Sudden Arrhythmic Death Syndrome is when the heart suddenly stops, but at the autopsy, nothing can be found to be wrong.
The heart is controlled by electrical impulses. If these go wrong, you can have an abnormal heart rhythm. If this rhythm is very wrong, it can cause the heart to stop – but because the electrical impulse can’t be measured after death, there is no sign that there was anything wrong with the heart when the pathologist performs the post-mortem.
About 500 people in the UK die every year from Sudden Arrhythmic Death Syndrome.