LV Fractional Shortening Calculator

LV Fractional Shortening Explained

Fractional shortening (FS) is one of the less used measures of left ventricular systolic function. Under normal ventricular geometry, without regional wall motion abnormalities, the FS correlates strongly with ejection fraction. It is affected by pre-load and after-load and may be retrieved through M-mode measurements (parasternal long axis view PLAX) and 2D measurements.

FS is calculated by measuring the percentage change in left ventricular diameter during systole:

Fractional Shortening = (LVEDD – LVESD) / LVEDD x 100

Where:

• LVEDD = left ventricular end-diastolic diameter
• LVESD = left ventricular end-systolic diameter

Fractional shortening is a measure of how well the left ventricle is contracting itself and therefore reduces the size during systole:

• Normal FS, M-mode: >25%
• Normal FS, 2D measurement: >18%

Fractional Shortening Limitations

Whilst fractional shortening has been for several years a popular measure for quantifying ventricular function, it is not recommended anymore in the current guidelines as it is considered that volume measurements based on linear measurements may be highly inaccurate.

For example, on the M-mode, an accurate diameter measurement may not be possible if:

• The ventricle is not cut perpendicularly by the M-mode line;
• When the margins cannot clearly be delineated;
• In the case of pronounced inward motion from the lateral and septal walls in the presence of small ventricles.

It may also be impossible to clearly define end diastole and end systole, in the case of dyssynchrony or pressure or RV volume overload).

Measuring the left ventricular function from a linear image may be inexact if there are wall motion abnormalities. This can lead to an overestimation or underestimation of the LVF.

• Overestimation occurs when there is abnormal wall motion outside the segments that can be displayed with the M-mode.
• Underestimation occurs when wall motion abnormality is present in the septum or posterolateral wall.

It is important to also note that in the setting of left bundle branch block (LBBB), fractional shortening is not representative of ventricular function. This is due to the fact that the activation proceeds abnormally.

References

Oh J, Seward JB, Tajik AJ. The Echo Manual 3rd edition. Lippincott, Williams, Wilkins. 2007.

Srinivasan A, Kim J, Khalique O, Geevarghese A, Rusli M, Shah T, Di Franco A, Alakbarli J, Goldburg S, Rozenstrauch M, Devereux RB, Weinsaft JW. Echocardiographic linear fractional shortening for quantification of right ventricular systolic function-A cardiac magnetic resonance validation study. Echocardiography. 2017 ;34(3):348-358.

Park K, Chang SA, Kim HK, Park HE, Na SH, Kim YJ, Sohn DW, Oh BH, Park YB. Normal ranges and physiological changes of midwall fractional shortening in healthy korean population. Korean Circ J. 2010; 40(11):587-92.