Glossary

ParameterDefinitionFormulaUnit
ForceAn influence that can cause an object to change its velocity.Mass × acceleration, F=m×aN
MomentumMass in motion (quantity of movement).p=m×vkg × m/s
ImpulseThe time integral of the force, i.e. the change (Δ) in momentum (p) of an object (momentum is a vector quantity, so impulse is a vector quantity).∆p=F×∆t , the impulse is defined by the AUC of the force, normalized by the time interval, thus the average value of the force, defined by 1N∑FL where the summation is taken over the period of interestN × s
HDF [2]The integral of pressure gradients over the left ventricle, normalized to left ventricular volume and blood specific weight (thus reported as % of gravity acceleration).A vector defined by the integral. HDFt=ρ∫Stx∂v∂t∙n+vv∙ndS that is taken over the LV surface boundary S(t), v(x, t) is the velocity vector field, x is the position vector, and n(x, t) is the normal unit vector%
HDP [3]A physics-based measure that takes into account the dynamics of the space-time shape changes in combination with blood flow.d(HW)/dt. A scalar quantity defined by the scalar product between the HDF vector, normalized by the LV volume V(t), and another vector obtained by a surface integral HDPt=HDF(t)V(t)∙∫S(t)xv∙ndSW = J/s
HWThe displacement of an object due to force.Force × distance. The time integral of the HDP, computed by TN∑HDP where it contains the time interval T, to transform the power into workJ = N × m
RMSThe square root of the arithmetic mean of the squares of a set of values. Based on the mathematical formula, this parameter cannot differentiate between positive and negative curves.Computed by 1N∑HDFL2 where the summation is taken over the period of interest (whole cardiac cycle, systole, diastole)-
AUCThe space between a curve and a straight line that connects two points on that curve.A = ∫abf(x)dxN × s

AUC: area under the curve; HDF: hemodynamic forces; HDP: hemodynamic power; HW: hemodynamic work; J: Joule; N: Newton; RMS: root mean square; W: Watt