ANATOMICALLY BASED ABLATION OF ATRIAL-FLUTTER IN AN ACUTE CANINE MODEL OF THE MODIFIED FONTAN OPERATION

Background: Lateral tunnel total cavopulmonary connection, also called the modified Fontan operation, uses a baifle through the right atrium . We established, in an acute canine model, that atrial Butter alter t otal cavopulmonary connection revolves around a line of conduction blo ck imposed by the free wall lateral tunnel suture fine, We hypothesize d that a line of conduction lock between the free wall total cavopulmo nary connection suture hue and the tricuspid anulus would interrupt at rial flutter in this model, Objective: Our objective was to determine whether a cryolesion placed between the free wall total cavopulmonary connection suture hue and the tricuspid anulus would terminate atrial Butter in an acute canine model, Methods: Seven adult dog underwent me dian sternotomy and institution of cardiopulmonary bypass, A suture li ne was placed through a right atriotomy to simulate total cavopulmonar y connection lateral tunnel construction, Form-fitting 253-point biatr ial endocardial mapping electrodes were placed via bilateral ventricul otomies, Atrial flatter was induced by atrial burst pacing, A cryother mal lesion was then placed between the free wall total cavopulmonary c onnection suture fine and the tricuspid anulus in the low lateral righ t atrium (ia, CRYO 1 procedure), and reinduction of atrial flutter uas attempted, If atrial flutter was reinduced, the cryolesion was modifi ed superiorly to include the caudal portion of the atriotomy (i,e,, CR YO 2 procedure), Activation sequence maps were generated for sinus rhy thms before and after the cryolesions were placed and for induced arrh ythmias. Results: In an seven eases, atrial flutter was inducible afte r suture line placement, before placement of a cryolesion. The reentra nt circuit incorporated both caval orifices in five of seven eases and was successfully ablated by the CRYO 1 approach in each case Atrial. Butter was not inducible after placement bf the CRYO 2 lesion in the r emaining two cases, in which break-through Of the wave front occurred across the lateral tunnel suture line in the intercaval region. Activa tion sequence maps of sinus rhythm after placement of the cryolesions demonstrated a conduction block at the site of the lesion, Conclusions : A linear cryothermal lesion placed between the free wall aspect of t he total cavopulmonary connection suture line and the tricuspid anulus created a line of conduction block that successfully ablates atrial f lutter in the canine model.