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Volumes and Ejection Fraction

3D Atlas - The Left Ventricle



Precise assessment of LV volume and function is pivotal for prognosis and clinical management of patients with heart disease. M-mode and 2DE have been used to assess LV volumes in clinical practice. M-mode assessment of LV volume assumes that LV may be assimilated to a prolate ellipse and its volume may be calculated by measuring its minor axis dimension and cubing it. There are many flaws in this assumption and, since it is cubed, any mistake in the minor axis measurement results in a large error in the final volume calculation. Measurement of LV volumes with 2D echocardiography relies on geometrical assumptions which are not necessarily valid in all patients and it has shown limited test-retest reliability. In addition, such assumptions make LV volume measurement inaccurate in those patients in whom they are most needed (i.e patients with previous myocardial infarction or cardiomyopathies whose LV is asymmetric or distorted).

3DE overcomes the geometric limitations of 2DE. The major advantage of 3DE resides in the possibility to quantitate LV volume without any pre-established assumption of LV geometry.

Quantitative analysis extraction of non-foreshortened, anatomically correct 4- and 2-chamber apical views (panels B and C) on the first frame of the voxel-based 3D data set obtained from apical approach, which corresponds to end-diastole . These views are used to trace the endocardial border with a semiautomated detection process. Following identification of the endocardium, the software automatically identifies the 3D endocardial surface using a deformable shell model and a cast of the cavity (panel D) is then created.
Click to enlarge the image Quantitative analysis extraction

Then the end-systole is selected by identifying the frame with the smallest LV cavity area in both apical views. providing time-volume data for the entire cardiac cycle. Surface detection is then repeated on this frame to obtain the end-systolic volume. The accuracy of the endocardial contours tracing can be checked by scrolling up and down the short-axis view with superimposed the detected endocardial border (panel A), along the left ventricular long axis and, eventually, making the necessary corrections.

The data set acquisition takes 4-5 seconds (4 consecutive cardiac cycles) and, providing no correction to the detected endocardial borders needs to be performed, the results can be obtained in 1-2 minutes.

Last generation 3DE machines are equipped with highly performant softwares which allow semi-automated or fully- automated detection of LV endocardial border, for faster and more reproducible quantitation of LV volumes.

Semi-automated detection of LV endocardium that requires the operator to select only two points at end-diastole and end-systole to obtain LV volumes (Courtesy of GE Vingmed, Horten, N).

 

Fully-automated detection of LV endocardium, allowing a fast quantitation of LV volumes (Courtesy of Siemens, MountainView, US).

Irrespective of the algorithm used to obtain the LV cast, the volumes are then measured by counting the voxels contained within the LV cast. This is the main difference between 2DE and 3DE techniques: with 2DE, volumes are calculated from simple measurements (area and diameters) using geometrical assumptions about LV shape; with 3DE, volumes are just measured. This is the main reason for the better accuracy of 3DE over 2DE in evaluating LV volumes when both are compared to cardiac magnetic resonance (CMR).

LV volumes and ejection fraction measured with 3DE have been validated against CMR1-3

Mean difference ±SD vs CMR
  3DE2DE
Jenkins 20041 EDV (ml) -4±9 -54±33
  ESV (ml) -3±18 -28±28
  EF (%) 0±7 -1±13
Caiani 20052 EDV (ml) -4±29 -23±86
  ESV (ml) -4±33 -19±60
  EF (%) -8±14 +4±16
Jacobs 20063 EDV (ml) -14±17 -23±29
  ESV (ml) -7±16 -15±24
  EF (%) -1±6 1±9

An alternative way to assess LV size and function is to reconstruct a LV cast mathematically derived from manually tracing of 3 apical planes obtained from a single R-R interval using the triplane imaging modality. The cast can be rotated on the monitor screen using the mouse or the trackball so that motion of any LV wall can be examined.

Multiplane (triplane) real-time study of the left ventricle from apical approach showing 4-chamber, 2-chamber and long-axis view (predefined angles of 60°among the different views may be changed by the operator). From manually tracing the endocardial borders in these views a mathematical model of the left ventricle is obtained. End-diastolic and end-systolic volumes and the resulting ejection fraction of the left ventricle are obtained from these data (Courtesy of GE Vingmed, Horten, N).

Multiplane (triplane) assessment of LV volumes has been reported to be accurate and time saving when compared to CMR and 2DE4 respectively.

Multiplane (triplane) modality can be used in combination with contrast agents for LV opacification, to improve accuracy of LV volume measurements, and with tissue velocity imaging to assess LV contraction synchronicity.

The use of contrast allows to image also patients with suboptimal acoustic window and to improve the accuracy of LV volume measurements5.

 

Click to enlarge the image Multiplane (triplane) images
Multiplane (triplane) images can also be acquired in tissue velocity imaging to take advantage of the simultaneous (single beat) acquisition of the three apical views of the left ventricle. By applying the tissue synchronization imaging a parametric view of LV dyssynchrony (segments with late activation in red) is displayed6.


Comparison of the two different 3DE modalities of measuring LV volumes.

 

 

Full Volume

PROS:

  • No LV foreshortening
  • No geometric assumptions about LV shape
  • Accurate when compared to CMR
  • Reproducible


CONS:

  • Multiple heart beat acquisition (AF?)
  • Off-line process
  • Frame rate 20-25 vps
  • Feasibility
  • Relatively time consuming
  • (Costs)

Triplane

PROS:

  • Fast
  • On-line
  • High frame rate
  • Single-beat acquisition (feasible in AF pts)
  • No LV foreshortening
  • Reproducible


CONS:

  • Relies on the same 2D geometric assumptions
  • Theoretically less accurate than 3D
  • (Costs)


Left ventricular volumes and ejection fraction can be quantified by using the same semi-automated algorithm on LV 3D data sets acquired from a transoesophageal appproach.

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References

  1. Jenkins C, Bricknell K, Hanekom L, Marwick TH. Reproducibility and accuracy of echocardiographic measurements of left ventricular parameters using real-time three-dimensional echocardiography. J Am Coll Cardiol 2004;44:878-86
  2. Caiani EG, Corsi C, Zamorano J, et al. Improved semiautomated quantification of left ventricular volumes and ejection fraction using 3-dimensional echocardiography with a full matrix-array transducer: comparison with magnetic resonance imaging. J Am Soc Echocardiogr 2005;18:779-88
  3. Jacobs LD, Salgo IS, Goonewardena S, et al. Rapid online quantification of left ventricular volume from real-time three-dimensional echocardiographic data. Eur Heart J 2006;27:460-68
  4. Nucifora G, Badano LP, Dall’Armellina E, Gianfagna P, Allocca G, Fioretti PM. Fast Data Acquisition and Analysis with Real Time Triplane Echocardiography for the Assessment of Left Ventricular Size and Function: A Validation Study. Echocardiography 2009;26:66-75
  5. Malm S et al JASE 2006
  6. Van de Veire et al Am J Cardiol 2007