The unstable pacing thresholds of the leadless transcatheter pacemaker affected by body positions in subacute phase after implant

摘要

Background If the threshold at implant of leadless transcatheter pacemakers (LTPs) is less than 2.0?V, pacing thresholds reportedly decrease significantly by 1?month and maintain an optimal value of less than 1.0?V by 6?months. Case summary We report a case series of two patients with unstable pacing thresholds of the LTPs in the subacute phase after implant. The first patient (77-year-old man) was implanted an LTP for sick sinus syndrome. At that time of implant, the pacing threshold was 0.9?V at 0.24?ms. At 1?week and 1?month later, the threshold had increased to more than 2.0?V at 0.24?ms. We investigated the trend data for the week and found variations in the threshold. The second patient (81-year-old man) was implanted an LTP for bradycardia and atrial fibrillation. The pacing threshold at implantation was 0.63?V at 0.24?ms. One week later, the threshold had increased in supine position and decreased in sitting position. The trend data for the week were fluctuating greatly. Discussion The pacing threshold may increase to more than 2.0?V with significant fluctuation on assessment at 1?week and 1?month after implantation in association with changes in body position, even though we confirmed a stable threshold at implant. If an increased threshold is observed, it is necessary to check the trend data and threshold in each body position. Leadless pacemaker , Threshold ?Body position , Subacute phase , Fluctuation , Case series Learning points The pacing threshold may fluctuate significantly with change in body position in the subacute phase after leadless pacemaker implantation. Even if an optimal threshold and confirming stable fixation was obtained at implantation, the pacing threshold could be unstable on assessment at 1?week and 1?month. The only clues to an unstable threshold due to change in body position were the trend data after implantation. Therefore, it is important to check the trend data at a later time point. Furthermore, if a large fluctuation of the threshold is observed, we should check the pacing threshold according to changes in body position.