Ventricular-arterial interaction: cardiac effects of mean versus pulsatile arterial load

The influence of the two principal components of vascular loading, mean resistance and pulsatile load, on the contractile and energetic performance of the left ventricle are discussed. The data suggest that while large changes in mean resistance leading to varying ejection fraction can influence both cardiac systolic mechanics and energetic efficiency, substantial changes in pulsatile loading do not. They provide an explanation for why pulsatile loading does not necessarily result in a coronary supply/demand imbalance. By not significantly altering chamber systolic performance of elastance (i.e. stiffness), the pulsatile load results in parallel increases in coronary systolic pressure and flow, allowing adequate perfusion despite the reduced mean diastolic perfusion pressure. Future studies are required to better determine how cardiac disease alters the interplay between vascular load and cardiac performance.