title: Submuscular implantation of insertable cardiac monitors improves the reliability of detection of atrial fibrillation.
abstract: OBJECTIVE
  Diagnosing atrial fibrillation (AF) is highly relevant, as specific secondary prevention is of high importance. Recently, insertable cardiac monitors (ICMs) have been introduced for continuous monitoring to detect asymptomatic episodes of AF. The detection of AF remains challenging due to a relevant incidence of artifacts. This study aimed to compare the effectivity of ICM when placed in a subcutaneous or in a submuscular localization, respectively.
  
  
  METHODS
  We retrospectively analyzed data from 30 patients undergoing pulmonary vein isolation (PVI) for AF and consecutive ICM implantation. ICMs were implanted in two locations: either subcutaneously and parasternally (SC) or under the left major pectoral muscle (SP). Interrogations were continuously retrieved using remote monitoring and during repeated visits in our outpatient clinic. The transmission protocols were scanned for detected AF, and it was ruled by two blinded investigators, if detection was correct or incorrect.
  
  
  RESULTS
  Mean age was 67 ± 10 years, 56% men, 50% paroxysmal AF. In 14 of the patients, the ICM was implanted at a SC localization and in 16 patients subpectorally. R-wave amplitude was significantly higher in patents with SP implantation. There were 670 transmitted protocols including 1024 episodes detected as AF. Of these, 54% were correctly recognized as AF in the SC group. In the SP group, 85% of the recorded episodes were correctly recognized as AF (p = 0.03). The remaining episodes in both groups showed sinus rhythm with misinterpreted artifacts.
  
  
  CONCLUSIONS
  To improve effectiveness of detecting AF episodes, it is useful to implant subpectorally.
authors.affiliation: Department of Cardiology and Pneumology, Division of Clinical Electrophysiology, Heart Center, University Medical Center, Robert-Koch-Strasse 40, 37075, Göttingen, Germany, leonard.bergau@med.uni-goettingen.de.
authors.forename: Leonard
authors.initials: L
authors.lastname: Bergau
authors.forename: Christian
authors.initials: C
authors.lastname: Sohns
authors.forename: Samuel
authors.initials: S
authors.lastname: Sossalla
authors.forename: Pascal
authors.initials: P
authors.lastname: Muñoz-Exposito
authors.forename: Lars
authors.initials: L
authors.lastname: Luethje
authors.forename: Markus
authors.initials: M
authors.lastname: Zabel
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D015331:Cohort Studies; D017147:Defibrillators, Implantable; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation; D015588:Observer Variation; D010369:Pectoralis Muscles; D012008:Recurrence; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D040521:Subcutaneous Tissue; D016896:Treatment Outcome