It's one of the biggest killers in the UK. Every year, seventy-six thousand people die following a heart attack.
But many of these deaths could be avoided if the public was more aware of the life-saving equipment that's in our village halls, gyms and work-places.
That's the view of South Central Ambulance Service who're raising awareness of difibrillators in a new campaign.
They want more of us to know how to use them and feel confident in doing so. Juliette Fletcher reports from Wantage on the life-saving technology that we can all use.