Background
Parameter | Name | Unit (SI unit) | Physiological description |
---|---|---|---|
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 E-wave. |
k
| Stiffness | g/s2 (N/m) | |
c
| Viscoelasticity | g/s (N∙s/m) | |
Vmax | E-wave 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. |
1/2kxo2 | Filling energy | mJ | Stored potential elastic energy from systole that generates rapid early LV filling. Increased in hypertension [8]. |
c2 − 4k or β | Damping index | g2/s2 (kg∙N/m) | Reflects the balance between the factors driving and resisting left ventricular filling. Values < −900 g2/s2 are a strong predictor of 1-year 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 E-wave to the velocity time integral of a PDF model-predicted ideal E-wave contour with no resistance to filling (c = 0) but the same stiffness (k) and load (x0) as for the original E-wave. Reduced in diabetes [7]. |
tau | Time constant of isovolumic pressure decay | ms | Tau is used to characterize LV filling based on time-resolved 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 end-diastolic pressure [5]. Describes the ratio of change in peak driving force to change in peak resistive force (Δkx0/ΔcVmax), calculated after acquiring E-waves under varying loading conditions. |
B | Intercept | mN | An index of diastolic filling that is increased in patients with diastolic dysfunction and increased LV end-diastolic pressure [5]. Mathematically, the y-axis intercept of the relationship between the peak driving and resistive forces from E-waves acquired under varying loading conditions. |
Implementation
Echocardiographic image acquisition
Loading and visualization of Doppler data from DICOM images
Detection of the velocity profile
Curve fitting and adjustment of the fitting algorithm input
Automatic detection and curve fitting
Quality control
Alternative method to curve fitting
Export of data
Statistical analysis
Results
Median | Range | Interquartile range | |
---|---|---|---|
c (g/s2) | 17.4 | 10.6–32.8 | 15.5–20.4 |
k (g/s) | 177.4 | 106.5–294.8 | 153.9–206.9 |
x0 (cm) | 11.7 | 7.7–17.9 | 10.3–12.8 |
Vmax (m/s) | 0.7 | 0.5–1.3 | 0.6–0.8 |
Edec (ms) | 236 | 139–473 | 205–273 |
VTI (cm) | 12.4 | 8.1–19.1 | 11.0–13.5 |
Tau (ms) | 70.1 | 47.6–151.6 | 62.0–83.3 |
KFEI (%) | 53.0 | 46.1–64.1 | 51.4–54.8 |
c2 − 4k (g2/s2) | −382 | −224– − 826 | −295– − 474 |
Filling energy (mJ) | 1.1 | 0.6–3.3 | 0.9–1.4 |
Peak driving force (mN) | 19.6 | 12.4–40.6 | 17.6–22.7 |
Peak resistive force (mN) | 12.5 | 7.6–27.3 | 10.6–14.7 |
M (dimensionless) | 1.17 | 0.96–1.49 | 1.06–1.26 |
B (mN) | 5.3 | 1.6–9.7 | 4.1–6.7 |
Inter-and intraobserver repeatability
3A | Intraobserver | Interobserver | ||||||
CV (%) | Difference (%) | SD | ICC | CV (%) | Difference (%) | SD | ICC | |
c
| 13.2 | 12.6 | 9.8 | 0.80 | 11.6 | 9.8 | 6.1 | 0.92 |
k
| 9.3 | 9.1 | 7.3 | 0.93 | 14.0 | 9.0 | 8.3 | 0.88 |
x
0
| 6.6 | 4.7 | 4.8 | 0.95 | 5.9 | 4.7 | 4.6 | 0.96 |
Vmax | 5.1 | 3.3 | 4.0 | 0.98 | 4.0 | 3.0 | 2.6 | 0.99 |
Edec | 11.1 | 7.6 | 7.5 | 0.92 | 11.8 | 9.1 | 6.2 | 0.93 |
VTI | 6.0 | 4.1 | 4.2 | 0.96 | 5.3 | 4.3 | 3.4 | 0.97 |
Tau | 11.7 | 8.9 | 8.4 | 0.88 | 13.3 | 10.2 | 6.7 | 0.91 |
KFEI | 2.7 | 2.6 | 2.0 | 0.89 | 2.5 | 2.2 | 1.9 | 0.91 |
c
2
− 4k | 18.7 | 18.9 | 30.1 | 0.92 | 14.3 | 16.2 | 14.7 | 0.95 |
Energy | 14.6 | 13.7 | 9.6 | 0.94 | 10.6 | 9.8 | 6.4 | 0.98 |
Peak driving force | 10.7 | 9.8 | 8.1 | 0.92 | 10.6 | 8.1 | 6.0 | 0.95 |
Peak resistive force | 14.6 | 13.5 | 10.6 | 0.85 | 12.9 | 10.6 | 7.2 | 0.93 |
M | 15.3 | 12.1 | 8.3 | 0.51 | 23.7 | 17.7 | 20.8 | 0.16 |
B | 44.7 | 39.5 | 32.6 | 0.37 | 51.1 | 37.0 | 38.7 | 0.32 |
3B | Intraobserver | Interobserver | ||||||
CV (%) | Difference (%) | SD | ICC | CV (%) | Difference (%) | SD | ICC | |
c
| 13.6 | 12.5 | 10.6 | 0.80 | 11.6 | 10.4 | 5.3 | 0.93 |
k
| 9.0 | 8.6 | 6.8 | 0.94 | 13.7 | 9.2 | 7.7 | 0.88 |
x
0
| 5.5 | 3.9 | 4.8 | 0.96 | 5.5 | 4.3 | 4.5 | 0.96 |
Vmax | 2.4 | 2.3 | 1.9 | 0.99 | 3.8 | 3.0 | 2.5 | 0.99 |
Edec | 9.7 | 6.9 | 7.1 | 0.94 | 11.5 | 7.9 | 6.6 | 0.94 |
VTI | 4.0 | 2.9 | 3.1 | 0.98 | 5.1 | 4.2 | 3.2 | 0.97 |
Tau | 10.7 | 8.6 | 8.0 | 0.90 | 13.1 | 8.8 | 7.1 | 0.92 |
KFEI | 2.9 | 2.6 | 2.3 | 0.88 | 2.6 | 2.4 | 1.8 | 0.91 |
c2 − 4 k | 17.9 | 15.8 | 25.0 | 0.93 | 12.7 | 13.1 | 11.9 | 0.96 |
Energy | 16.0 | 14.2 | 11.0 | 0.93 | 10.9 | 9.7 | 6.5 | 0.98 |
Peak driving force | 11.0 | 10.5 | 8.5 | 0.91 | 10.8 | 8.2 | 5.9 | 0.94 |
Peak resistive force | 15.7 | 14.5 | 11.8 | 0.83 | 13.3 | 10.9 | 6.9 | 0.93 |
M | 15.4 | 12.1 | 8.3 | 0.61 | 13.5 | 10.2 | 11.2 | 0.71 |
B | 44.7 | 39.5 | 32.6 | 0.51 | 27.9 | 19.6 | 19.9 | 0.83 |