How fast can the heart beat?

Question: How fast can the heart beat?
- Keywords:
  beat,
  fast,
  heart
Asked by claire to Eoin on 25 Feb 2018. This question was also asked by christiano.
- Eoin McEvoy answered on 25 Feb 2018:
  
  Normally the heart beats around once every second. During high intensity exercise, like sprinting, some people’s hearts beat up to 4 times a second!

Question: How fast can the heart beat?