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Multicenter Study
. 2015 Oct 1;36(37):2510-9.
doi: 10.1093/eurheartj/ehv214. Epub 2015 Jun 4.

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

Philippe Ritter  1 , Gabor Z Duray  2 , Clemens Steinwender  3 , Kyoko Soejima  4 , Razali Omar  5 , Lluís Mont  6 , Lucas V A Boersma  7 , Reinoud E Knops  8 , Larry Chinitz  9 , Shu Zhang  10 , Calambur Narasimhan  11 , John Hummel  12 , Michael Lloyd  13 , Timothy Alexander Simmers  14 , Andrew Voigt  15 , Verla Laager  16 , Kurt Stromberg  16 , Matthew D Bonner  16 , Todd J Sheldon  16 , Dwight Reynolds  17 ; Micra Transcatheter Pacing Study Group
Collaborators, Affiliations
Multicenter Study

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

Philippe Ritter et al. Eur Heart J. .

Abstract

Aims: Permanent 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 results: Patients 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.

Conclusion: Early 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 registration: ClinicalTrials.gov ID NCT02004873.

Keywords: Leadless cardiac pacemaker; Miniaturization; Transcatheter pacing system.

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Figures

Figure 1
Figure 1
Transcatheter pacing system single-chamber ventricular pacemaker. Illustration of transcatheter pacing system positioned in the RV apex. RV, right ventricle.
Figure 2
Figure 2
Transcatheter pacing system delivery system. Tools needed to deliver transcatheter pacing system, from bottom to top: needle and guide-wire, introducer with dilator, delivery catheter with transcatheter pacing system retracted within the distal tube of the delivery system. Insert: transcatheter pacing system with Euro dollar to indicate scale.
Figure 3
Figure 3
Transcatheter pacing system deployment. Step 1, upper panel: the device is fully retracted within the delivery system. The distal end of the catheter is placed at the targeted site of the RV. Step 2, middle panel: the device is deployed and its tines penetrate the myocardium. Step 3, lower panel: the delivery catheter is pulled back from the device, which is still retained by a tether. After fixation and electrical checks, the tether will be cut and removed, as will the delivery system be. RV, right ventricle.
Figure 4
Figure 4
Flow diagram of patients analysed. Flow diagram from patients implanted by 11 August 2014 and analysed for early performance objectives.
Figure 5
Figure 5
X-rays of various device positions in RAO view. Left panel: apical device placement; Middle panel: mid-septal device placement; Right panel: right-ventricular outflow tract (RVOT) device placement.
Figure 6
Figure 6
Device electrical measures of first 60 patients. A, B, and C display the mean ± SD of the pacing threshold at 0.24 ms, R-wave amplitude, and impedance respectively for all data available from the 60 patients followed to 3 months. The P-value in A is for the comparison of the mean pacing capture threshold to the performance goal of 2.0V. **Significantly different from implant value.
Figure 7
Figure 7
Distribution of expected transcatheter pacing system battery longevity based on device use conditions (% pacing, heart rate, pacing capture thresholds) of first 60 patients through 3 months.
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