Monocenter Investigation Micra® MRI Study (MIMICRY): Feasibility Study of the Magnetic Resonance Imaging Compatibility of a Leadless Pacemaker System

Aims: As in vivo real-life data are still scarce, we conducted a study to assess the safety and feasibility of cardiac magnetic resonance imaging (MRI) in patients with a leadless pacemaker system.

Methods And Results: In this prospective non-randomized interventional trial, we enrolled 15 patients with an MRI conditional Micra® leadless pacemaker system to undergo either a 1.5 T or 3.0 T cardiac MRI scan. Clinical adverse events as well as device parameters such as pacing threshold, sensing, impedance, and battery life were assessed at baseline as well as 1 and 3 months after the scan. Device parameter changes between different time points were tested for statistical significance and compared with pre-set cut-off values. Fourteen patients underwent the cardiac MRI scan according to the protocol as well as the scheduled follow-up visits. One participant was excluded from analysis, as the MRI scan was not possible because of severe claustrophobia. Other clinical events did not occur during the scan and the follow-up period. Device parameters stayed stable and changes during the observational period were statistically not significant (changes vs. baseline: pacing threshold: 0.01 ± 0.05 V, P = 0.308, 0.01 ± 0.07 V, P = 0.419, sensing: -0.15 ± 1.11 mV, P = 0.658, -0.19 ± 1.17 mV, P = 0.800, impedance: -7.86 ± 30.7 Ohm, P = 0.447, -7.86 ± 25.77 Ohm, P = 0.183, at 1 and 3 months follow-up, respectively). Parameter changes were not statistically different between patients who underwent imaging at 1.5 T (n = 7) or 3.0 T (n = 7).

Conclusion: In our set of patients with a Micra® leadless pacemaker, cardiac magnetic resonance imaging at either 1.5 T or 3.0 T proved feasible and safe with no relevant changes in device parameters within 3 months of follow-up.