So what exactly is cardiac arrest?

We've expanded our information on cardiac arrest on our website after the death of singer Michael Jackson at the age of 50. He had reportedly suffered one at his home in Los Angeles.

There's often some confusion between cardiac arrest and a heart attack, but they are actually different things.

Cardiac arrest, which is when the heart stops pumping blood around the body because of a disturbance in the normal heart rhythm, can happen without any existing heart condition.

A heart attack can be one of the causes of cardiac arrest, but other causes can include such things as electrocution, bleeding, choking or a drugs overdose.

To find out more about cardiac arrest and heart attack please visit our website

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Our Doubt Kills campaign gets a third wave

Our award-winning Doubt Kills campaign - which first ran in 2006 and again last summer - is currently enjoying a month-long reprise on the billboards, tube posters and bus sides of London.

As the majority of our users are based outside London, we nevertheless thought it a good opportunity to remind you of the core message of Doubt Kills, which is this: If you experience chest pain, call 999 immediately.

You can read more about this message, and hear from people whose lives have been saved by the campaign, on our special Doubt Kills website

There's also a free Doubt Kills podcast, an animation of what happens to your heart during a heart attack, plus an informative interactive quiz - and much more besides.