Different patterns of RR-NSVT
In the current study, half of the study patients experienced ≥ 1 episode of RR-NSVT and such incidence increased in a time-dependent matter, whereas those with ≥ 3 episodes almost reached a plateau. Currently, few studies evaluated the influence of different NSVT or RR-NSVT patterns that can predict further VTAs. Zecchin et al. reported that frequent NSVT (≥ 3 runs/day) was associated with an increased risk of mortality and VTAs in patients with severe LV dysfunction 6. Similarly, we identified a higher incidence of VTAs in patients with frequent RR-NSVT compared to those without a frequent pattern despite the presence of any RR-NSVT. However, most patients with frequent NSVT (12/21, 57.1%) experienced frequent RR-NSVT and subsequent VTA on the same day, which does not provide physicians with ample time to manage antiarrhythmic treatments. On the other hand, cluster NSVTs (≥3 episodes for 6 months) may serve as a better predictor of the following VTAs as the median time from cluster RR-NSVTs to VTAs was 105 days. Although we found borderline significance in the association between a cluster RR-NSVT and VTAs, this specific pattern of RR-NSVT is an important clue for further treatment during follow-up in such populations, especially in the current era in which home monitoring systems are available. Further studies to evaluate clinical influence of specific NSVT patterns are needed.