Initial displacement, effectively equivalent to the E-wave VTI
c
Viscoelastic loss index
N·s·m−1
g/s
Friction-like force which opposes the ventricle returning to its resting state after systole
k
Chamber stiffness
N·m−1
g/s2
Analogous to the spring stiffness constant, and correlated with invasive LV dP/dV
kx0
Maximum driving force
N
dynes or mN
The initial peak driving force of diastole. Proportional to the peak atrioventricular pressure gradient
1/2kxo2
Potential energy
J
ergs or mJ
Stored potential elastic energy to generate rapid recoil during early filling
cEpeak
Peak resistive force
N
mN
The initial peak resistive force of diastole. Resistive (viscoelastic) force at peak flow
M
Load independent index of diastolic filling
N/N
unitless
Unitless ratio of maximum driving force to peak resistive force (kx0/cEpeak)
c2-4k
Damping index β
g2/s2
Relative contribution between damping (c) and recoil (k). Negative values reflect underdamped filling, positive values reflect overdamped filling
KFEI
Kinematic filling efficiency index
cm/cm
unitless
Ratio of the VTI of the acquired E-wave contour fit via PDF to the VTI of the PDF model-predicted ideal E-wave contour with no resistance to filling (c = 0)
Slope intercept B
Maximum driving force for cEpeak = 0
N
mN
y-intercept of the equation: kxo = M·cEpeak + B; peak driving force in the setting of no resistance, related to LVEDP
