ASDA has agreed to introduce defibrillators - which shock the heart - into every store alongside staff trained in life-saving CPR.
An agreement between the British Heart Foundation (BHF) and the retailer will see defibrillators in all 609 Asda stores and offices by the end of the year.
It is hoped the move will significantly increase survival rates for people suffering a cardiac arrest out of hospital, with survival rates currently at about 10%.
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A defibrillator can be used by any member of the public to deliver an electric shock to the heart when someone is having a cardiac arrest and could boost this number significantly.
The BHF estimates that 60,000 cardiac arrests occur out of hospital every year across the UK. A cardiac arrest is commonly caused when a person has a problem with their heart.
Once the defibrillator box is opened, a recorded voice gives easy instructions on where to place pads on a person's chest. Users then simply press a large button to start electrical shocks to the person's heart.
The defibrillator will not work unless the person is having a cardiac arrest.
Dawn Clements, Asda's head of community, said: "The commitment we're making today could cut the amount of time a cardiac arrest sufferer has to wait for life-saving defibrillation."
Research has shown that when somebody is having a cardiac arrest, every minute of delay in resuscitation and defibrillation reduces their chance of survival by 10%.
BHF chief executive Simon Gillespie said cardiac arrest survival rates in the UK were "astonishingly low" compared to other countries.
He added: "Asda's bold commitment to become the first large retailer to have CPR-trained staff and public access defibrillators in every store will be instrumental in helping communities up and down the country access the life-saving support they need in an emergency."