title: Fully automatable, reproducible, noninvasive simple plethysmographic optimization: proof of concept and potential for implantability.
abstract: BACKGROUND
  Hemodynamic optimization of cardiac resynchronization therapy (CRT) can be achieved reproducibly and--with bulky, nonimplantable equipment--noninvasively. We explored whether a simple photoplethysmogram signal might be used instead.
  
  
  METHODS
  Twenty patients (age 65 ± 12) with CRT underwent automatic atrioventricular (AV) delay optimization, using a multiple-transitions protocol, at two atrially paced heart rates: just above sinus rate ("slow ApVp," 77 ± 11 beats per minute [bpm]) and 100 bpm ("fast ApVp"). We then retested to assess short-term reproducibility.
  
  
  RESULTS
  All 80 optimizations identified an optimum (correctly oriented parabola). At 100 bpm, the simple photoplethysmogram had wider scatter between repeat optimizations than did Finometer: standard deviation of difference (SDD) 22 ms versus 14 ms, respectively, P = 0.028. The simple photoplethysmogram improved in reproducibility when slope (instead of peak) of its signal was used for optimization, becoming as reproducible as Finometer (SDD 14 ms vs 14 ms, P = 0.50). At slow heart rate, reproducibility of simple photoplethysmogram-based optimization worsened from 14 to 22 ms (P = 0.028), and Finometer-based optimization from 14 to 26 ms (P = 0.005). Increasing the number of replicates averaged improved reproducibility. For example, SDD of simple photoplethysmogram optimization (using peak) fell from 62 ms with two replicates to 22 ms with eight replicates (P < 0.0001). At 100 bpm, the eight-replicate protocol takes ∼12 minutes.
  
  
  CONCLUSIONS
  A 12-minute protocol of simple photoplethysmographic AV optimization can be processed fully automatically. Blinded test-retest reproducibility of the optimum AV is good and improves with more replicates. If benefits to some patients are not to be neutralized by harm to others, endpoint studies should first test check narrowness of "within-patient error bars."
authors: International Centre for Circulatory Health, St. Mary's Hospital and Imperial College, London, United Kingdom. andreas.kyriacou@imperial.ac.uk
authors: Andreas
authors: A
authors: Kyriacou
authors: Punam A
authors: PA
authors: Pabari
authors: Zachary I
authors: ZI
authors: Whinnett
authors: Satpal
authors: S
authors: Arri
authors: Keith
authors: K
authors: Willson
authors: Resham
authors: R
authors: Baruah
authors: Berthold
authors: B
authors: Stegemann
authors: Jamil
authors: J
authors: Mayet
authors: Prapa
authors: P
authors: Kanagaratnam
authors: Alun D
authors: AD
authors: Hughes
authors: Darrel P
authors: DP
authors: Francis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D017147:Defibrillators, Implantable; D005260:Female; D006333:Heart Failure / Q000628:therapy; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000295:instrumentation / Q000379:methods; D017156:Photoplethysmography / Q000295:instrumentation / Q000379:methods*; D012720:Severity of Illness Index; D016896:Treatment Outcome