LEADLESS II: Leadless Pacemakers Safe, Effective for Single-Chamber Ventricular Pacing

A leadless pacemaker was safe and effective at six month follow-up.

Findings from the LEADLESS II trial support leadless pacemakers as an alternative to standard pacemakers for patients who need single-chamber ventricular pacing, according to researchers at the European Society of Cardiology 2015 Congress.

LEADLESS II was an observational FDA investigational device exemption study that followed 526 patients (median age 75.8 years) from 56 centers in Australia, Canada, and the United States. There was a primary cohort of 300 patients that researchers followed for 6 months. Each patient received an active fixation, rate-adaptive pacemaker designed to provide permanent, single-chamber ventricular pacing. Vivek Reddy, MD, from Icahn School of Medicine at Mount Sinai in New York City, and colleagues evaluated the clinical safety and efficiency of implanting leadless cardiac pacemakers using a steerable catheter.

“Leadless cardiac pacemakers have the potential to overcome many of the complications of conventional transvenous pacemakers,” said Dr. Reddy. “Transvenous leads are considered the Achilles heel of conventional pacemakers because they are particularly susceptible to complications.” These complications include infection, lead revision, and pocket revision.

The primary safety endpoint for the study was freedom from serious adverse device effects (SADEs) at 6 months; the primary efficacy endpoints were an acceptable pacing capture threshold (≤2.0 V at 0.4 milliseconds) and an acceptable sensing amplitude (R wave ≥5.0 mV or ≥implantation value).

The pacemaker was successfully implanted in approximately 96% of patients in the primary cohort. In the total cohort, 93% of patients achieved the safety endpoint and 90% achieved the efficacy endpoint, which exceeded the performance goals of 86% for safety and 85% for efficacy.

In the primary cohort, there was a 6.7% overall adverse event rate and a 1.3% cardiac perforation and vascular complication rate. Among the total cohort, the adverse event rate was 6.5%, the rate of cardiac perforation was 1.5%, and vascular complication was 1.1%.

Only 2 patients from the total cohort had a device migrate during implantation due to inadequate fixation — the device dislodgement rate in the primary cohort was 1.7% vs 1.1% in the total cohort. The device was successfully removed in all 7 patients who needed a replacement.

“When interpreted in the context of limited prior experience of the majority of operators with this new technology, these results provide support for the applicability of this technology in routine clinical practice,” said Dr. Reddy.

He noted that he expects the SADE rate to improve with increased operator experience, as 99 of 100 operators had never implanted a leadless pacemaker device before the trial. Although currently available leadless pacemakers manage only a single chamber, device-to-device communication is in development that could make dual chamber pacemakers and cardiac resynchronization therapy possible.

The projected longevity of the battery in leadless pacemakers is approximately 15 years, but Dr. Reddy concluded that further study is necessary to determine how to manage the pacemaker after the battery is depleted.

Disclosures: The LEADLESS II Trial was sponsored by St. Jude Medical, Inc., which manufactures the pacemakers. Dr. Reddy received consulting fees from St. Jude Medical, and serves as Chair of the Steering Committee for the trial.


  1. Reddy VY, Exner DV, Cantillon DJ, Doshi R et al. N Engl J Med. 2015; 373:1125-1135.