INTRAATRIAL REENTRANT TACHYCARDIA AFTER PALLIATION OF CONGENITAL HEART-DISEASE - CHARACTERIZATION OF MULTIPLE MACROREENTRANT CIRCUITS USINGFLUOROSCOPICALLY BASED 3-DIMENSIONAL ENDOCARDIAL MAPPING

Catheter Mapping of IART. Introduction: The anatomic substrate of intr a-atrial reentrant tachycardia (IART) following congenital heart surge ry is poorly understood, but is presumed to be different than common a trial flutter. Methods and Results: To study the mechanisms of IART, w e used a new technique for high-density endocardial mapping using reco rdings from a multipolar basket recording catheter (25 bipolar pairs), For each recording, biplane fluorographic reference points were digit ized to obtain the spatial locations of electrode pairs, and activatio n times were calculated using temporal reference points from the surfa ce EGG. Using custom software, data were combined to create three-dime nsional atrial activation sequence maps, which were displayed as anima ted sequences. Using this technique, recordings were made in induced a nd/or spontaneous IART in 8 patients following congenital heart surger y (5 Fontan, 2 tetralogy of Fallot repair, 1 ventricular septal defect repair), and in 3 patients with normal intracardiac anatomy (1 with t ype I atrial flutter). Ten discrete IART activation sequences were rec orded; 2 patients had 2 sequences each. IART maps were constructed usi ng a median of 108 electrode positions (range 27 to 197) from a median of 6 recordings/sequence (range 3 to 11). Sinus or paced atrial rhyth ms were also recorded, and maps were created in a similar fashion, Vis ual analysis of activation sequences of sinus and paced rhythm were an atomically concordant with known mechanisms of atrial activation. IART sequences revealed diverse mechanisms; only 1 IART circuit was simila r to that associated with common atrial flutter. Activation wavefront emergence from presumed zones of slow conduction, lines of conduction block, and apparent bystander activation were observed. Conclusions: H igh-density atrial activation sequence maps demonstrate that IART foll owing congenital heart surgery utilizes diverse circuits and is distin ct from common atrial flutter. The technique used to create these thre e-dimensional activation sequences may improve understanding of these complex atrial arrhythmias and assist in the development of ablative t herapies.