title: Accelerometer-derived time intervals during various pacing modes in patients with biventricular pacemakers: comparison with normals.
abstract: BACKGROUND
  Changes due to biventricular pacing have been documented by shortening of QRS duration and echocardiography. Compared to normal ventricular activation, the presence of left bundle branch block (LBBB) results in a significant change in cardiac cycle time intervals. Some of these have been used to quantify the underlying cardiac dyssynchrony, assess the effects of biventricular pacing, and guide programming of ventricular pacing devices. This study evaluates a simple noninvasive method using accelerometers attached to the skin to measure cardiac time intervals in biventricularly paced patients.
  
  
  METHODS
  Ten patients with biventricular pacemakers previously implanted for congestive heart failure were paced in the AAI mode, then in atrioventricular (AV) sequential mode from the right and left ventricles followed by biventricular pacing. Simultaneous recordings were obtained by 2D, Doppler echocardiography as well as by accelerometers. Similar recordings were obtained from 10 gender, aged matched, normal controls during sinus rhythm.
  
  
  RESULTS
  Compared to normals, heart failure patients paced in AAI mode had prolonged isovolumetric contraction time (IVCT), shorter ventricular ejection time (LVET), and prolonged isovolumetric relaxation (IVRT). With biventricular pacing the IVCT decreased, but the LVET and IVRT did not change significantly. There was excellent correlation between the echo and accelerometer-measured intervals.
  
  
  CONCLUSIONS
  Shortening of the IVCT measured by an accelerometer is a consistent time interval change due to biventricular pacing that probably reflects more rapid acceleration of left ventricular ejection. The accelerometer may be useful to assess immediate efficacy of biventricular pacing during device implantation and optimize programmable time intervals such as AV and interventricular (VV) delays.
authors: University Medical Center, Sarver Heart Center, Tucson, AZ 85724, USA. fmarcus@u.arizona.edu
authors: Frank I
authors: FI
authors: Marcus
authors: Vincent
authors: V
authors: Sorrell
authors: John
authors: J
authors: Zanetti
authors: Mike
authors: M
authors: Bosnos
authors: Gurpreet
authors: G
authors: Baweja
authors: Doug
authors: D
authors: Perlick
authors: Peter
authors: P
authors: Ott
authors: Julia
authors: J
authors: Indik
authors: Ding Sheng
authors: DS
authors: He
authors: Kathy
authors: K
authors: Gear
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D016022:Case-Control Studies; D004562:Electrocardiography; D004867:Equipment Design; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013997:Time Factors; D016896:Treatment Outcome