title: Ventricular high-rate episodes in pacemaker diagnostics identify a high-risk subgroup of patients with tachy-brady syndrome.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the frequency and clinical significance of ventricular high-rate (VHR) episodes (ventricular rate >162 bpm) in patients with symptomatic bradycardia and paroxysmal atrial fibrillation (AF).
  
  
  BACKGROUND
  Newer pacemakers have enhanced diagnostic features that permit detection and storage of detailed information about the frequency, duration, and time of onset of multiple episodes of AF, atrial tachycardia (AT), and ventricular tachycardia (VT). However, the prevalence and prognostic value of AF associated with rapid ventricular rates in the pacemaker population are unknown.
  
  
  METHODS
  We prospectively followed 125 patients who received a Medtronic AT 500/501 pacemaker for symptomatic bradycardia and paroxysmal AF.
  
  
  RESULTS
  AF recurred in 112 patients (90%) during 22 +/- 8 months of follow-up. A total of 1,324 VHR episodes occurred in 38 patients (30%). Episodes with available electrograms (n = 560) were reviewed and classified as AF (n = 279; 50%), AT (n = 266; 47%) or VT (n = 15; 3%). AF burden was higher in patients with VHR episodes (median 1.9 vs 0.2 hours/day; P < .001). After controlling for AT/AF burden and heart disease, VHR episodes were a significant independent predictor of hospitalization for cardiovascular symptoms (odds ratio 2.92, 95% confidence interval 1.33-6.38; P = .007). Heart rate control improved over time in the cohort, and the frequency of VHR episodes decreased during follow-up (P < .001).
  
  
  CONCLUSIONS
  VHR episodes documented in the pacemaker diagnostics identify a high-risk subgroup of patients with AF. Monitoring VHR episodes may be useful for identifying pacemaker patients with AF who require more vigilant monitoring, additional investigations, and/or additional interventions.
authors.affiliation: Department of Cardiac Sciences and Department of Community Medicine, University of Calgary, Alberta, Canada.
authors.forename: Rik
authors.initials: R
authors.lastname: Willems
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Morck
authors.forename: Derek V
authors.initials: DV
authors.lastname: Exner
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Rose
authors.forename: Anne M
authors.initials: AM
authors.lastname: Gillis
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000453:epidemiology / Q000503:physiopathology*; D001919:Bradycardia / Q000503:physiopathology / Q000628:therapy*; D017147:Defibrillators, Implantable; D005260:Female; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011379:Prognosis; D011446:Prospective Studies; D011475:Prosthesis Failure; D012008:Recurrence; D012307:Risk Factors; D013577:Syndrome; D013612:Tachycardia, Ectopic Atrial / Q000453:epidemiology / Q000503:physiopathology*; D013614:Tachycardia, Paroxysmal / Q000503:physiopathology / Q000628:therapy*