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.