title: Novel use of cardiac pacemakers in heart failure to dynamically manipulate the respiratory system through algorithmic changes in cardiac output.
abstract: BACKGROUND
  Alternation of heart rate between 2 values using a pacemaker generates oscillations in end-tidal CO(2) (et-CO(2)). This study examined (a) whether modulating atrioventricular delay can also do this, and (b) whether more gradual variation of cardiac output can achieve comparable changes in et-CO(2) with less-sudden changes in blood pressure.
  
  
  RESULTS
  We applied pacemaker fluctuations by adjusting heart rate (by 30 bpm) or atrioventricular delay (between optimal and nonoptimal values) or both, with period of 60 s in 19 heart failure patients (age 73+/-11, EF 29+/-12%). The changes in cardiac output, by either heart rate or atrioventricular delay or both, were made either as a step ("square wave") or more gradually ("sine wave"). We obtained changes in cardiac output sufficient to engender comparable oscillations in et-CO(2) (P=NS) in all 19 patients either by manipulation of heart rate (14), or by atrioventricular delay (2) or both (3). The square wave produced 191% larger and 250% more sudden changes in blood pressure than the sine wave alternations (22.4+/-11.7 versus 13.6+/-4.5 mm Hg, P<0.01 and 19.8+/-10.0 versus 7.9+/-3.2 mm Hg over 5 s, P<0.01), but peak-to-trough et-CO(2) elicited was only 45% higher (0.45+/-0.18 versus 0.31+/-0.13 kPa, P=0.01).
  
  
  CONCLUSIONS
  This study shows that cardiac output is the key to dynamically manipulating the respiratory system with pacing sequences. When manipulating respiration by this route, a sine wave pattern may be preferable to a square wave, because it minimizes sudden blood pressure fluctuations.
authors.affiliation: International Centre for Circulatory Health, St Mary's Hospital and Imperial College, London, United Kingdom. rb98@doctors.org.uk
authors.forename: Resham
authors.initials: R
authors.lastname: Baruah
authors.forename: Charlotte H
authors.initials: CH
authors.lastname: Manisty
authors.forename: Alberto
authors.initials: A
authors.lastname: Giannoni
authors.forename: Keith
authors.initials: K
authors.lastname: Willson
authors.forename: Yoseph
authors.initials: Y
authors.lastname: Mebrate
authors.forename: A John
authors.initials: AJ
authors.lastname: Baksi
authors.forename: Beth
authors.initials: B
authors.lastname: Unsworth
authors.forename: Nearchos
authors.initials: N
authors.lastname: Hadjiloizou
authors.forename: Richard
authors.initials: R
authors.lastname: Sutton
authors.forename: Jamil
authors.initials: J
authors.lastname: Mayet
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001283:Atrioventricular Node / Q000503:physiopathology*; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000378:metabolism; D002302:Cardiac Output; D002304:Cardiac Pacing, Artificial; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D012123:Pulmonary Ventilation; D012119:Respiration; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide