VT burden reduction
The term ”recurrence” has been used to evaluate the outcome of the ablation therapy, however, recently the concept of a VT burden reduction has been proposed.19, 20 The VT burden can be more valuable in terms of clinical benefit than recurrence as a dichotomous event. In the present study, the VT burden was reduced by 91.1% even in patients in whom VT non-inducibility could not be achieved at the end of RF ablation, and VT ablation significantly reduced the number of VT episodes and shock therapies. Although the design of the current study did not allow us to examine the prevention of mortality, a reduction in the ICD shock therapies may improve the patient survival.21
Clinical Implications
It is known that the achievement of VT non-inducibility at the end of the VT ablation in patients with SHD leads to a lower recurrence. So VT non-inducibility has been used as an endpoint in many cases. However, in some cases, the ablation may be excessive or the risk of an induction test may be high. In this study, we included patients in whom VT non-inducibility could not achieved at the end of the VT ablation. We found that the recurrence rate was lower in patients with an EF≥35% or in patients who could successfully identify and undergo ablation of all clinical VT isthmuses. In these patients, even if non-clinical VT inducibility remains, it may not affect the subsequent prognosis. In addition, the VT burden was reduced after the VT ablation, and the shock therapy was also significantly reduced before and after the ablation. That suggested that it may be necessary to examine the validity of the VT non-inducibility in each patient.
Study Limitations
This study was a single-center retrospective observational analysis. Therefore, the number of study patients was relatively small. And this study included the patients with ICM and NICM, and the NICM consisted of a non-uniform etiology. The response to the RF ablation and clinical course may differ for each cardiomyopathy. Further, the methods used for antiarrhythmic drugs were dependent on each physician. However, because of the limited number of operators, our strategy to treat patients with VTs has been consistent and our results can be applied to clinical practice.
Conclusion
Even if VT non-inducibility could not be achieved at the end of the RF ablation, 66% of the patients had no VT recurrences. Among them, in the patients whose LVEF was more than or equal to 35% or in whom all clinical VT isthmuses could be identified and ablated, that successful identification and ablation of those might prevent VT recurrences. In addition, even if the VT recurred, the VT burden decreased after the VT ablation. The validity of VT non-inducibility for any VT should be evaluated by each patient’s background and the results of the procedure.
Acknowledgments
The authors would like to thank Mr. John Martin for his linguistic assistance.
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