undertaken.

The patients at the London Chest Hospital are among the first of 3,000 participants in a Europe-wide study looking at the life-prolonging potential of stem cell therapy.

All will be treated within five days of suffering a heart attack. Stem cells taken from bone marrow will be injected into their hearts in the hope of increasing survival rates by a quarter.

The European Commission has contributed £4.8 million to the BAMI trial taking place in 10 European countries.

It follows the “Regenerate” series of three smaller charity-funded studies led by Barts Health NHS Trust consultant cardiologist Anthony Mathur.

“The BAMI study is the biggest and most comprehensive trial of its kind in the world and follows the successful Regenerate trials,” said chief trial coordinator Mathur.

“It has taken two years to get to the point where we are ready to accept patients, but we have now reached that stage and we are all very excited.

“Our studies will tell us if adult stem cells from bone marrow can repair damaged hearts and, if so, how these cells should be administered to patients.”

Co-researcher John Martin, from University College London, said: “This trial brings together a powerful partnership of European doctors and scientists to solve a fundamental problem of importance to all people. It will give an answer about whether adult multi-potential stem cells in their natural environment can treat human disease.”

Stem cells are immature “mother” cells capable of developing into different tissue types.

Bone marrow contains two kinds of adult stem cells that can differentiate into a range of cell types including heart muscle cells and blood cells.