Heart palpitations at any time of the day can generate concern in a patient, but they are particularly worrying when a person experiences them at night. The causes of the problem can be really varied - sometimes palpitations are a manifestation of a heart rhythm disturbance, and sometimes they are a consequence of the use of some stimulants, sports or the experience of severe stress. So when should palpitations at night be a cause for concern and a reason to visit the doctor?