ATRIAL-FLUTTER MAPPING AND ABLATION .2. RADIOFREQUENCY ABLATION OF ATRIAL-FLUTTER CIRCUITS

The definition of the anatomical substrate of reentry in atrial flutte r has allowed the recognition of narrow, critical areas of the circuit , where radiofrequency ablation can interrupt reentry. In common fIutt er the isthmus between the inferior vena cava and the tricuspid valve appears the best target, but ablation between the coronary sinus and t ricuspid valve can also be effective in some cases. In atypical flutte r using the same circuit as common flutter in a ''clockwise'' directio n, ablation of the same isthmus is effective. Flutter interruption is the main objective, but it does not mean complete isthmus ablation. If flutter remains inducible, new applications are delivered in the isth mus, until it is made noninducible. Complications are rare. Despite at taining noninducibility, flutter may recur, and new procedures may be needed to prevent recurrence. Atrial fibrillation can occur in up to 3 0% of the cases during foIlow-up, but it is generally well controlled with antiarrhythmic drugs, that were ineffective to treat flutter befo re ablation. In reentry circuits based on surgical atrial scars, ablat ion of an isthmus between the scar and the inferior vena cava can also be effective. Left atrial circuits are not known well enough to guide successful ablation.