End-diastolic volume ($V_{\mathrm{ED}}$)

End-diastolic volume is the volume of blood in a specified ventricle at the end of filling, before the subsequent ejection. It is the starting volume in the usual volumetric stroke volume calculation and the denominator of ejection fraction:The right ventricle and left ventricle each have their own end-diastolic volume. The chamber, phase and measurement convention must be identified before two values are compared.

For a constructed example, a chamber filling to 120 mL and ending ejection at 50 mL has a stroke volume of 70 mL and ejection fraction about $58.3\%$. Another chamber filling to 180 mL and ending at 110 mL has the same 70 mL stroke volume, but ejection fraction about $38.9\%$. Equal ejected volumes do not imply equal relative emptying.

The quantity can be obtained from time-resolved images by choosing the filling phase and identifying the complete cavity. A primary right-ventricular magnetic resonance imaging study generated volumes from cine images with three-dimensional modelling; its reference analysis also considered age, sex and body size.^[ref] These factors help explain why an isolated volume should not be treated as a universal reference value.

For a simple sum-of-slices model, $V_{\mathrm{ED}}\simeq {\sum }_i{A}_i\Delta z_i$, where $A_i$ is the measured cavity area in a slice and $\Delta z_i$ its represented thickness. Omitting a slice with area 10 cm${}^2$ and represented thickness 0.8 cm omits about 8 mL. This example connects image segmentation and coverage to a concrete volume error; it does not require a spherical ventricle.