Slow potential-guided radiofrequency catheter ablation in atrioventricularnodal reentrant tachycardia: Characteristics of the potential associated with successful ablation

To examine the characteristics of Haissaguerre's slow potential (SP) specif ic to effective catheter ablation of the slow path way in AV nodal reentran t tachycardia, the properties of SP and its recording site were analyzed in 52 patients who underwent successful SP-guided ablation. The properties of SP included the ratio of the amplitude of SP to that of atrial potential ( A)(SP/A), the SP duration, the interval between His-bundle potential (HP) a nd SP (HP-SP), the interval between A and SP IA-SP), the interval between S P and ventricular potential (V) (SP-V), and the ratio of A-SP to the interv al between A and the V (A-SP/A-V). The SP recording site was determined by the ratio of the amplitude of A to that of V (A/V) and by the relative posi tion of the ablation catheter on X ray (right anterior oblique projection), expressed as the ratio of the distance between the coronary sinus ostium a nd SP site to that between the coronary sinus ostium and HP recording site (relative SP position). Twenty-eight slow pathways were ablated with a sing le energy application, while the other 24 required applications greater tha n or equal to 2. In all successful applications, SP/A, SP duration, HP-SP, A-SP, SP-V A-SP/A-V A/V, and relative SP position were 51% +/- 25%, 28 +/- 5 ms, -11 +/- 9 ms, 57 +/- 25 ms, 68 +/- 13 ms, 46% +/- 9%, 15% +/- 13%, an d 52% +/- 13%, respectively. A significant correlation was observed between the relative SP position and A-SP, and between the relative SP position an d A-SP/A-V (r = 0.60 and 0.37, respectively), while it was not between the relative SP position and HP-SP, nor between the relative SP position and SP -V. When the characteristics of SP were comparatively analyzed between the effective and ineffective applications in 24 patients in whom applications greater than or equal to 2 were required, there was no difference observed in HP-SP, A-SP, SP-V, A-SP/A-V, and A/V. However, SP/A, SP duration, and th e relative SP position in the effective applications were all greater than those in the ineffective ones (56% +/- 20% vs 35% +/- 18%, P < 0.001; 29 +/ - 4 vs 26 +/- 5 ms, P < 0.01; and 52% +/- 15% vs 33% +/- 11%, P < 0.001, re spectively. These results indicate that SP with an amplitude over a half of A amplitude and recorded at the mid-septum of the tricuspid annulus can be a marker for successful slow pathway ablation. Although the local atrial e lectrogram appears late as the SP recording site shifts to the lower positi on, the timing of SP relative to HP and V remained unchanged, suggesting th at SP is independent of the local atrial activation.