Ablation strategy for ATP-induced AF
According to the current expert consensus statement on catheter and surgical AF ablation, if a reproducible initiation of AF from non-PV foci after PV isolation, focal ablation at the site of origin should be considered.14 However, localization and elimination of non-PV AF triggers can be challenging because of the transient nature of non-PV triggers and diverse locations to perform focal ablation.
Zhang et al. reported the foci triggering AF could not be localized because of the transient effect of ATP in 10 out of 39 patients.9 Kuroi et al. reported the patients with atrial AF foci had worse clinical outcomes than patients with SVC foci.10
Thus, these previous studies imply the difficulty of identifying the precise foci from the initial beat using the current mapping techniques. Some of these unidentified or residual foci might be associated with GP. In our study patients, we could eliminate non-PV foci by the GP-based approach without performing detailed activation mapping. In this context, targeting the GP site, not the presumably earliest site, might be a useful alternative ablation strategy in patients with ATP-induced AF.
However, we should recognize the high specificity but low sensitivity of the vagal response to HFS.
Calò et al. demonstrated the efficacy of GP ablation in RA in patients with vagal paroxysmal AF. Thirty-four patients were randomly assigned for a selective ablation at sites with positive HFS response or an extensive approach at anatomic sites of GP. They concluded that the anatomical ablation of RA GPs is effective in about 70% of patients.15 They did not perform PV and SVC isolation in both groups, whereas we employed the GP-based approach after PV/Box and SVC isolation. These lesion sets should affect some parts of the posterior and superior RA GP. Therefore extensive anatomic ablation of posterior and superior RA GP might not be necessary for our patients.
Recently, cardioneuroablation targeting the fractionated atrial potentials during sinus rhythm, called AF-Nest, has been applied to vagal AF.16, 17 Pachon et al. demonstrated a mean of 33.6±13 AF-Nest ablation completely abolished the vagal response induced by pulsed electric field delivered from the internal jugular vein.17
If our approach did not suppress the ATP-induced AF, we should consider performing these extensive ablation techniques. These extensive or anatomical ablations have potential risks of complications such as inappropriate sinus tachycardia and risks of recurrence as atrial tachycardia caused by formation of an arrhythmogenic substrate or critical channels among the cloud-like lesions.
Nevertheless, prospective randomized controlled study is warranted to determine the optimal ablation strategy for ATP-induced AF after PV/Box and SVC isolation.