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Long-term outcomes in leadless Micra transcatheter pacemakers with elevated thresholds at implantation: Results from the Micra Transcatheter Pacing System Global Clinical Trial

Piccini JP 1 , Stromberg K 2 , Jackson KP 3 , Laager V 2 , Duray GZ 4 , El-Chami M 5 Show all authors , Ellis CR 6 , Hummel J 7 , Jones DR 8 , Kowal RC 9 , Narasimhan C 10 , Omar R 11 , Ritter P 12 , Roberts PR 13 , Soejima K 14 , Zhang S 15 , Reynolds D 16 , Micra Transcatheter Pacing Study Group

Affiliations 

  • 1 Duke University Medical Center, Durham, North Carolina. Electronic address: [email protected]
  • 2 Medtronic plc, Mounds View, Minnesota
  • 3 Duke University Medical Center, Durham, North Carolina
  • 4 Clinical Electrophysiology, Department of Cardiology, Medical Centre, Hungarian Defence Forces, Budapest, Hungary
  • 5 Emory University Hospital, Atlanta, Georgia
  • 6 Vanderbilt University Medical Center, Nashville, Tennessee
  • 7 Ohio State University, Columbus, Ohio
  • 8 Providence Health & Services, Portland, Oregon
  • 9 BHVH at Baylor University Medical Center, Dallas, Texas
  • 10 CARE Hospitals, CARE Foundation, Hyderabad India
  • 11 Electrophysiology and Pacing Unit, National Heart Institute, Kuala Lumpur, Malaysia
  • 12 Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, Université Bordeaux, IHU LIRYC, Bordeaux, France
  • 13 University of Southampton, Southampton, United Kingdom
  • 14 Department of Cardiology, Kyorin University Hospital, Tokyo, Japan
  • 15 Clinical EP Lab and Arrhythmia Center, Fuwai Hospital, Beijing, China
  • 16 Cardiovascular Section, University of Oklahoma Health Sciences Center, OU Medical Center, Oklahoma City, Oklahoma
Heart Rhythm, 2017 05;14(5):685-691.
PMID: 28111349 DOI: 10.1016/j.hrthm.2017.01.026

Abstract

BACKGROUND: Device repositioning during Micra leadless pacemaker implantation may be required to achieve optimal pacing thresholds.

OBJECTIVE: The purpose of this study was to describe the natural history of acute elevated Micra vs traditional transvenous lead thresholds.

METHODS: 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.

RESULTS: 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.

CONCLUSIONS: 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.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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