Patients complaining of tachycardia but with a negative Holter ECG, are for a limited time period offered a simplified electrophysiological(EP) examination. By a full electrophysiological study(EP study)electrodes are introduced for pacing and sensing i all four heart chambers. Where as by the mini invasive EP study only one electrode is introduced to the right atrium. The simplified procedure represent a smaller risk of complications, requires less resources but should yield the same diagnoses in more than 90% of the cases. The study is a feasibility study to see if the procedure can discover arrythmias in a fairly unselected patient population.