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.