title: Cardiac resynchronization therapy during rest and exercise: comparison of two optimization methods.
abstract: OBJECTIVE
  Optimal exercise programming of cardiac resynchronization therapy (CRT) devices is unknown. We aimed to: (i) investigate variations in optimal atrioventricular (AV) and interventricular (VV) delays from rest to exercise, assessed by both echocardiography and an automated intracardiac electrogram (IEGM) method; (ii) evaluate the acute haemodynamic impact of CRT optimization performed during exercise.
  
  
  RESULTS
  Twenty-four heart failure patients, previously implanted with a CRT defibrillator, underwent AV and VV delay optimization, by echocardiography and IEGM methods, both at rest and during supine bicycle exercise. Rest-to-exercise variations in optimal VV delay were observed in 58% of patients. Conversely, optimal AV delay did not change during exercise compared with rest. Substantial agreement of AV and VV delays was observed between both the optimization methods. Exercise optimization of VV delay by either method improved intraventricular dyssynchrony and increased aortic velocity time integral compared with the resting setting (P < 0.001).
  
  
  CONCLUSIONS
  In patients implanted with a CRT device, optimal VV delay varied considerably from rest to exercise, while AV delay did not change. Re-assessment of the optimal pacing configuration during supine exercise, by echocardiography as well as IEGM methods, yielded an additional haemodynamic benefit to that provided by resting optimization.
authors.affiliation: Department of Medicine, Division of Cardiology, Karolinska Institutet, Stockholm, Sweden. cinzia.valzania2@studio.unibo.it
authors.forename: Cinzia
authors.initials: C
authors.lastname: Valzania
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Eriksson
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boriani
authors.forename: Fredrik
authors.initials: F
authors.lastname: Gadler