A leadless cardiac pacemaker (LCP) system was demonstrated to be safe and effective in patients who required single-chamber ventricular pacing. Vivek Y. Reddy, MD, Mount Sinai Hospital, New York, New York, USA, presented data from the study of percutaneous implantation of an entirely intracardiac leadless pacemaker [LEADLESS II; Reddy VY et al. N Engl J Med. 2015].

Current implantable cardiac defibrillators (ICDs) are associated with potential problems such as lead failure, device pocket infection, hematomas, discomfort, and complication rates up to 15% [Udo EO et al. Heart Rhythm. 2012]. The leadless pacemaker was developed as a strategy to avoid surgery and use of leads. The purpose of the LEADLESS II trial was to determine the safety and efficacy of the LCP system.

In the prospective, multicenter, nonrandomized LEADLESS II trial, patients indicated for VVI(R) pacemaker implantation received the LCP. The LCP is delivered percutaneously through the femoral vein and is self-contained within the ventricle. The primary efficacy end point was acceptable pacing capture threshold and therapeutically acceptable sensing amplitude up to 6 months. The primary safety end point was freedom from device-related serious adverse events (SAEs) at 6 months. The primary cohort analysis was of the first 300 patients; safety and efficacy were analyzed in the intention-to-treat (ITT) population.

Patients were eligible for enrollment if they had chronic atrial fibrillation or normal sinus rhythm with secondary or tertiary atrioventricular or bifascicular bundle branch block, or sinus bradycardia with infrequent pauses or unexplained syncope. At baseline, the mean age in the primary cohort was 75.7, the mean body mass index was 29.2, 64.3% of patients were men, and 89.7% were white. In addition, coronary artery disease was present in 40.3%, hypertension in 84%, diabetes mellitus in 27.3%, and tricuspid valve disease with regurgitation or prolapse in 19.7%, and the mean left ventricular ejection fraction was 57.1%.

In the LEADLESS II trial, the total duration of the procedure in the primary cohort was 50 minutes, with the insertion to removal of the delivery catheter lasting 30.4 minutes. Device repositioning was required once in 18.3% of patients and twice in 8.3% of patients. The final location of the LCP was within the apex in 48.4% of patients; in the outflow, septum, or other area in 49.8%; and in the apical septum in 1.7%.

The primary safety end point was achieved in 93.3% of patients (95% CI, 89.9 to 95.9; P < .001), and the efficacy end point was achieved in 90% (95% CI, 86 to 93.2; P = .007). LCP implantation was successful in 93.4% of patients (95% CI, 89.9 to 96; P = .001). Freedom from SAEs at 6 months was 97.5% in the primary cohort, with the most common device-related SAEs including cardiac perforation and vascular complications (Table 1). Dr Reddy pointed out that most SAEs occurred within the first several weeks after implantation.

Dr Reddy concluded that the safety and efficacy data from the LEADLESS II trial suggest that the LCP system is a feasible alternative to the standard implantable pacemakers in patients who require single-chamber ventricular pacing.