M-mode echocardiogram of normal aorta and left atrium

The M-mode echocardiogram is obtained from the long axis parasternal two dimensional view (panel A); the dotted line represents the M-mode beam passing through the aortic root, the right (R) and noncoronary (N) cusps of the aortic valve, and the left atrium (LA). The atrium is measured at end systole (arrows) when the descent of the left ventricle base has resulted in maximal filling.