ABLATION OF INCISIONAL REENTRANT ATRIAL TACHYCARDIA COMPLICATING SURGERY FOR CONGENITAL HEART-DISEASE - USE OF ENTRAINMENT TO DEFINE A CRITICAL ISTHMUS OF CONDUCTION

Background Intra-atrial reentrant tachycardia occurs frequently after surgery for congenital heart disease and is difficult to treat. We tes ted the hypotheses that intra-atrial reentrant tachycardia in patients who had undergone prior reparative surgery for congenital heart disea se could be successfully ablated by targeting a protected isthmus of c onduction bounded by natural and surgically created barriers and that entrainment techniques could be used to identify these zones. Methods and Results Eighteen consecutive patients with 26 intra-atrial reentra nt tachycardias complicating surgery for congenital heart disease (9 a trial septal defect repair, 4 Fontan, 2 Mustard, 2 Senning, and 1 Rast elli procedure) underwent electrophysiological study and ablation atte mpts. Mapping of activation was facilitated by the deployment of cathe ters with multiple electrodes. Sites for ablation were sought that dem onstrated entrainment with concealed fusion and at which the postpacin g interval minus the tachycardia cycle length and the stimulus to P wa ve minus the activation time were <30 ms. These sites were considered to be within a narrow isthmus critical to the tachycardia mechanism. A natomic barriers bordering the critical isthmus of conduction were ide ntified on anatomic grounds, by the presence of areas of electrical si lence or by the demonstration of split potentials signifying a line of block. Success was achieved in 15 patients with 21 arrhythmias. The m edian number of radiofrequency applications was 5. There was a wide ra nge of activation times at successful sites (-30 to -250 ms). At a mea n duration of follow-up of 17+/-8 months, 11 patients were asymptomati c and 9 did not require antiarrhythmia therapy. Conclusions Successful ablation of intra-atrial reentrant tachycardia complicating surgery f or congenital heart disease may be achieved by creation of an ablative lesion in a critical isthmus of conduction bounded by anatomic barrie rs. This isthmus may be identified by the presence elf entrainment wit h concealed fusion and an analysis of the relationship between the pos tpacing interval and the tachycardia cycle length and between the acti vation time and the stimulus time. Because this isthmus is invariably confined on at least one aspect by a surgical repair site that is of c entral importance to the tachycardia mechanism, we suggest that this t ype of arrhythmia be given the descriptive designation of ''incisional reentry.''