title: Long-term outcomes in leadless Micra transcatheter pacemakers with elevated thresholds at implantation: Results from the Micra Transcatheter Pacing System Global Clinical Trial.
abstract: Device repositioning during Micra leadless pacemaker implantation may be required to achieve optimal pacing thresholds.
  
  
  
  The purpose of this study was to describe the natural history of acute elevated Micra vs traditional transvenous lead thresholds.
  
  
  
  Micra study VVI patients with threshold data (at 0.24 ms) at implant (n = 711) were compared with Capture study patients with de novo transvenous leads at 0.4 ms (n = 538). In both cohorts, high thresholds were defined as >1.0 V and very high as >1.5 V. Change in pacing threshold (0-6 months) with high (1.0 to ≤1.5 V) or very high (>1.5 V) thresholds were compared using the Wilcoxon signed-rank test.
  
  
  
  Of the 711 Micra patients, 83 (11.7%) had an implant threshold of >1.0 V at 0.24 ms. Of the 538 Capture patients, 50 (9.3%) had an implant threshold of >1.0 V at 0.40 ms. There were no significant differences in patient characteristics between those with and without an implant threshold of >1.0 V, with the exception of left ventricular ejection fraction in the Capture cohort (high vs low thresholds, 53% vs 58%; P = .011). Patients with an implant threshold of >1.0 V decreased significantly (P < .001) in both cohorts. Micra patients with high and very high thresholds decreased significantly (P < .01) by 1 month, with 87% and 85% having 6-month thresholds lower than the implant value. However, when the capture threshold at implant was >2 V, only 18.2% had a threshold of ≤1 V at 6 months and 45.5% had a capture threshold of >2 V.
  
  
  
  Pacing thresholds in most Micra patients with elevated thresholds decrease after implant. Micra device repositioning may not be necessary if the pacing threshold is ≤2 V.
authors.affiliation: Duke University Medical Center, Durham, North Carolina. Electronic address: jonathan.piccini@duke.edu.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Piccini
authors.affiliation: Medtronic plc, Mounds View, Minnesota.
authors.forename: Kurt
authors.initials: K
authors.lastname: Stromberg
authors.affiliation: Duke University Medical Center, Durham, North Carolina.
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Jackson
authors.affiliation: Medtronic plc, Mounds View, Minnesota.
authors.forename: Verla
authors.initials: V
authors.lastname: Laager
authors.affiliation: Clinical Electrophysiology, Department of Cardiology, Medical Centre, Hungarian Defence Forces, Budapest, Hungary.
authors.forename: Gabor Z
authors.initials: GZ
authors.lastname: Duray
authors.affiliation: Emory University Hospital, Atlanta, Georgia.
authors.forename: Mikhael
authors.initials: M
authors.lastname: El-Chami
authors.affiliation: Vanderbilt University Medical Center, Nashville, Tennessee.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Ellis
authors.affiliation: Ohio State University, Columbus, Ohio.
authors.forename: John
authors.initials: J
authors.lastname: Hummel
authors.affiliation: Providence Health & Services, Portland, Oregon.
authors.forename: D Randy
authors.initials: DR
authors.lastname: Jones
authors.affiliation: BHVH at Baylor University Medical Center, Dallas, Texas.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Kowal
authors.affiliation: CARE Hospitals, CARE Foundation, Hyderabad India.
authors.forename: Calambur
authors.initials: C
authors.lastname: Narasimhan
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: University of Southampton, Southampton, United Kingdom.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Roberts
authors.affiliation: Department of Cardiology, Kyorin University Hospital, Tokyo, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Soejima
authors.affiliation: Clinical EP Lab and Arrhythmia Center, Fuwai Hospital, Beijing, China.
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
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
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001919:Bradycardia / Q000503:physiopathology / Q000628:therapy*; D062906:Cardiac Catheters; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004056:Differential Threshold; D004562:Electrocardiography; D004567:Electrodes, Implanted; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D016896:Treatment Outcome
keywords: Bradycardia; Capture threshold; Clinical trial; Leadless pacemaker; Outcomes; Pacemaker; VVI