This randomized study compares two energy sources for the catheter based ablation of typical isthmus-dependent atrial flutter: The (standard) radiofrequency (RF) ablation technique and the cryo-ablation technique regarding the acute and long term efficacy and safety.

This randomized study compares two energy sources for the catheter based ablation of typical isthmus-dependent atrial flutter: The (standard) radiofrequency (RF) ablation technique and the cryo-ablation technique. The RF ablation of typical atrial flutter has become a standard approach with very high curing rates and low complication incidence. However, ablation with RF is painful since the underlying cardiac tissue heats up (up to 70-80°C inside the tissue) and especially the target of ablation in typical atrial flutter, the so-called cavo-tricuspid isthmus, is a very pain-receptive area. Cryo-ablation, which destroys tissue by freezing it down to -80 to -90°C, is thought to be less painful or even painless with the same efficacy than RF ablation.

The acute and long term (6 months follow-up, non-invasive) efficacy and safety is the combined endpoint.

Inclusion Criteria:

• age between 18 and 80 years
• documented atrial flutter which is most probably typical isthmus dependent atrial flutter
• informed written consent

Exclusion Criteria:

• prior ablation for atrial flutter
• concomitant arrhythmia which is treated during the same ablation procedure
• prior MAZE operation
• contra indication for catheterization
• physical or psychiatric disorder making participation in the study impossible
• pregnancy
• prior participation in the study
• participation in another study