title: Beat-to-beat effects of intraaortic balloon pump timing on left ventricular performance in patients with low ejection fraction.
abstract: BACKGROUND
  Intraaortic balloon counterpulsation (IABP) timing errors during arrhythmia may result in afterload increases which may negatively influence left ventricular (LV) ejection and LV mechanical dyssynchrony. The aim of our study was to determine beat-to-beat effects of properly timed IABP, premature IAB inflation, and late IAB deflation on LV performance and LV mechanical dyssynchrony in heart failure patients undergoing cardiac surgery.
  
  
  METHODS
  In 15 patients, LV pressure-volume relations and LV dyssynchrony were measured by conductance volume catheter. Properly timed IABP was evaluated at a 1:1 assist ratio within a 10 seconds time-span. Premature IAB inflation and late IAB deflation were evaluated at a 1:4 assist ratio.
  
  
  RESULTS
  Properly timed 1:1 IABP acutely decreased LV end-systolic volume by 6.1% (p < 0.0001) and LV end-systolic pressure by 17.5% (p < 0.0001) due to decreased aortic impedance. Stroke volume (SV) increased by 14% (p < 0.0001), which correlated markedly with a decrease of LV mechanical dyssynchrony (p < 0.0001). The largest SV increases occurred in patients with lowest contractile state. Premature IAB inflation decreased SV by 20% (p < 0.0001) due to abrupt increase of LV afterload during late ejection. Late IAB deflation increased SV and stroke work by 18% (p < 0.0001) and 16% (p < 0.01) respectively, due to increased afterload during early ejection and decreased afterload during late ejection.
  
  
  CONCLUSIONS
  Left ventricular performance during IABP is causally related to changes in LV afterload, and the timing of these changes in relation to contraction or relaxation phases, to LV mechanical dyssynchrony and to contractile state.
authors.affiliation: Department of Cardiac Surgery, San Raffaele University Hospital, Milan, Italy. schreuder@libero.it
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Schreuder
authors.forename: Francesco
authors.initials: F
authors.lastname: Maisano
authors.forename: Andrea
authors.initials: A
authors.lastname: Donelli
authors.forename: Jos R C
authors.initials: JR
authors.lastname: Jansen
authors.forename: Pat
authors.initials: P
authors.lastname: Hanlon
authors.forename: Jan
authors.initials: J
authors.lastname: Bovelander
authors.forename: Ottavio
authors.initials: O
authors.lastname: Alfieri
mesh_terms: D006801:Humans; D007423:Intra-Aortic Balloon Pumping; D008875:Middle Aged; D013318:Stroke Volume; D013997:Time Factors; D016277:Ventricular Function, Left