A self-contained, miniaturized, leadless transcatheter pacing system demonstrated excellent electrical performance and a rate of serious adverse events (AEs) in line with traditional transvenous pacing systems. Data from the Micra Transcatheter Pacing study [NCT02004873]—a first-in-human safety and efficacy study—were reported by Philippe Ritter, MD, Hôpital Haut-Lévêque, Pessac, France.

At 0.8 cc, the Micra pacing system is < 10% the size and mass of conventional transvenous pacing systems. The device is fixated directly in the right ventricle via the femoral vein through 4 protractible nitinol tines, and it delivers electrical impulses through an electrode.

Dr Ritter described the experience from the first 140 patients (mean age, 78 years) to undergo implantation during a single-arm 23-center global trial. All patients had class I or II indications for ventricular inhibited pacing, with the primary indication being bradycardia with permanent or persistent atrial tachyarrhythmia (65%). They were followed for an average of 1.9 months, with early performance analysis conducted in the first 60 patients who were followed to 3 months. Ninety-seven percent of patients had ≥ 1 comorbidity.

Outcomes of interest were serious AEs related to the device (as adjudicated by an independent clinical events committee) and the electrical parameters and function of the device.

Implant success was 100%. Mean implant time was 37 minutes, and the median number of deployments per procedure was 1. Site implant was the apex in 77%, septum in 16%, midseptum in 6%, and right ventricular outflow tract in 1%. At baseline, 44% of patients were on anticoagulation, and 29% were on antiplatelet agents. During the procedure, 40% of patients received a heparin intravenous bolus. One patient died from a noncardiovascular-related cause 139 days after implant. There were no procedure-related deaths.

The rate of serious AEs was 5.7%, a rate comparable to the 7.3% rate observed in a Medtronic reference data set, said Dr Ritter. There were no unforeseen events, device telemetry issues, dislodgements, infections, reoperations, or related deaths. Eight patients had a total of 9 serious AEs related to the device or procedure, resulting in 2 prolonged hospitalizations (> 48 hours; Table 1). One patient had a pericardial effusion without tamponade after persistent device repositioning, which was resolved with drainage. Another patient was hospitalized after an arterial pseudoaneurysm.

Electrical measurements, including R-wave sensing amplitude and pacing, were as expected. Specifically, the median pacing percentage was 49%; the median pacing capture threshold at 0.24 milliseconds was 0.38 V; and the median pacing impedance was 640 Ω. Based on the mean pacing percentage, the projected battery longevity is estimated at an average of 12.6 years.

A miniaturized leadless pacing system is a promising solution to permanent cardiac pacing that may reduce the risks associated with traditional technology and improve patient satisfaction, said Dr Ritter. Long-term safety and benefit are being evaluated in an ongoing clinical trial.