Typical atrial flutter ablation outcome: correlation with isthmus anatomy using intracardiac echo 3D reconstruction

AIMS: To verify if sites of conduction gaps on the isthmus correlate with anatomical peculiarities using the intracardiac echo (ICE) and a new 3D device to reconstruct the isthmus in patients undergoing cavotricuspid isthmus ablation. METHODS AND RESULTS: Twenty patients underwent isthmus ablation using an 8 mm tip ablation catheter. Two-dimensional and 3D ICE reconstruction of the isthmus was made before, during and after ablation. At the end of the lesion line isthmus block was validated by electrophysiological criteria. In case of its absence we closed the remaining conduction gaps verifying the position of the sites with ICE. Fourteen patients required a median of 8 RF pulses to obtain complete isthmus block (Group A). In the remaining 6 patients isthmus block was obtained with a median of 25 RF pulses due to conduction gaps 'resistant' to ablation (Group B). Conduction gap positions assessed by ICE were located in the central portion of the isthmus below the coronary sinus os in 71% of cases in Group A and along a prominent Eustachian ridge in Group B patients, respectively. 3D reconstruction showed a smooth isthmus in Group A with a 'peak and valleys' isthmus in Group B. In these latter patients isthmus block was obtained only after the complete ablation of the prominent Eustachian ridge. CONCLUSION: The isthmus presents anatomical variants particularly due to Eustachian ridge peculiarities which may represent a site of conduction gaps "resistant" to ablation.