If someone has become unresponsive and they are not breathing normally, they could be in cardiac arrest. Find out what to look for and what to do, including how to do CPR and using a defibrillator.

A heart attack happens when the supply of blood to part of the heart is suddenly blocked, usually by a blood clot. Find out what to look for and what to do.

Angina is pain in the chest, which can happen with increased exertion or excitement. Find out what to look for and what to do.