Ejection Fraction Definition

Ejection Fraction Definition is the proportion of the ventricular end-diastolic volume that is expelled with each contraction, expressed as a percentage of stroke volume relative to the total volume present just before systole. Ejection fraction is one of the most widely used indices of ventricular systolic function, since it quantifies how effectively the ventricle converts its filled volume into forward output.

Mathematical Definition

Ejection fraction is calculated directly from the two boundary volumes of the ventricle.

The Ejection Fraction Equation

Ejection fraction equals stroke volume divided by end-diastolic volume, and is conventionally expressed as a percentage.

Expanded Form

Because stroke volume is itself the difference between end-diastolic and end-systolic volume, ejection fraction can also be expressed directly in terms of these two quantities.

Physiological Interpretation

Ejection fraction reflects the combined influence of the same factors that govern stroke volume.

Contractility

Greater myocardial contractility allows the ventricle to eject a larger fraction of its end-diastolic volume, raising ejection fraction.

Afterload

Increased afterload limits how completely the ventricle can empty during systole, tending to lower ejection fraction for a given level of contractility.

Independence from Absolute Volume

Because ejection fraction is a ratio rather than an absolute volume, it can remain normal even when both end-diastolic and end-systolic volumes are proportionally elevated, as in a dilated but still efficiently contracting ventricle.

Normal and Abnormal Ranges

Ejection fraction is used to categorize the systolic performance of the ventricle.

Preserved Ejection Fraction

A normal ejection fraction indicates that the ventricle is ejecting a healthy proportion of its filled volume with each beat, consistent with preserved systolic function.

Reduced Ejection Fraction

A markedly reduced ejection fraction indicates that a smaller-than-normal proportion of the end-diastolic volume is being ejected, reflecting impaired systolic function, as seen in systolic heart failure.

Diagrammatic Summary

Clinical Relevance

Ejection fraction is routinely measured through imaging modalities such as echocardiography and is central to the diagnosis, classification, and management of heart failure, distinguishing conditions with primarily reduced contractile emptying from those with primarily impaired filling despite preserved ejection fraction.