The study, backed by the European Commission, will involve 3000 patients in 11 European countries, and will show for certain whether stem cell treatment is effective in treating heart conditions.
The trial will provide all patients with standard treatment to widen their narrowed arteries by inserting a small tube called a stent.
Half of the patients will also have stem cells taken from their bone marrow and injected into their heart within days of them suffering a heart attack.
"It's come from yourself to mend yourself - it's not something I ever thought would be possible but it's fantastic," said 54-year-old Neal Granger.
The first to be treated in the UK, Mr Granger had his bone marrow stem cells injected into his heart just days after his heart attack last month.
He will be monitored for the next five years and will need to keep a close eye on lifetstyle factors such as diet and exercise.
Cardiovascular disease remains UK's biggest killer, accounting for more than 161,000 deaths each year.
