title: R-wave sensing in an implantable cardiac monitor without ECG-based preimplant mapping: results from a multicenter clinical trial.
abstract: BACKGROUND
  Reducing the form factor of an implantable cardiac monitor (ICM) may simplify device implant. This study evaluated R-wave sensing at a range of electrode distances and a preferred device implant location without mapping.
  
  
  METHODS
  Patients scheduled for a Medtronic Reveal® ICM implant (Medtronic Inc., Minneapolis, MN, USA) underwent a preimplant pocket recording using a diagnostic recording catheter. The ICM implant location was left to the discretion of the implanting physician, but a "recommended" position spanned the V2 -V3 electrocardiogram electrode location in an oblique 45° angle. R-wave amplitudes were analyzed from ICM follow-up.
  
  
  RESULTS
  Seventeen of 41 subjects (15 male, age 57 ± 16 years) had the maximum surface-filtered R-wave at the recommended location. Fourteen patients underwent diagnostic recording across the range of electrode spacing. There was a strong correlation between the R-wave amplitude and electrode distance (r(2) = 0.97, P < 0.001) with an increase of 29 μV per 2.5 mm. Comparing normalized R-wave distributions between the recommended ICM implant group (Group 1, n = 19) and the remaining patients (Group 2, n = 7), the proportion of ICM R-wave counts of amplitude 0.25-1.2 mV was higher (79% vs 46%, P < 0.05). Of 17 patients in Group 1 who had ≥ 1-month ICM follow-up (79 ± 45 days), no sensing-related false arrhythmia detection was found in 16 (93%) patients.
  
  
  CONCLUSIONS
  The subcutaneous R-wave amplitude correlates with electrode spacing in the implant zone of ICM patients. Implant locations at the V2 -V3 position at a 45° angle offer an adequate R wave for sensing. Preimplant mapping to achieve acceptable R-wave amplitude may not be necessary.
authors.affiliation: Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Krahn
authors.forename: Robert A
authors.initials: RA
authors.lastname: Pickett
authors.forename: Scott
authors.initials: S
authors.lastname: Sakaguchi
authors.forename: Naushad
authors.initials: N
authors.lastname: Shaik
authors.forename: Jian
authors.initials: J
authors.lastname: Cao
authors.forename: Holly S
authors.initials: HS
authors.lastname: Norman
authors.forename: Patricia
authors.initials: P
authors.lastname: Guerrero
mesh_terms: D018780:Body Surface Potential Mapping / Q000295:instrumentation* / Q000379:methods*; D002170:Canada; D004562:Electrocardiography / Q000295:instrumentation / Q000379:methods; D015716:Electrocardiography, Ambulatory / Q000295:instrumentation* / Q000379:methods*; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D019736:Prostheses and Implants; D019919:Prosthesis Implantation / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014481:United States
keywords: ECG; R-wave sensing; implant; implantable cardiac monitor; mapping; subcutaneous