Transducer Position & Left Ventricular Geometry
Learn to position the transducer correctly to avoid long axis foreshortening
April 14th, 2022
Pages 1-8
Topics:
- Ultrasound transducer
- Left ventricular long axis
- Foreshortening
- Left ventricular geometry
- Left ventricular volumes and ejection fraction
- Apical views
Qualitative evaluation of EF.
The qualitative “eyeball” method” of quantifying LV ejection fraction (EF) is widely used, especially in the USA, supported by the Literature. A 1997 English study found that the “eyeball” estimate of LV function was of prognostic significance (relative risk of poor vs. good, 2.248, p<.001). No other quantitative echo index was of independent prognostic significance when all variables were tested in a regression model.
Reference: Prognostic implications of qualitative assessment of LV function compared to simple routine quantitative echocardiography (Silcocks et al. Heart 1997;78:237, Sheffield, UK)
The qualitative “eyeball” method relies more heavily than the quantitative Simpson method to calculated EF on the quality of the acquired imaging, and I am referring here to the achievement of a correct LV geometry. This is because when using the Simpson method we have immediate evidence of the LV long axis and volume in each view (4-chamber and 2-chamber).
Figure 1. tt2043.
Let’s now consider this 4-chamber view obtained in a patient during a postoperative outpatient follow-up for an aortic valve mechanical prosthesis. This is a real case scenario.
The calculated (Simpson method) end-diastolic volume was 234 ml and the EF= 66.2 %, with normal function of the valve prosthesis.
What do you think of the quality of the imaging and of the LV geometry: is it correct ? Would you rely on these numbers ?
Well: no. The geometry is clearly not correct, and consequently the numbers are unreliable. Let’s see how we can simply and quickly reach this conclusion.