Firstly call 9-1-1 immediately — the sooner you contact emergency personnel, the less damage a person’s heart can sustain. It is not advised that you drive someone to a hospital considering that EMTs can begin life-saving treatments on the way to the emergency room. If he is at a considerable risk, it might be appropriate to keep an external oxygen tank, aspirin, or even nitroglycerin around in case of an emergency, however allow the professionals to do what they can. We hope you never have to encounter this, but it can help to be prepared!