M-Mode cuts are usually obtained from two dimensional (2-D) views after the proper positioning of the transducer to get a good image. Aorta – Left atrium cut for measuring the aortic and left atrial diameters on M-Mode are usually guided by the parasternal long axis 2-D image (seen above the M-Mode image as an inset). The aortic dimension is measured in diastole while left atrial dimension is measured in end systole. The open position of the aortic valve can be seen as a horizontal box (pointed by yellow line), while the closed position is seen as a single line (pointed by the green line). Usually aortic and left atrial dimensions are similar in magnitude in this view.
Ao: Aorta; LA: Left atrium; RVOT: Right ventricular outflow tract.
Aortic valve closure line is seen at the centre of the aorta normally. Eccentric closure line is suggestive of a bicuspid aortic valve with asymmetric leaflets. Thin lines of the aortic valve in open position shows that the aortic leaflets are not thickened. When they are thickened, dense echoes or sometimes multiple echoes lines are seen. The open position of the aortic valve gives an indication of the cardiac output. When the cardiac output is low as in severe heart failure, the opening excursions are lesser. It also gives an indication of the aortic orifice in case of aortic stenosis. The movement of the aortic wall is also an indication of the cardiac output.