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.

Sykehuset Telemark performs every year approximately 800 Holter ECG examinations. Approximately 200 of these are on the indications tachycardia, and in about 170 patients the examination does not discover any tachycardia Patients who were examined in the period from August 1. 2004 to November 1. 2005 with a negative Holter are mailed a letter with information of the min invasive electrophysiological examination, and an offer of volunteer participation. Patients given their informed consent are then according to waiting list called for the mini-invasive EP-study.

The protocol of the EP stimulation consists of: determination of pacing threshold, pacing with 8 asynchronous beats 600ms and an extrasystole with decremental intervals from 550 ms to 200 ms. The seri is repeated with pacing on 400ms and with two extrasystoles as well as with isoprenaline stimulation.

Inclusion Criteria:

• History of complains of tachycardia
• No arrythmias detected by a 24 hours Holter ECG
• Age 19 to 74 years

Exclusion Criteria:

• Patients younger than 18 years
• Patients older than 75