• Vivek Y Reddy, Derek V Exner, Daniel J Cantillon, Rahul Doshi, T Jared Bunch, Gery F Tomassoni, Paul A Friedman, N A Mark Estes, John Ip, Imran Niazi, Kenneth Plunkitt, Rajesh Banker, James Porterfield, James E Ip, Srinivas R Dukkipati, and LEADLESS II Study Investigators.
• From the Icahn School of Medicine at Mount Sinai (V.Y.R., S.R.D.) and Weill Cornell Medical Center (J.E.I.) - both in New York; Libin Cardiovascular Institute of Alberta, Calgary, Canada (D.V.E.); Cleveland Clinic, Cleveland (D.J.C.); Keck Hospital of University of Southern California, Los Angeles (R.D.), and Premier Cardiology, Newport Beach (R.B.) - both in California; Intermountain Medical Center Heart Institute, Salt Lake City, (T.J.B.); Central Baptist Hospital, Lexington, KY (G.F.T.); Mayo Clinic, Rochester, MN (P.A.F.); Tufts University School of Medicine, Boston (N.A.M.E.); Sparrow Clinical Research Institute, Lansing, MI (J.I.); Aurora Medical Group, Milwaukee (I.N.); Naples Community Hospital, Naples, FL (K.P.); and Methodist University Hospital, Memphis, TN (J.P.).
• N. Engl. J. Med. 2015 Sep 17;373(12):1125-35.

BackgroundCardiac pacemakers are limited by device-related complications, notably infection and problems related to pacemaker leads. We studied a miniaturized, fully self-contained leadless pacemaker that is nonsurgically implanted in the right ventricle with the use of a catheter.MethodsIn this multicenter study, we implanted an active-fixation leadless cardiac pacemaker in patients who required permanent single-chamber ventricular pacing. The primary efficacy end point 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 end point was freedom from device-related serious adverse events through 6 months. In this ongoing study, the prespecified analysis of the primary end points was performed on data from the first 300 patients who completed 6 months of follow-up (primary cohort). The rates of the efficacy end point and safety end point 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).ResultsThe leadless pacemaker was successfully implanted in 504 of the 526 patients in the total cohort (95.8%). The intention-to-treat primary efficacy end point was met in 270 of the 300 patients in the primary cohort (90.0%; 95% confidence interval [CI], 86.0 to 93.2, P=0.007), and the primary safety end point was met in 280 of the 300 patients (93.3%; 95% CI, 89.9 to 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%).ConclusionsThe leadless cardiac pacemaker met prespecified pacing and sensing requirements in the large majority of patients. Device-related serious adverse events occurred in approximately 1 in 15 patients. (Funded by St. Jude Medical; LEADLESS II ClinicalTrials.gov number, NCT02030418.).

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