Percutaneous Implantation of a Leadless Pacemaker
What is the clinical safety and efficacy of nonsurgical implantation of a leadless cardiac pacemaker in patients who require permanent ventricular pacing?
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).
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%).
The authors concluded that the leadless cardiac pacemaker met prespecified pacing and sensing requirements in the large majority of patients in their study.
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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