TYK78
Concerning pediatric echocardiography, what is true concerning shortening fraction (SF) versus ejection fraction (EF)?
A. Ejection fraction can be measured with M-mode echocardiography
B. Ejection fraction is normally 0.28-0.44 in pediatric patients
C. Shortening fraction uses ventricular diameters only
D. Shortening fraction is normally 50-70%
Answer
The answer is C.
Ejection fraction is the most commonly used ECHO parameter to measure contractility. EF has several limitations including being a load dependent measurement. The EF is practically measured by the following calculation:
- EF = ((End diastolic volume-End systolic volume)/(End diastolic volume))
A normal EF is usually greater than 50-60%.
Shortening fraction (SF) is a two dimensional equivalent of EF. When only the end diastolic (or systolic) DIAMETER is known (remember EF uses a VOLUME measurement), then shortening fraction must be used. The normal shortening fraction is usually >0.28. SF was originally used when ECHO consisted only of M-mode (one dimension). More recent advances in 2-D echocardiography have improved the accuracy of generating a 3-D value (volume and subsequent EF) from a 2-D image. However, despite these differences, there are some cardiologists and institutions who still report contractility in SF. You just need to know the normals for each and which one they are talking about. Remember, SF does not equal EF.
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