x
_{0}

Load

cm

Related to the load that is compressing the elastic myocardium at end systole, a prerequisite for a restoring force to arise. Closely related to the velocity time integral (VTI) of the Ewave.

k

Stiffness

g/s^{2} (N/m)

LV rigidity, or the extent to which the LV resists deformation in response to an applied force. Linearly related to chamber stiffness [3] (dP/dV), and thus influences the restoring force that drives early diastolic filling. Increased in hypertension [8].

c

Viscoelasticity

g/s (N∙s/m)

Energy loss or damping of LV recoil, caused by impaired relaxation and increased viscoelasticity of the myocardium. Increased in diabetes [6] and hypertension [8].

Vmax

Ewave peak velocity

m/s

Peak velocity of blood flow across the mitral valve during early LV filling.

kx
_{0}

Peak driving force

mN

The peak force driving LV filling, analogous to the peak atrioventricular pressure gradient [14]. The product of k and x_{
0
},

cVmax

Peak resistive force

mN

The force resisting filling at peak transmitral flow. The product of c and Vmax.

1/2kx_{o}^{2}

Filling energy

mJ

Stored potential elastic energy from systole that generates rapid early LV filling. Increased in hypertension [8].

c^{2} − 4k or β

Damping index

g^{2}/s^{2} (kg∙N/m)

Reflects the balance between the factors driving and resisting left ventricular filling. Values < −900 g^{2}/s^{2} are a strong predictor of 1year mortality in elderly with heart failure [9].

KFEI

Kinematic filling efficiency index

%

An index that characterizes the efficiency of LV filling. Calculated as the ratio of the velocity time integral of the actual Ewave to the velocity time integral of a PDF modelpredicted ideal Ewave contour with no resistance to filling (c = 0) but the same stiffness (k) and load (x_{0}) as for the original Ewave. Reduced in diabetes [7].

tau

Time constant of isovolumic pressure decay

ms

Tau is used to characterize LV filling based on timeresolved high fidelity invasive measurements of LV pressure. Increased in impaired relaxation. Can be approximated by combination of PDF parameters [4].

M

Load independent index of diastolic filling

unitless

A load independent index of diastolic filling, which is decreased in patients with diastolic dysfunction and increased LV enddiastolic pressure [5]. Describes the ratio of change in peak driving force to change in peak resistive force (Δkx_{0}/ΔcVmax), calculated after acquiring Ewaves under varying loading conditions.

B

Intercept

mN

An index of diastolic filling that is increased in patients with diastolic dysfunction and increased LV enddiastolic pressure [5]. Mathematically, the yaxis intercept of the relationship between the peak driving and resistive forces from Ewaves acquired under varying loading conditions.
