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Table 1 Explanation of PDF paramaters and indices

From: Mechanistic validation of the 2016 American Society of Echocardiography/European Association of Cardiovascular Imaging Guidelines for the assessment of diastolic dysfunction in heart failure with reduced ejection fraction

PDF Parameter or Index Physiologic Analog SI Units Expressed as Description
x0 Effective volumetric load cm cm 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
  1. VTI velocity time integral, LVEDP left ventricular end-diastolic pressure