LV Systolic Function 1
This station covers LV Dimensions (LV Chamber Quantification) and Fractional Shortening (FS%). These are obtained in the PLAX view.
A. LV Chamber Dimensions
- LV Dimensions are measured in the parasternal long axis view (PLAX).
- 2D measurements are preferred over M-MODE, as the latter may result in errors if the measurements are unknowingly made obliquely. (See image below)
- The LV chamber is measured in end-diastole and end-systole. (LVIDd & LVIDs)
- LVIDd = Left Ventricular Internal Diameter in Diastole
- LVIDs = Left Ventricular Internal Diameter in Systole
- SWT = Septal Wall Thickness
- PWT = Posterior Wall Thickness
B. Fractional Shortening (FS%)
- Fractional Shortening can be used to quantify LV systolic function
- Image shows an example calculation of FS%
- FS > 27% is consistent with normal LVEF
- FS < 15% indicates severely reduced LVEF
- Limitations include the presence of RWMAs, LBBB / Dyssynchrony, Regional wall motion abnormalities, Poor image quality, Abnormal septal motion, Inadequate M-Mode orientation
C. Clinical Examples
Clip 1
A 70 year old patient becomes hypotensive after induction of anaesthesia. His BP is 65/34 despite multiple 100mcg boluses of phenylepherine and 9mg of ephedrine. You perform a FoCUS study. The PLAX view and M-Mode fractional shortening are shown. What is the patient's LV systolic function?
Thhe 2D PLAX clip on the left shows that the LV contracts well. Visually, ejection fraction appears normal. This is confirmed with a fractional shortening of 40.4%. FS% > 25-27% indicate normal LV systolic function.
The Teicholz calculation is used to convert the linear LV dimensions into volumes. The end diastolic and end systolic volumes are shown, as obtained by the Teicholz method (Teich). This method is prone to error as it relies on many geometric assumptions. It should not be relied on.
A better way to obtain a rough estimate of ejection fraction from fractional shortening is to multiply FS% by 2.
The Teicholz calculation is used to convert the linear LV dimensions into volumes. The end diastolic and end systolic volumes are shown, as obtained by the Teicholz method (Teich). This method is prone to error as it relies on many geometric assumptions. It should not be relied on.
A better way to obtain a rough estimate of ejection fraction from fractional shortening is to multiply FS% by 2.
Clip 2
A 65 year old man has been on the ICU, on inotropic support & mechanical ventilation for the past 3 days. He was diagnosed with severe sepsis secondary to community acquired pneumonia. He is currently supported on adrenaline and noradrenaline. A bedside FoCUS scan is performed to determine his LV systolic function.
The LV looks dilated on the apical 4 chamber view on the left. M-Mode is used to determine fractional shortening. The PSAX view is used. Fractional shortening is 15.4%. This is consistent with severe LV systolic failure. The EF calculated by the Teicholz calculation is 31.4%.
