Volumetric measurements are based upon the principle that LV
volumes can be calculated from 2D
measurements of the LV
as long as certain assumptions about the shape of the LV
apply. The more distorted the LV
(e.g. as a result of an aneurysm), the less reliable such volumetric measurements become.
Modified Simpson’s rule method
Modified Simpson’s rule method is the best (and most commonly used) way of calculating LV
volumes. It is also known as the biplane method of discs, as it works on the principle that the LV
cavity can be considered as a stack of elliptical discs of
differing sizes from base to apex. If the volume of each disc is known (from its area and thickness), then the overall LV
volume is equal to the volume of all the discs added together.
Measurement of left ventricular (LV
) volume using the modified Simpson’s rule method (EDV
= end-diastolic volume)
Echo machines automate much of the process and require the operator simply to measure the length of the LV
(long axis) and to trace the outline of the LV
endocardium in one (or preferably two) planes. To do this:
In the apical 4-chamber view obtain the best view you can of the LV
, paying particular attention to endocardial border definition and avoidance of foreshortening. The use of an echo contrast agent (Chapter 9) may help delineate the endocardium if the image quality is suboptimal.
Freeze a loop and find the end-diastolic image. Now trace the endocardial border from the mitral valve annulus all the way down to the apex and then back up to the annulus on the opposite side. Ignore any papillary muscle that may be visible. The machine will normally join up the start and finish points with a straight line across the mitral valve, to enclose the entire LV
cavity within the traced area. The machine will then automatically split the traced area into a stack of discs (usually 20).
Measure the length of the LV
long axis from the apex to the mid-point of the mitral valve. The machine will now use these measurements to calculate LV
enddiastolic volume (LVEDV
, Fig. 15.4
Scroll to the end-systolic frame and repeat steps 2 and 3 to obtain the LV
endsystolic volume (LVESV
Although a measurement taken in just one plane will give you a value for LVEDV
, this does make the assumption that each of the discs is circular. Repeating the measurements in the apical 2-chamber view takes better account of the elliptical cross-section of the LV
and any regional wall motion abnormalities.
The area-length method can be useful for estimating LV
volumes when the endocardium cannot be seen clearly enough to allow accurate tracing. However, it does make major assumptions (and simplifications) about the shape of the LV
In the parasternal short axis view, mid-LV (papillary muscle) level, freeze a loop and find the end-diastolic frame. Perform planimetry by tracing the endocardial border to calculate the cross-sectional area of the LV
cavity at this level in cm2
. Ignore the presence of the papillary muscles as you trace the endocardium.
In the apical 4-chamber view, in the end-diastolic frame, measure the length of the LV
long axis from the apex to the mid-point of the mitral valve in cm.
, in mL, is given by:
Scroll to the end-systolic frame and repeat steps 1 to 3 to obtain the LVESV
and LVESD can be adjusted for BSA
volume index’). Table 15.2
shows the reference ranges for males and females.
Table 15.2 Left ventricle volumes – reference ranges