Cavotricuspid isthmus mapping to assess bidirectional block during common atrial flutter radiofrequency ablation

Background-We sought to compare published methods to an alternative approac h ascertaining cavotricuspid isthmus (CTI) block during atrial flutter abla tion. Methods and Results-In 39 consecutive patients who underwent an atrial flut ter ablation procedure, a 24-pole mapping catheter was positioned so that 2 adjacent dipoles were bracketing the targeted CTI line of block (LOB), wit h proximal dipoles lateral to the LOB and distal dipoles in the coronary si nus. Two pacing sites were lateral (positions A and B) and 2 were septal (p ositions C and D) to the LOB, with locations A and D closest to the LOB. A resulting CTI block was accepted when 3 criteria were fulfilled: (1) comple te reversal of the right atrial depolarization on the 24-pole catheter when pacing in the coronary sinus, (2) conduction delays from A to D greater th an from B to D, and (3) conduction delays from D to A greater than from C t o A. A successful CTI block was obtained in all patients. Before CTI block was obtained? a progressive CTI conduction delay was observed in ii patient s (28.2%). During the procedure, the 3 criteria defined above were either a ll present or all absent. Conclusions-This study establishes that reversal of the atrial depolarizati on sequence up to the LOB is a definitive and mandatory criteria of success ful atrial flutter ablation.