P438
Safety and efficacy of the Micra Transcatheter Pacemaker in different right ventricular positions

Background: The Micra Transcatheter Pacemaker (TCP) proved to be safe and effective. The delivery tool has been designed for implantation of the totally intracardiac single-chamber device in the right ventricular apical (A) position, however implanting physicians tend to implant the device in different septal (low – LS, mid – MS) positions and in some cases in the right ventricular outflow tract (RVOT). Currently, there is limited data available on safety and efficacy of the Micra TCP in different RV positions.

Methods: Freedom from device-, or procedure-related adverse events at 6 months as well as electrical data up to 18 months were collected and analyzed in 55 Micra pacemaker recipients in a single centre. Threshold (T, at 0.24 msec), impedance (I) and R-wave amplitude (R) were compared in different right ventricular pacemaker positions at implant, 1, 3, 6, 12 and 18 months.

Results: All 55 patients (76±8 years, 17 female) received a Micra TCP with 0.59±0.44 V T, 741±217 Ohms I, and 14.4±4.4 mV R at implant. The T and I remained stable during all measurements such as 0.57±0.24 mV, 576±84 Ohms; 0.57±0.38 mV, 574±95 Ohms; 0.57±0.27 mV, 635±92 Ohms; and 0.60±0.26 mV, 583±184 Ohms in MS, LS, A and RVOT positions at 12 months, without significant differences between positions at any follow-ups. The R was similar at implant 11.8±4.7, 13.5±4.6, 13.0±4.0, 10,9±3.7, however, a lower R wave was observed in RVOT from pre-discharge measurement onwards with minimum at 1 months (12.0±5.1, 14.6±5.1, 17.0±4.2, 5.1±3.1). This lower R wave amplitude did not lead to clinically detected undersensing or to a need for device revision either. There were two major adverse events, one in the A, one in the LS group without differences between the positions.

Conclusion: Micra TCP can be positioned and deployed in different right ventricular positions safely. Appropriate electrical performance is achievable in all positions; however, R wave amplitude tends to be smaller in the RVOT position without clinical significance.