Electrophysiologic study and radiofrequency catheter ablation of isthmus-independent atrial flutter.

We report the electrophysiologic study and radiofrequency catheter ablation of isthmus-independent atrial flutter in 2 patients. The isthmus-independent atrial flutter in these 2 patients had similar ECG and electrophysiologic findings. Both were reproducibly induced by rapid atrial pacing. The atrial activation sequence and entrainment study proved that these atrial flutters were not isthmus-dependent. A high-right atrial site was identified as the critical site of the slow conduction zone of the tachycardia in both. This site showed double potentials and mid-diastolic potentials. Radiofrequency catheter ablation at this site successfully eliminated the isthmus-independent atrial flutter in both patients.