Sometimes people don’t experience many signs and symptoms, but the main symptoms of familial arrhythmia are: palpitations fainting or blackouts (also known as syncope or "near" faint) The majority of children and young adults with syncope have a normal heart disease and no major heart rhythm problem. However, it’s really important to speak to your GP or health professional if you - or a member of your family - have suffered unexplained fainting, especially if it's happened more than once.