Palpitations are the name for a sensation where you feel that your heart beat is abnormal – sometimes for only short periods of time (seconds or minutes), sometimes for long periods of time (hours). Palpitations can be due to problems with the heart; they can be due anxiety or nervousness; and they can be due to a combination. Sometimes palpitations are exacerbated by caffeine and alcohol
causing palpitations are abnormal heart rhythms, either transient or continuous. For example atrial fibrillation, ectopic beats, inappropriate sinus tachycardia.
often required after a blackout are: ECG, echocardiogram (ultrasound scan of the heart) and 24 hour heart rhythm monitoring (achieved by wearing a small monitor for a day).