= Right ventricular ejection fraction
{title2=$\mathrm{RVEF}$}
\b[Right ventricular ejection fraction] is the fraction of the <right ventricle>'s <end-diastolic volume> that leaves its cavity during <systole>. If $V_{\rm ED}$ is the filled volume and $V_{\rm ES}$ the residual <end-systolic volume>,
$$
\mathrm{RVEF}=\frac{V_{\rm ED}-V_{\rm ES}}{V_{\rm ED}}
=\frac{\mathrm{SV}}{V_{\rm ED}},
$$
where $\mathrm{SV}$ is <stroke volume>. It is a dimensionless <ratio>, usually reported as a <percentage>. The filling and ejection phases must refer to the same <cardiac cycle>; the <tricuspid valve> and <pulmonary valve> determine the normal direction of <blood flow>.<Anatomy and Physiology 2e by J. Gordon Betts and others>[§19.1, Right Ventricle and Heart Valves]{ref}
For example, $V_{\rm ED}=120$ mL and $V_{\rm ES}=60$ mL give $\mathrm{SV}=60$ mL and $\mathrm{RVEF}=50\%$. A second <right ventricle> with volumes 200 and 100 mL also has $50\%$ <right ventricular ejection fraction>, but its <stroke volume> is 100 mL. A fraction describes emptying relative to the initial volume; it does not specify an absolute <cardiac output>.
A practical volumetric approach uses <magnetic resonance imaging> at multiple phases and <image segmentation> to estimate the two cavity volumes.<Reference right ventricular systolic and diastolic function normalized to age, gender and body surface area from steady-state free precession cardiovascular magnetic resonance by Alicia M. Maceira and others>[Abstract: Aims; Methods and results]{ref} Consistent boundary choices matter because two measurements enter one <ratio>. For small volume errors, direct differentiation gives
$$
\delta\mathrm{RVEF}\simeq
\frac{V_{\rm ES}}{V_{\rm ED}^2}\,\delta V_{\rm ED}
-\frac{1}{V_{\rm ED}}\,\delta V_{\rm ES}.
$$
Shared boundary errors need not act like independent errors. Moreover, cavity volume loss includes any backward flow through an incompetent <tricuspid valve>; the formula alone does not prove that all of the calculated <stroke volume> reached the <pulmonary trunk>.
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