What does the term "ejection fraction" refer to in echocardiography?

Ejection fraction is a critical measurement in echocardiography that specifically refers to the percentage of blood that is ejected from the left ventricle during each heartbeat. It is calculated by dividing the stroke volume (the volume of blood pumped out with each beat) by the end-diastolic volume (the total volume of blood in the ventricle just before contraction) and then multiplying by 100 to get a percentage.

This measurement provides important information about the heart's efficiency and function, particularly in assessing conditions such as heart failure. A normal ejection fraction typically ranges from 55% to 70%. Values below this range may indicate reduced heart function or damage, while values above this range could suggest hypertrophic conditions or other alterations in cardiac physiology.

The other choices refer to different anatomical or functional aspects of the heart. For instance, heart muscle mass pertains to the size of the ventricular myocardium, total blood volume in the heart refers to the total capacity rather than the functional output, and the rate of blood flow describes the speed at which blood circulates rather than the efficiency of contraction. Ejection fraction distinctly captures the contractile performance of the heart, making it a valuable clinical marker.