title: Electrogram-based optimal atrioventricular and interventricular delays of cardiac resynchronization change individually during exercise.
abstract: BACKGROUND
  Limited data suggest that optimal atrioventricular (AV) and interventricular (VV) delays are different at rest than during exercise in patients with heart failure. We assessed the feasibility and reproducibility of an electrogram-based method of optimization called QuickOpt at rest and during exercise.
  
  
  METHODS
  Patients with a St Jude Medical cardiac resynchronization therapy implantable cardioverter-defibrillator were subjected to a graded treadmill test, and QuickOpt was repeatedly measured prior to, during, and after the exercise.
  
  
  RESULTS
  Twenty-four patients (16 males, aged 67.4 ± 7.7 years) participated. At rest, delays (in ms) were 110.4 ± 20.1 for sensed AV delay and -70 (LV pacing first) to +20 (RV pacing first) for VV delay. The changes in QuickOpt-derived delays at rest were not significant despite change in body position. During exercise, QuickOpt-derived AV delays did not change in 11 patients, were shorter during peak exercise in 8 patients, and were longer in 3 patients (average value during peak exercise was 126.5 ± 15.8 ms, P = 0.04 compared to baseline). The QuickOpt-derived VV delay gradually shifted toward earlier right ventricular pacing during exercise in 19 patients, while no changes were seen in 3 patients, and a shift occurred toward earlier left ventricular pacing in 2 patients (average value during peak exercise was -30.7 ± 22.2; P = 0.001 compared to baseline). There was no correlation between changes in the QuickOpt-derived AV and VV delays and heart rate.
  
  
  CONCLUSIONS
  The application of electrogram-based algorithm is feasible both at rest and during exercise. The results are reproducible. QuickOpt-derived AV and VV delays individually change during exercise.
authors.affiliation: St. Michael's Hospital, Division of Cardiology, University of Toronto, Toronto, Ontario, Canada. pintera@smh.ca
authors.forename: Gregory
authors.initials: G
authors.lastname: Golovchiner
authors.forename: Paul
authors.initials: P
authors.lastname: Dorian
authors.forename: Iqwal
authors.initials: I
authors.lastname: Mangat
authors.forename: Victoria
authors.initials: V
authors.lastname: Korley
authors.forename: Kamran
authors.initials: K
authors.lastname: Ahmad
authors.forename: Khairi
authors.initials: K
authors.lastname: Sharef
authors.forename: Emoke
authors.initials: E
authors.lastname: Posan
authors.forename: Eugene
authors.initials: E
authors.lastname: Crystal
authors.forename: Suzan
authors.initials: S
authors.lastname: O'Donnell
authors.forename: Arnold
authors.initials: A
authors.lastname: Pinter
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D015331:Cohort Studies; D017147:Defibrillators, Implantable; D004562:Electrocardiography / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018709:Statistics, Nonparametric; D016277:Ventricular Function, Left / Q000502:physiology; D016278:Ventricular Function, Right / Q000502:physiology