Limitations
There are several limitations to this study. First, the Micra-TPS was
implanted by two different cardiologists, which may have led to
technical differences in implantation. As the procedure was performed on
consecutive patients, the degree of proficiency of the cardiologists in
performing the procedure may have slightly varied. Second, there is a
limit in accurately determining the number of tines stably anchored to
the myocardium by the pull-and-hold method. Currently, some
facilities13 are making efforts to investigate tine
anchoring to the myocardium using intracardiac echo. If it is possible
to accurately evaluate the number of anchored tines, the number of tines
may potentially function as another predictor. Third, the follow-up
period for the SPT group was short, approximately 7 months on average,
and there is a possibility that a threshold increase may occur beyond
the follow-up period. Long-term continuous follow-up is, therefore,
necessary. We aim to clarify the involvement of threshold rise and
impedance by conducting a prospective study on the transition of the
pacing threshold according to implant impedance.