• Dwight Reynolds, Gabor Z Duray, Razali Omar, Kyoko Soejima, Petr Neuzil, Shu Zhang, Calambur Narasimhan, Clemens Steinwender, Josep Brugada, Michael Lloyd, Paul R Roberts, Venkata Sagi, John Hummel, Maria Grazia Bongiorni, Reinoud E Knops, Christopher R Ellis, Charles C Gornick, Matthew A Bernabei, Verla Laager, Kurt Stromberg, Eric R Williams, J Harrison Hudnall, Philippe Ritter, and Micra Transcatheter Pacing Study Group.
• From the Cardiovascular Section, University of Oklahoma Health Sciences Center, OU Medical Center, Oklahoma City (D.R.); Clinical Electrophysiology Department of Cardiology, Medical Center, Hungarian Defence Forces, Budapest, Hungary (G.Z.D.); Electrophysiology and Pacing Unit, National Heart Institute, Kuala Lumpur, Malaysia (R.O.); Department of Cardiology, Kyorin University Hospital, Tokyo (K. Soejima); Department of Cardiology, Na Homolce Hospital, Prague, Czech Republic (P.N.); Clinical EP Lab and Arrhythmia Center, Fuwai Hospital, Beijing (S.Z.); Division of Electrophysiology, Department of Cardiology, CARE Hospitals and CARE Foundation, Hyderabad, India (C.N.); Department of Cardiology, Linz General Hospital, Johannes Kepler University School of Medicine, Linz, Austria (C.S.); Hospital Universitari Clínic de Barcelona, Barcelona (J.B.); Emory University Hospital, Atlanta (M.L.); University of Southampton, Southampton, United Kingdom (P.R.R.); Baptist Heart Specialists, Jacksonville, FL (V.S.); Ohio State University, Columbus (J.H.); Azienda Ospedaliero Universitaria Pisana, Presidio Ospedaliero di Cisanello, Pisa, Italy (M.G.B.); Academisch Medisch Centrum, Amsterdam (R.E.K.); Vanderbilt University Medical Center, Nashville (C.R.E.); Minneapolis Heart Institute, Minneapolis (C.C.G.); Lancaster Heart and Vascular Institute, Lancaster, PA (M.A.B.); Medtronic, Mounds View, MN (V.L., K. Stromberg, E.R.W., J.H.H.); and Hôpital Cardiologique du Haut-Lévêque, Centre Hospitalier Universitaire Bordeaux, Université Bordeaux, IHU l'Institut de Rythmologie et Modélisation Cardiaque, Bordeaux, France (P.R.).
• N. Engl. J. Med. 2016 Feb 11;374(6):533-41.

BackgroundA leadless intracardiac transcatheter pacing system has been designed to avoid the need for a pacemaker pocket and transvenous lead.MethodsIn a prospective multicenter study without controls, a transcatheter pacemaker was implanted in patients who had guideline-based indications for ventricular pacing. The analysis of the primary end points began when 300 patients reached 6 months of follow-up. The primary safety end point was freedom from system-related or procedure-related major complications. The primary efficacy end point was the percentage of patients with low and stable pacing capture thresholds at 6 months (≤2.0 V at a pulse width of 0.24 msec and an increase of ≤1.5 V from the time of implantation). The safety and efficacy end points were evaluated against performance goals (based on historical data) of 83% and 80%, respectively. We also performed a post hoc analysis in which the rates of major complications were compared with those in a control cohort of 2667 patients with transvenous pacemakers from six previously published studies.ResultsThe device was successfully implanted in 719 of 725 patients (99.2%). The Kaplan-Meier estimate of the rate of the primary safety end point was 96.0% (95% confidence interval [CI], 93.9 to 97.3; P<0.001 for the comparison with the safety performance goal of 83%); there were 28 major complications in 25 of 725 patients, and no dislodgements. The rate of the primary efficacy end point was 98.3% (95% CI, 96.1 to 99.5; P<0.001 for the comparison with the efficacy performance goal of 80%) among 292 of 297 patients with paired 6-month data. Although there were 28 major complications in 25 patients, patients with transcatheter pacemakers had significantly fewer major complications than did the control patients (hazard ratio, 0.49; 95% CI, 0.33 to 0.75; P=0.001).ConclusionsIn this historical comparison study, the transcatheter pacemaker met the prespecified safety and efficacy goals; it had a safety profile similar to that of a transvenous system while providing low and stable pacing thresholds. (Funded by Medtronic; Micra Transcatheter Pacing Study ClinicalTrials.gov number, NCT02004873.).

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