Cardiac arrhythmia is a condition when the heart develops irregular heartbeats, which are either too fast or too slow. Heart beats are from 50 to 100 per minute. It is harmless in people with normal heart conditions but for those with weak hearts it may lead to heart attacks.
Some fatalities that occur during ship sinking are due to cardiac arrhythmia. When the body comes in contact with cold water the heart suffers highly irregular beatings.