title: Improvement in coronary blood flow velocity with acute biventricular pacing is predominantly due to an increase in a diastolic backward-travelling decompression (suction) wave.
abstract: BACKGROUND
  Normal coronary blood flow is principally determined by a backward-traveling decompression (suction) wave in diastole. Dyssynchronous chronic heart failure may attenuate suction, because regional relaxation and contraction overlap in timing. We hypothesized that biventricular pacing, by restoring left ventricular (LV) synchronization and improving LV relaxation, might increase this suction wave, improving coronary flow.
  
  
  RESULTS
  Ten patients with chronic heart failure (9 males; age 65±12; ejection fraction 26±7%) with left bundle-branch block (LBBB; QRS duration 174±18 ms) were atriobiventricularly paced at 100 bpm. LV pressure was measured and wave intensity calculated from invasive coronary flow velocity and pressure, with native conduction (LBBB) and during biventricular pacing at atrioventricular (AV) delays of 40 ms, 120 ms, and separately preidentified hemodynamically optimal AV delay. In comparison with LBBB, biventricular pacing at separately preidentified hemodynamically optimal AV delay (BiV-Opt) enhanced coronary flow velocity time integral by 15% (7%-25%) (P=0.007), LV dP/dt(max) by 15% (10%-21%) (P=0.005), and (neg)dP/dt(max) by 17% (9%-22%) (P=0.005). The cumulative intensity of the diastolic backward decompression (suction) wave increased by 26% (18%-54%) (P=0.005). The majority of the increase in coronary flow velocity time integral occurred in diastole (69% [41%-84% ]; P=0.047). The systolic compression waves also increased: forward by 36% (6%-49%) (P=0.022) and backward by 38% (20%-55%) (P=0.022). Biventricular pacing at AV delays of 120 ms generated a smaller LV dP/dt(max) (by 12% [5%-23% ], P=0.013) and (neg)dP/dt(max) (by 15% [8%-40% ]; P=0.009) increase than BiV-Opt, against LBBB as reference; BiV-Opt and biventricular pacing at AV delays of 120 ms were not significantly different in coronary flow velocity time integral or waves. Biventricular pacing at AV delays of 40 ms was no different from LBBB.
  
  
  CONCLUSIONS
  When biventricular pacing improves LV contraction and relaxation, it increases coronary blood flow velocity, predominantly by increasing the dominant diastolic backward decompression (suction) wave.
authors.affiliation: International Centre for Circulatory Health, St. Mary's Hospital and Imperial College, 59-61 North Wharf Road, W2 1LA, United Kingdom. andreas.kyriacou@imperial.ac.uk
authors.forename: Andreas
authors.initials: A
authors.lastname: Kyriacou
authors.forename: Zachary I
authors.initials: ZI
authors.lastname: Whinnett
authors.forename: Sayan
authors.initials: S
authors.lastname: Sen
authors.forename: Punam A
authors.initials: PA
authors.lastname: Pabari
authors.forename: Ian
authors.initials: I
authors.lastname: Wright
authors.forename: Richard
authors.initials: R
authors.lastname: Cornelussen
authors.forename: David
authors.initials: D
authors.lastname: Lefroy
authors.forename: D Wyn
authors.initials: DW
authors.lastname: Davies
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Peters
authors.forename: Prapa
authors.initials: P
authors.lastname: Kanagaratnam
authors.forename: Jamil
authors.initials: J
authors.lastname: Mayet
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.forename: Justin E
authors.initials: JE
authors.lastname: Davies
mesh_terms: D000368:Aged; D001283:Atrioventricular Node / Q000503:physiopathology; D001783:Blood Flow Velocity / Q000502:physiology; D058406:Cardiac Resynchronization Therapy; D003331:Coronary Vessels / Q000503:physiopathology*; D003971:Diastole / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology / Q000628:therapy