Catheter ablation of atrial flutter circuits.

Atrial flutter (AF) mapping has shown circular activation in the right atrium (RA), with a "counterclockwise" rotation in a frontal view. The myocardial isthmus between the inferior vena cava and the tricuspid valve (IVC-T) closes the activation circuit in its caudal end. The reproducibility of this activation pattern, and the fact that some "rare" AF with a "clockwise" rotation of activation use the same circuit, suggests that reentry is greatly facilitated by the anatomical arrangement of the caudal end of the RA. This suggested that ablation of the IVC-T isthmus may interrupt AF and prevent its recurrence. We have applied radiofrequency (RF) current to the IVC-T isthmus in nine patients, producing sudden interruption of activation at this point in five (all those treated with large surface electrode catheters). In three others, RF produced acceleration or disorganization, leading to interruption. Preliminary follow-up data suggest a favorable effect on AF recurrence, either by preventing it, or by making antiarrhythmic drugs effective.