Left atrium dimensions

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Contents

 LA function

The left atrium has three major roles:

-contractile pump that delivers 15% to 30% of the LV filling

-reservoir that collects pulmonary venous return during ventricular systole

-conduit for the passage of stored blood from the LA to the LV during early ventricular diastole.



LA dimensions

LA size is important and has been related to adverse cardiovascular outcomes. LA dilatation reflects long-term increased filling pressure: diastolic dysfunction and/or mitral valve disease, stenosis or regurgitation.

LA size is measured at the end-systole, when the LA chamber is at its greatest dimension

 

LA antero-posterior diameter in parasternal long axis view 

This method of measurement has been done extensively in clinical trials, but is no longer recommended.

LA diameter is measured in parasternal long axis, perpendicularly to the LA walls. You will measure the LA diameter in end-systole, from leading edge of the posterior aortic wall to the leading edge of the posterior LA wall.

It can be measured in 2D, or in Mmode if the ultrasound beam is perpendicular to the LA walls.

 
Measurement LA PSL 2D.jpg

  

LA minor and major axis in apical 4 chamber view

You have to get a good apical 4 chamber view, with complete visualization of the atria, mitral and tricuspid valve, and both ventricles.

This method is not recommended, measurement of LA area and volumes are preferred.


 
Measurement LA major minor axis A4C.jpg


LA area and volume in apical 4 chamber view

LA area and volume are the most reliable measurements for the determination of LA enlargement.

The measurement should be done at end-systole, on the frame just before the opening of the mitral valve. You need to get a good apical 4 chamber view. You will trace the inner border of the LA, excluding the area under the mitral valve annulus and the inlet of the pulmonary veins. The LA shape should be roughly square.

LA volume may be measured using Simpson’s rule, similar to its application for LV measurements, which states that the volume of a geometric figure can be calculated from the sum of the volumes of smaller figures of similar shape.

 

Measurement LA area A4C.jpg

Normal values

 

LA dimensions Normal Mildly dilated Moderately dilated Severely dilated
Diameter (mm) 28-40 41-46 47-52 >52
Major axis (mm) 41-61 62-67 68-76 >77
Area (cm2) <20 20-30 30-40 >40
Volume (ml) 22-58 59-68 69-78 >79

  

References

Lang RM, Bierig M, Devereux RB. Recommendations for chamber quantification. J Am Soc Echocardiogr. 2005 Dec;18(12):1440-63

Vasan R.S et al. Distribution and categorization of echocardiographic measurements in relation to reference limitsthe Framingham heart study; formulation of a height- and sex-specific classification and its prospective validation.   Circulation (1997) 96 : pp 1863-1873

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