Early performance of a miniaturized leadless cardiac pacemaker: the Micra Transcatheter Pacing Study

Abstract

AimsPermanent cardiac pacing is the only effective treatment for symptomatic bradycardia, but complications associated with conventional transvenous pacing systems are commonly related to the pacing lead and pocket. We describe the early performance of a novel self-contained miniaturized pacemaker.Methods and resultsPatients having Class I or II indication for VVI pacing underwent implantation of a Micra transcatheter pacing system, from the femoral vein and fixated in the right ventricle using four protractible nitinol tines. Prespecified objectives were >85% freedom from unanticipated serious adverse device events (safety) and <2 V 3-month mean pacing capture threshold at 0.24 ms pulse width (efficacy). Patients were implanted (n = 140) from 23 centres in 11 countries (61% male, age 77.0 ± 10.2 years) for atrioventricular block (66%) or sinus node dysfunction (29%) indications. During mean follow-up of 1.9 ± 1.8 months, the safety endpoint was met with no unanticipated serious adverse device events. Thirty adverse events related to the system or procedure occurred, mostly due to transient dysrhythmias or femoral access complications. One pericardial effusion without tamponade occurred after 18 device deployments. In 60 patients followed to 3 months, mean pacing threshold was 0.51 ± 0.22 V, and no threshold was ≥2 V, meeting the efficacy endpoint (P < 0.001). Average R-wave was 16.1 ± 5.2 mV and impedance was 650.7 ± 130 ohms.ConclusionEarly assessment shows the transcatheter pacemaker can safely and effectively be applied. Long-term safety and benefit of the pacemaker will further be evaluated in the trial.Clinical Trial RegistrationClinicalTrials.gov ID NCT02004873.

Leadless Pacemakers: practice and promise in congenital heart disease

“…Although passing a large bore catheter through the tricuspid valve may be technically challenging after surgical repair, the ability to pace the right ventricle without having to leave a lead traversing the valve would be advantageous. Trial data shows that implant times are short (mean time of implant 28.6 ± 18.7 min for Nanostim [16] and 37 ± 21 min for Micra [20]) which compares well with standard leaded VVI implants.…”

“…The recent report of Micra performance showed 100% implant success, but an 18.6% rate of procedure-related adverse events. Perforation was less of a problem than with Nanostim (0.7 vs 1.5%) but the rate of vascular complications was higher, including bleeding in 2.1% of patients, haematoma in 1.4%, and pseudoaneurysm in 1.4% [20]. This reflects the larger caliber of the implant sheath (27 F) for the shorter, wider Micra than the 16 F sheath used for the longer, thinner Nanostim.…”

“…The limited duration of follow-up with leadless devices makes it difficult to accurately predict battery longevity but battery depletion for leadless devices should be slower than for conventional devices due to the absence of leads and developments in low-power electronics and battery technology which are likely to offset the smaller size of leadless device batteries. The estimated average longevity of the Nanostim is 15.0 years [16] and the Micra 12.6 years [20] which exceeds the lifespan of conventional devices. The most difficult question that remains to be definitively answered regarding leadless devices is what to do when the battery is depleted.…”

“…lead) and limited content of ferromagnetic components makes leadless pacemakers much more readily MR-conditional [23]. Both Nanostim and Micra are safe for full body magnetic resonance imaging in 1.5 and 3.0 T scanners and it is likely that they will be suitable for scanning in more powerful magnets in the future [16,20]. They will certainly be more able to keep pace with developments in MR technology than traditional leaded devices.…”

Report of the American Heart Association (AHA) Scientific Sessions 2015, Orlando

“…Major complications occurred in 4% of the patients, which was 51% less than in the transvenous pacemaker control group. 12 Periprocedural Safety of Left Atrial Appendage Occlusion With the Watchman Device: Preliminary Data From the EWOLUTION Registry Current ESC guidelines recommend left atrial appendage (LAA) closure in patients with a contraindication to oral anticoagulation and an increased risk of stroke. Preliminary data from the EWOLUTION registry of LAA occlusions with the Watchman device (Boston Scientific Corporation) were presented.…”