Sub-Acute Re-Elevated Pacing Thresholds After Atrial Leadless Pacemaker Implantation.

INTRODUCTION: The safety and efficacy of the atrial leadless pacemaker (A-LP) with helix fixation have been demonstrated. Usually, elevated acute thresholds decrease gradually and normalize within 24 h. Here, we report a case of subacute re-elevation of pacing thresholds after hospital discharge. CASE PRESENTATION: An 80-year-old female with a history of bradycardia underwent A-LP implantation. At the time of the procedure, the final pacing threshold (PT) was measured at 4.0 V/0.4 ms. On post-procedural Day 1, the PT at 0.4 ms pulse width decreased to 1.0 V. On Day 4, the PT was 1.0 V/0.4 ms prior to the patient's discharge. However, on Day 5, she was readmitted to the hospital due to the loss of atrial capture at the maximum output available after an intravenous administration of 150 mg amiodarone for atrial flutter. Over 3 days of monitoring, atrial PT was higher than 6 V/1.5 ms. A traditional DDD pacemaker was implanted due to recurrent sinus asystole associated with dizziness. At the 1-month follow-up, the PT of atrial A-LP was 0.5 V/0.4 ms. Two months later, an ambulatory Holter confirmed the stable and normal atrial capture of the A-LP after lowering the base rate of the DDD pacemaker. At the 3-month follow-up, PT of the A-LP remained 0.5 V/0.4 ms. CONCLUSION: Sub-acute re-elevated PT of the A-LP during the perioperative period may persist for more than 1 week and then normalize within 1 month. If PT re-elevation is suspected to be related to peri-electrode inflammation, a conservative approach with continued monitoring of threshold changes may be considered.