Three-dimensional nonfluoroscopic mapping and ablation of inappropriate sinus tachycardia. Procedural strategies and long-term outcome.

Objectives: We conducted this study to assess long-term results of three-dimensional (3-D) mapping-guided radiofrequency ablation (RFA) of inappropriate sinus tachycardia (IST). Change in activation after the administration of esmolol was also assessed and compared to the shift documented with successful sinus node (SN) modification.
Background: The long-term results after RFA of IST have been reported to vary between 27% and 66%.
Methods: Thirty-nine patients (35 women, mean age 31 +/- 9 years) with debilitating IST were included in the study. The area around the earliest site of activation recorded using the 3-D mapping system was targeted for ablation. The shift in the earliest activation site after administration of esmolol was compared with the shift after RFA.
Results: The heart rate at rest and in drug-free state ranged between 95 and 125 beats/min (mean 99 +/- 14 beats/min). Sinus node was successfully modified in all patients. Following ablation, the mean heart rate dropped to 72 +/- 8 beats/min, p < 0.01. The extent of the 3-D shift in caudal activation along the crista terminalis was more pronounced after RFA than during esmolol administration (23 +/- 11 mm vs. 7 +/- 5 mm, respectively, p < 0.05). No patient required pacemaker implantation after a mean follow-up time of 32 +/- 9 months; 21% of patients experienced recurrence of IST and were successfully re-ablated.
Conclusions: Three-dimensional electroanatomical mapping seems to facilitate and improve the ablation results of IST. The difference in caudal shift seen after esmolol administration and following SN modification suggests that adrenergic hypersensitivity is not the only mechanism responsible for the inappropriate behavior of the SN.