title: Determination of optimal atrioventricular delay for cardiac resynchronization therapy using acute non-invasive blood pressure.
abstract: OBJECTIVE
  In this study, we apply non-invasive blood pressure (BP) monitoring, by continuous finger photoplethysmography (Finometer), to detect directly haemodynamic responses during adjustment of the atrioventricular (AV) delay of cardiac resynchronization therapy (CRT), at different heart rates.
  
  
  RESULTS
  Twelve patients were studied with six re-attending for reproducibility assessment. At each AV delay, systolic BP relative to a reference AV delay of 120 ms (SBPrel) was calculated. We found that at higher heart rates, altering the AV delay had a more pronounced effect on BP (average range of SBPrel=17.4 mmHg) compared with resting rates (average range of SBPrel=6.5 mmHg), P<0.0001. Secondly, peak AV delay differed between patients (minimum 120 ms, maximum 200 ms). Thirdly, small changes in AV delay had significant BP effects: programming AV delay 40 ms below the peak AV delay reduced SBPrel by 4.9 mmHg (P<0.003); having it 40 ms above the peak decreased SBPrel by 4.4 mmHg (P<0.0005). Finally, the peak AV delay is highly reproducible both on the same day and at 3 months (Bland-Altman difference: 3+/-8 ms).
  
  
  CONCLUSIONS
  Continuous non-invasive arterial pressure monitoring demonstrates that even small changes in AV delay from its haemodynamic peak value have a significant effect on BP. This peak varies between individuals, is highly reproducible, and is more pronounced at higher heart rates than resting rates.
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, St Mary's Hospital and Imperial College, 5, 9-61 North Wharf Road, London W2 1LA, UK. zacharywhinnett@yahoo.com
authors.forename: Zachary I
authors.initials: ZI
authors.lastname: Whinnett
authors.forename: Justin E R
authors.initials: JE
authors.lastname: Davies
authors.forename: Keith
authors.initials: K
authors.lastname: Willson
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Chow
authors.forename: Rodney A
authors.initials: RA
authors.lastname: Foale
authors.forename: D Wyn
authors.initials: DW
authors.lastname: Davies
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.forename: Jamil
authors.initials: J
authors.lastname: Mayet
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001283:Atrioventricular Node / Q000503:physiopathology*; D001794:Blood Pressure / Q000502:physiology*; D002037:Bundle-Branch Block / Q000503:physiopathology / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004452:Echocardiography; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D016896:Treatment Outcome