First-in-man evidence of the mechanistic effects of biventricular pacing on coronary physiology

Abstract

BackgroundNormal coronary blood flow is principally determined by a diastolic backward travelling decompression (suction) wave. Dyssynchronous heart failure may attenuate suction. We hypothesised that biventricular pacing, by restoring left ventricular (LV) synchronisation and improving LV relaxation, might increase this suction wave and coronary flow. MethodsTen patients with congestive heart failure (nine men; mean age 65 years [SD 12]; mean ejection fraction 26% [SD 7] with left bundle branch block (LBBB, mean QRS duration 174 ms [SD 18]) underwent atriobiventricular pacing at 100 beats per min. 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). Data are given as median (IQR). FindingsCompared with LBBB, BiV-Opt enhanced coronary flow velocity time integral (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). Much 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 did BiV-OPT, with 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. InterpretationWhen biventricular pacing improves left ventricular contraction and relaxation, it increases coronary blood flow velocity, predominantly by increasing the dominant diastolic backward decompression wave. FundingBritish Heart Foundation.