Long-term outcomes in leadless Micra transcatheter pacemakers with elevated thresholds at implantation: Results from the Micra Transcatheter Pacing System Global Clinical Trial

Abstract

Pacing thresholds in most Micra patients with elevated thresholds decrease after implant. Micra device repositioning may not be necessary if the pacing threshold is ≤2 V.

Very high pacing thresholds during long‐term follow‐up predicted by a combination of implant pacing threshold and impedance in leadless transcatheter pacemakers

“…The percentage of patients with a high IPT (>1 V/0.24 ms) was similar to that observed in the largest Micra transcatheter registry 10 . Whereas Piccini et al 6 focused on the evolution of high or VHPT during the first year postimplant, this study addressed the possibility to predict VHPT during follow‐up and developed an algorithm that may help in the decision to reposition the device or not.…”

“…As previously described, 6,10,13 pacing thresholds tend to decrease during the first day's postimplant. This phenomenon could be explained by mechanical injury at the site of Micra electrode contact or if the nitinol tines generate small forces that draw the cathode to the tissue interface.…”

“…A previous study by Piccini et al 6 defined a pacing threshold greater than 1 V/0.24 ms as a high pacing threshold. On the other hand, the authors described poor success in decreasing the pacing threshold in patients who reached greater than 2 V/0.24 ms. As the longevity of the Micra‐TPS could be severely reduced at these thresholds, we defined greater than 2 V/0.24 ms as a VHPT.…”

Next-generation pacemakers: from small devices to biological pacemakers

“…In such devices, the pulse generator, the battery, and the sensing and pacing electrodes are self-contained in a small capsule designed to be delivered into the right ventricle through a steerable sheath inserted through the femoral vein 60,61 . The major limitations of current leadless pacemakers are the need for a large-bore (18–24 French) venous delivery system, the uncertainty about infectious and thrombogenic risks, and their capacity to provide only single-chamber RV pacing 44 .…”

“…To solve lead-related complications as well as infections associated with subcutaneous (extravascular) generators, leadless pacemakers have some promise 59–61 . Although leadless pacemakers have been used in patients with device-related infections 67 , the risk of bacteraemic ‘seeding’ of the leadless device remains to be studied in the long term.…”