With mention of A&E and attempts at cardioversion I might have made it sound as though I was in a critical state! That wasn't the case: like seniorcit, I was simply wanting to capture evidence of what was happening when my heart was "palpitating". My first thought was to see my GP, but was concerned that my heart would be behaving normally again by the time I got an appointment. Whilst looking up their phone number on the surgery website I saw mention of the 111 number for non-emergencies, so I rang that and after going through my symptoms they said I should go to A&E. I wasn't prepared for how seriously the hospital responded: I had imagined that they could just do a quick ECG and then let me go, so I hadn't gone prepared for an overnight stay!