title: Rate adaptive pacing in an intracardiac pacemaker.
abstract: The Micra transcatheter pacemaker was designed to have similar functionality to conventional transvenous VVIR pacing systems. It provides rate adaptive pacing using a programmable 3-axis accelerometer designed to detect patient activity in the presence of cardiac motion.
  
  
  
  The purpose of this study was to evaluate the system's performance during treadmill tests to maximum exertion in a subset of patients within the Micra Transcatheter Pacing Study.
  
  
  
  Patients underwent treadmill testing at 3 or 6 months postimplant with algorithm programming at physician discretion. Normalized sensor rate (SenR) relative to the programmed upper sensor rate was modeled as a function of normalized workload in metabolic equivalents (METS) relative to maximum METS achieved during the test. A normalized METS and SenR were determined at the end of each 1-minute treadmill stage. The proportionality of SenR to workload was evaluated by comparing the slope from this relationship to the prospectively defined tolerance margin (0.65-1.35).
  
  
  
  A total of 69 treadmill tests were attempted by 42 patients at 3 and 6 months postimplant. Thirty tests from 20 patients who completed ≥4 stages with an average slope of 0.86 (90% confidence interval 0.77-0.96) confirmed proportionality to workload. On an individual test basis, 25 of 30 point estimates (83.3%) had a normalized slope within the defined tolerance range (range 0.46-1.08).
  
  
  
  Accelerometer-based rate adaptive pacing was proportional to workload, thus confirming rate adaptive pacing commensurate to workload is achievable with an entirely intracardiac pacing system.
authors.affiliation: Emory University Hospital, Atlanta, Georgia. Electronic address: mlloyd2@emory.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Lloyd
authors.affiliation: Cardiovascular Section, University of Oklahoma Health Sciences Center, OU Medical Center, Oklahoma City, Oklahoma.
authors.forename: Dwight
authors.initials: D
authors.lastname: Reynolds
authors.affiliation: Medtronic, plc, Mounds View, Minnesota.
authors.forename: Todd
authors.initials: T
authors.lastname: Sheldon
authors.affiliation: Medtronic, plc, Mounds View, Minnesota.
authors.forename: Kurt
authors.initials: K
authors.lastname: Stromberg
authors.affiliation: Medtronic, plc, Mounds View, Minnesota.
authors.forename: J Harrison
authors.initials: JH
authors.lastname: Hudnall
authors.affiliation: Medtronic, plc, Mounds View, Minnesota.
authors.forename: Wade M
authors.initials: WM
authors.lastname: Demmer
authors.affiliation: Electrophysiology and Pacing Unit, National Heart Institute, Kuala Lumpur, Malaysia.
authors.forename: Razali
authors.initials: R
authors.lastname: Omar
authors.affiliation: Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université Bordeaux, IHU LIRYC, Bordeaux, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Ritter
authors.affiliation: Ohio State University, Columbus, Ohio.
authors.forename: John
authors.initials: J
authors.lastname: Hummel
authors.affiliation: Hospital Clínic, Universitat de Barcelona, Catalonia, Spain.
authors.forename: Lluís
authors.initials: L
authors.lastname: Mont
authors.affiliation: Department of Cardiology, Johannes Kepler University Hospital Linz, Linz, Austria.
authors.forename: Clemens
authors.initials: C
authors.lastname: Steinwender
authors.affiliation: Clinical Electrophysiology Department of Cardiology, Medical Centre, Hungarian Defence Forces, Budapest, Hungary.
authors.forename: Gabor Z
authors.initials: GZ
authors.lastname: Duray
mesh_terms: D000368:Aged; D000465:Algorithms; D001145:Arrhythmias, Cardiac / Q000628:therapy; D062906:Cardiac Catheters; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004867:Equipment Design; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008422:Materials Testing / Q000379:methods; D055686:Metabolic Equivalent / Q000502:physiology; D008875:Middle Aged; D010138:Pacemaker, Artificial
keywords: Accelerometer; Intracardiac pacemaker; Leadless pacemaker; Rate adaptive; Rate response