• Cinical arrhythmia is fairly documented AF, pulmonary vein isolation will be performed. If AF persists after this step, electrical cardioversion will be performed.
• If clinical arrhythmia is fairly documented type 1 AFL, cavo-tricuspid isthmus ablation will be performed.
• If clinical arrhythmia is AT, it will be induced (if not persistent), identified by means of activation and/or entrainment mapping, and ablated.
• If clinical arrhythmia is AT that is non-inducible during EP study, no ablation will be done.
• If other incidental (or induced) AT is observed that can be qualified as non-clinical it will not be targeted unless considered important to ablate at discretion of operator.
• No induction protocols for other, on top of already ablated, arrhythmias will be attempted.

- The initial ablation steps will be identical to those in patients from Group A.

Supplemental ablation will consist of:

• Empirical lesion set within right atrium: superior vena cava isolation, posteroseptal bicaval line, and cavo-tricuspid isthmus ablation (if not already ablated)

AND

• Homogenization of low-voltage zones (if any) in left / right atrium defined by bipolar voltage <0.5 mV in sinus rhythm or <0.2 mV in AF / AT. The threshold can be adapted in severely diseased atria to delineate reasonably smaller zones (<20% of atrial surface) achievable to ablate.
• Arrhythmia induction protocol by10-second burst atrial pacing with cycle length of 300 ms decremented by 10 ms up to atrial refractoriness or cycle length of 200 ms.
• Inducible ATs will be mapped and ablated if feasible. In case of inducible persistent (>5 min) AF, pulmonary vein isolation will be performed if not previously done as per protocol.

Catheter ablation of atrial fibrillation or atrial tachykardie related to atrial fibrillation with use of radiofrequency energy.

Documented arrhythmia recurrence >30 s without antiarrhythmic drugs in post-blanking period after the index ablation

Documented on-drugs arrhythmia recurrence

Symptoms of arrhythmia by questionare