Aorta – left atrium M-mode

Aorta – left atrium M-mode


Ao-LA

Mode echocardiogram at aorta-left atrium level

Mode tracing at the aorta-left atrium level is often the first M-mode tracing to be taken from the parasternal long axis view on echocardiography. The aortic valve tracing has a box like shape in open position  and is just a single line in closed position. Closure line is placed symmetrically at the centre of the aorta in usual trileaflet aortic valves. If the closure line is placed eccentrically, it would indicate a bicuspid aortic valve. The eccentricity is measured in an eccentricity index. In the premature beat there is a limited duration opening of the aortic valve and is followed by a pause. Ao: Aorta. LA: Left atrium. The ratio of aortic and left atrial diameters is usually close to 1. The ratio shifts either way when the aorta or left atrium are enlarged.

In this tracing the aortic leaflets are thin and the opening is good, indicating a good cardiac output. In the premature beat the opening is poor, suggesting a low stroke volume, which is usual for premature beats due to the lower time available for ventricular filling.
The inset image at the top middle shows the parasternal 2-D (two dimensional) image which is used to guide the position of the cursor for accurate location at the aorta-left atrium level.