Discussion
Our main findings are as follows: (1) approximately 60% of the patients had no VT recurrences during a mean follow-up period of 2.5 years when PES was not implemented after VT ablation due to variable causes. (2) The prevalence of VT recurrence-free rate at 2 years after VT ablation was significantly higher in patients with non-inducibility before RF delivery than in those with other causes.
Non-inducibility after VT ablation is known as one of the ideal endpoints10. However, PES after VT ablation can be occasionally harmful or omitted under several circumstances20. Several retrospective studies evaluated the effect of non-inducibility after VT ablation and showed that 8%–16%12,21 of the patients who underwent VT ablation did not undergo PES after VT ablation. However, to our knowledge, no studies have described the rationales of these situations that are not infrequent to encounter in real-world clinical situation. Although the variety and frequency of the causes depend on the institutional or operator’s discretion, our study demonstrated that non-inducibility before ablation was the leading cause (reportedly, VTs are not inducible before ablation among 37% of VT ablation patients22). This was followed by long procedure time, complications, intolerant hemodynamic state, and inaccessible or unsafe targets.
With respect to the long-term follow-up, most of the studies evaluated VT recurrences of patients who did not undergo PES after VT ablation combined with patients who were still inducible after VT ablation12,14,23. No studies have investigated the VT recurrence in an independent untested group. Our study first demonstrated the long-term follow-up of this untested group that was approximately 60% VT-free during a mean follow-up of 2.5 years. Furthermore, the prevalence of VT recurrence at 2 years after VT ablation was significantly lower in patients with non-inducibility before RF delivery than those with other causes. This finding seems logically acceptable because the former was considered less arrhythmogenic while the latter was considered an incomplete procedure as shown by the prevalence of suspension before sufficient RF delivery in Table 3 . In addition, the long-term follow-up of untested group with non-inducibility before RF delivery shows as favorable result as the procedures with non-inducibility of target VTs (Supplementary Figure 1 ). Therefore, considering this finding with approximately 90% of VT-free survival rate at 2 years, PES after VT ablation might be not an ideal endpoint in patients with non-inducibility before RF delivery. Furthermore, importantly this etiology (so called untested PES at the end of ablation) was heterogeneous, which may require careful post-procedural follow-up based on the rationale of untested PES.