title: The atrioventricular delay of cardiac resynchronization can be optimized hemodynamically during exercise and predicted from resting measurements.
abstract: BACKGROUND
  Atrioventricular (AV) optimization of cardiac resynchronization therapy (CRT) is typically calculated at rest. However, patients often become symptomatic during exercise.
  
  
  OBJECTIVE
  In this study, we use acute noninvasive hemodynamics to optimize the AV delay of CRT during exercise and investigate whether this exercise optimum can be predicted from a three-phase resting model.
  
  
  METHODS
  In 20 patients with CRT, we adjusted the sensed AV delay while the patient exercised on a treadmill up to a heart rate of 100 bpm to identify the hemodynamically optimal value. Separately, at rest, by pacing with three different configurations and calculating the sensed-paced difference, we calculated an "expected" value for the exercise optimum.
  
  
  RESULTS
  It was possible to perform AV delay optimization while a patient exercised. The resting three-phase model correlated well with the actual exercise optimal AV delay (r = 0.85, mean difference +/- standard deviation [SD] = 3.7 +/- 17 ms). Simply using measurements made at rest during atrial-sensed pacing showed a poorer correlation with exercise (r = 0.64, mean difference +/- SD = 2.2 +/- 24 ms). The three-phase resting model allows improved exercise hemodynamics to be achieved. Programming according to the three-phase resting model yields an exercise blood pressure of only 0.5 mmHg (+/-1.4 mmHg; P = NS) less than the true exercise optimum, whereas programming the resting sensed optimum yields an exercise blood pressure of 1.4 mmHg (+/-2.2 mmHg, P = .02) less than the true optimum.
  
  
  CONCLUSIONS
  Using acute noninvasive hemodynamics and a protocol of alternations, it is possible to optimize the AV delay of cardiac resynchronization devices even while a patient exercises. In clinical practice, the exercise optimum AV delay could be determined from three phases of resting measurements, without performing exercise.
authors.affiliation: International Centre for Circulatory Health, St. Mary's Hospital and Imperial College, London, United Kingdom. zacharywhinnett@yahoo.com
authors.forename: Zachary I
authors.initials: ZI
authors.lastname: Whinnett
authors.forename: Cathy
authors.initials: C
authors.lastname: Briscoe
authors.forename: Justin E R
authors.initials: JE
authors.lastname: Davies
authors.forename: Keith
authors.initials: K
authors.lastname: Willson
authors.forename: Charlotte H
authors.initials: CH
authors.lastname: Manisty
authors.forename: D Wyn
authors.initials: DW
authors.lastname: Davies
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Peters
authors.forename: Prapa
authors.initials: P
authors.lastname: Kanagaratnam
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
authors.forename: Jamil
authors.initials: J
authors.lastname: Mayet
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
mesh_terms: D001283:Atrioventricular Node / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D016009:Chi-Square Distribution; D017147:Defibrillators, Implantable; D015444:Exercise; D006339:Heart Rate / Q000502:physiology*; D006439:Hemodynamics; D006801:Humans; D011237:Predictive Value of Tests; D012146:Rest