Background Normal coronary blood flow is principally determined by a backward-travelling decompression (suction) wave in diastole. This wave may be attenuated in chronic heart failure, reducing blood flow, as regional relaxation and contraction overlap in timing. We hypothesised that biventricular pacing by restoring left ventricular (LV) synchronisation and improving LV relaxation might increase this decompression wave, improving coronary flow.
Method and Results Ten CHF patients (9 males; age 65±12; EF 26±7%) with left bundle branch block (LBBB, QRS duration 174±18 ms) were atrio-biventricularly 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 (BiV-40), 120 ms (BiV-120), and separately pre-identified haemodynamically-optimal AV delay (BiV-Opt). Compared against LBBB, BiV-Opt enhanced coronary flow by 15±4% (p=0.003), LV dP/dtmax by 19±4% (p<0.001) and negdP/dtmax by 16±3% (p<0.001). The cumulative intensity of the diastolic backward decompression (suction) wave increased by 36±8% (p=0.011). The majority of the increase in coronary flow occurred in diastole (64±8%, p=0.03). The systolic compression waves also increased, forward by 33±11% (p=0.043) and backward by 33±10% (p=0.014). BiV-120 generated a smaller LV dP/dtmax (by 23±12%, p=0.034) and negdP/dtmax (by 23±10%, p=0.039) increase than BiV-OPT, against LBBB as reference; BiV-Opt and BiV-120 were not statistically different in coronary flow or waves. BiV-40 was no different from LBBB.
- Biventricular pacing
- coronary flow
- wave intensity