INTRODUCTION
Permanent pacemaker implantation is the only established treatment for bradyarrhythmia that contributes to improved life prognosis as well as quality of life. In the last 10 years, 50,000 implantable pacemakers have been introduced in Japan every year, and more than 60,000 cases have been recorded annually in recent years. In the United States, more than 350,000 pacemakers are implanted annually, and this number has doubled in the last 30 years.1 Elderly people are more prone to bradyarrhythmias, and it is estimated that more patients will need more pacemaker implants as the aging society advances. On the other hand, it has been reported that lead trouble and subcutaneous pocket complications, which are complications of conventional transvenous pacemakers, are present in 7% and 11% of cases at 5 years after implantation, respectively.2 The introduction of transcatheter pacing systems (TPSs) was expected to reduce lead and pocket complications. In previous studies, the TPS was shown to be an effective and safer option, reducing the common complications from conventional pacemakers and providing a more stable pacing threshold.3-6 However, some cases require a higher pacing threshold, because the latter increases post-implantation, which subsequently decreases battery longevity and increases the risk of an adverse heart event due to pacing issues. Predictors that require long-term high pacing thresholds have been reported,6but the cause of increased thresholds after implantation has not been clarified. Most of the rapid increases in pacing threshold occurred within one month of implantation, but there were few cases where the threshold was increased in the medium-to-long term.7-9Therefore, we hypothesized that it would be possible to obtain a stable pacing threshold in the long term if the increase could be avoided in the short term.
In this study, we investigated the clinical significance of early increased pacing threshold by comparing patient background characteristics, procedure-related indications, and threshold transition.