Incidence and Clinical significance of ATP-induced AF
Previous studies reported that the incidence of ATP/Adenosine-induced AF was 29.6 and 47% before PV isolation;7, 8 and 5.6 to 13% after PV isolation.9, 10, 11 Most of these foci located in PV and SVC. When excluding non-PV/non-Box and non-SVC foci, the incidence of ATP-induced AF was 2.5% and 15% before PV isolation; and 2.4% to 7.4% after PV isolation in these studies. These were still higher than the incidence of the present study.
The difference in the incidence of ATP-induced AF from non-PV foci was mainly due to various induction protocols. Tutuianu et al. used adenosine of 18 or 36 mg for induction,8 equivalent to about 34 or 68 mg of ATP according to each molecular weight. The excessive dose may lead to provoke non-clinical and non-specific triggers. The dose of ATP and isoproterenol in the present study was lower than previous studies because the purpose of ATP injection was to unmask dormant conduction between LA and the isolated areas, not to induce AF.
Tutuianu et al. also reported that adenosine much more frequently induced non-PV triggered AF as compared with ISP (3 to 20 mcg/min); then, they concluded that there was no correlation between non-PV triggers with ATP and arrhythmia recurrence.8
In contrast, Kuroi et al. administered 30 mg of ATP after PVI and identified that ATP-provoked AF originating from the atria (not from SVC) was the independent predictor of a recurrence of arrhythmia even after the repeat procedure.10
Tao et al. administered 20 mg of ATP before PVI, and they revealed that ATP-induced AF was documented from the same site as the spontaneous AF in 41% of patients.7
Similar to the incidence of AF induction, the difference in the induction protocols might lead to a discrepancy in the clinical significance. The different patient populations and a limited number of cases who undergo the repeat procedure to confirm the relationship between the AF recurrence and the ATP-provoked foci also might be related to the discrepancies.
In our study patients, only 20 mg of ATP injection following PV/Box isolation (and SVC isolation in 4 of 7 patients) reproducibly induced AF. Therefore, mapping and ablation of non-PV/non-Box foci were thought to be mandatory, and the ablation resulted in favorable clinical outcomes.