Catheter ablation has proven to be an effective treatment option in patients suffering from symptomatic persistent atrial fibrillation (AF). Catheter ablation consists of two major steps: (1) Isolation of pulmonary veins to abolish the trigger of atrial fibrillation and (2) modification of left atrial and eventually right atrial substrate by ablation of complex fractionated atrial electrograms (CFAE). CFAE are mainly found at the ostia of the pulmonary veins, around the left atrial appendage, at the mitral annulus and the septum.

When ablating CFAE 40-65% of the patients show a regularization of AF to an atrial tachycardia (AT) that can be macro- or micro-reentrant (localized re-entry). Until now the significance of the AT is unclear.

In the following study we examine the hypothesis that an ablation of AT occuring during CFAE ablation (group 1) significantly improves outcome defined as freedom of atrial arrhythmia (AF or AT) compared to patients that are cardioverted when AF has regularized to AT (group 2).

Inclusion Criteria:

• Patients (>=18 und < 80 years) with symptomatic persistent AF (AF episode enduring at least 7 days) but are successfully convertable in sinus rhythm (SR).
• At least one unsuccessful attempt of antiarrhythmic drug (betablocker or class I oder III).
• Oral anticoagulation with phenprocoumone or warfarine for at least 4 weeks prior to ablation with weekly documented INR > 2..
• Withdrawal of antiarrhythmic drugs at least 3 half times prior to ablation except amiodarone.
• Atrial tachycardia occurring during ablation of CFAE (defined as CL > 200 msec und stable activation sequence).

Exclusion Criteria:

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