What is the normal result for left ventricular ejection fraction (LVEF)?
Is normal ejection fraction 50-70, or 55-70? I’ve seen a lot of articles that disagree on what is a normal EF. While anything >55 is normal and anything <50 is abnormal, what about that grey area of 50-54% EF? And is EF very complex to measure?
Submitted by Rich from Pennsylvania on 03/22/2015
Taking the question from the end, measurement of LVEF can be accomplished by a number of different means. Today, this is usually done with one of a host of imaging techniques such as echocardiography, magnetic resonance imaging, scintigraphy (nuclear medicine), or contrast ventriculography. While the imaging tests, from a patient perspective, may seem relatively simple, the machines themselves and the (often computer-aided) algorithms used in these modalities are moderately to highly complex. Each of the modalities has its own advantages and disadvantages, and each has a certain range of accuracy. For an ejection fraction in the range of 50% to 55%, most of the commonly used tests, if carefully performed, are accurate within a few percentage points (e.g. 55% plus or minus 3%).
With respect to the lower limit of “normal” LVEF, it is important to remember that even at rest, the LV pumps a slightly different amount of blood in every beat. Things like time of day (biological cycles), eating (what and when), position (supine vs. upright), breathing, medications, etc. can all slightly change LVEF in a normal person. All of these factors make it practically impossible to define a single limit that applies to all persons. A value that may be normal for one individual in a certain setting may be slightly low for that same person in a different physiological setting or for a different person under similar circumstances.
In summary, given the intrinsic slight inaccuracies of the methods for measuring LVEF and the routine physiological variations in LVEF, the lower limit of normal for LVEF can only be defined in terms of general averages for a population of people. As suggested in the question, this number is going to be in the range of 50-55%. Even accepting this general range, there will be a few people with no recognizable heart problem who have an LVEF in the high 40s and many more with clear-cut heart problems who have an LVEF in the high 50s or even the 60s. Thus, as with many other physiological variables, the human population demonstrates a range of “normal” values distributed in what is often referred to as a “bell-shaped curve.” For all of these reasons, many scientists now prefer to use the term “reference value” rather than “normal value,” to emphasize the normality of individual variations.
P.S. As confusing as defining the lower limit of “normal” may be, defining the upper limit is much more difficult, for both technical and physiological reasons.