Improvement in Coronary Blood Flow Velocity with Acute Biventricular Pacing is Predominantly Due to an Increase in a Diastolic Backward-Travelling Decompression (Suction) Wave
Background—Normal coronary blood flow is principally determined by a backward-travelling decompression (suction) wave in diastole. Dyssynchronous chronic heart failure may attenuate suction, as 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.
Method and Results—Ten CHF patients (9 male; age 65±12; EF 26±7%) with left bundle branch block (LBBB, QRS duration 174±18 ms) were atrio-biventricularly paced at 100bpm. 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 40ms (BiV-40), 120ms (BiV-120), and separately pre-identified haemodynamically-optimal AV delay (BiV-Opt). Compared against LBBB, BiV-Opt enhanced coronary flow VTI by 15(7-25)% (p=0.007), LV dP/dtmax by 17(9-22)% (p=0.005) and negdP/dtmax 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 VTI 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). BiV-120 generated a smaller LV dP/dtmax (by 12(5-23)%, p=0.013) and negdP/dtmax (by 15(8-40)%, p=0.009) increase than BiV-OPT, against LBBB as reference; BiV-Opt and BiV-120 were not significantly different in coronary flow VTI or waves. BiV-40 was no different from LBBB.
Conclusions—When biventricular pacing improves left ventricular contraction and relaxation, it increases coronary blood flow velocity, predominantly by increasing the dominant diastolic backward decompression (suction) wave.
- Received October 24, 2011.
- Accepted July 19, 2012.
- Copyright © 2012, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited