Percutaneous Implantation of a Leadless Pacemaker

Study Questions:

What is the clinical safety and efficacy of nonsurgical implantation of a leadless cardiac pacemaker in patients who require permanent ventricular pacing?

Methods:

In this multicenter study, the LEADLESS II investigators implanted an active-fixation leadless cardiac pacemaker (Nanostim, St. Jude Medical) in patients who required permanent single-chamber ventricular pacing. The primary efficacy endpoint was both an acceptable pacing threshold (≤2.0 V at 0.4 msec) and an acceptable sensing amplitude (R wave ≥5.0 mV, or a value equal to or greater than the value at implantation) through 6 months. The primary safety endpoint was freedom from device-related serious adverse events through 6 months. In this ongoing study, the prespecified analysis of the primary endpoints was performed on data from the first 300 patients who completed 6 months of follow-up (primary cohort). The rates of the efficacy and safety endpoints were compared with performance goals (based on historical data) of 85% and 86%, respectively. Additional outcomes were assessed in all 526 patients who were enrolled as of June 2015 (the total cohort).

Results:

The leadless pacemaker was successfully implanted in 504 of the 526 patients in the total cohort (95.8%). The intention-to-treat primary efficacy endpoint was met in 270 of the 300 patients in the primary cohort (90.0%; 95% confidence interval [CI], 86.0-93.2; p = 0.007), and the primary safety endpoint was met in 280 of the 300 patients (93.3%; 95% CI, 89.9-95.9; p < 0.001). At 6 months, device-related serious adverse events were observed in 6.7% of the patients; events included device dislodgement with percutaneous retrieval (in 1.7%), cardiac perforation (in 1.3%), and pacing-threshold elevation requiring percutaneous retrieval and device replacement (in 1.3%).

Conclusions:

The authors concluded that the leadless cardiac pacemaker met prespecified pacing and sensing requirements in the large majority of patients in their study.

Perspective:

This observational multicenter study reports that the Nanostim leadless cardiac pacemaker was capable of providing effective pacemaker function in a varied group of patients who had indications for long-term pacing therapy. Given the observational design of the study, mean follow-up of 6 months, and the ability to serve as only a single-chamber ventricular pacemaker, improvements in device-to-device communication, atrial affixation, device diagnostics, and longer-term follow-up are indicated for this device to challenge conventional dual-chamber pacemakers. The technology does look promising.


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