Parasternal Short Axis

Surface Anatomy

For the parasternal short axis view the transducer is applied to a similar position on the precordium as used for the long axis view. However, the transducer marker points to the patient’s left shoulder. This corresponds to approximately 90 degrees of rotation. Four imaging planes are described for the parasternal short axis. These are the basal, mitral, mid papillary and apical plane. Movement across several intercostal spaces may be necessary. This is usually up or down one space. This window is best obtained with the patient in the left lateral decubitus position.

3d

Parasternal Short Axis Transition

As a general rule of thumb the parasternal short axis (PSAX) mitral view is captured with the transducer perpendicular to the chest wall. Sweeping the transducer medially and superiorly will capture the basal view. Conversely, sweeping the transducer laterally and inferiorly will capture the mid-papillary and apical views.

Basal

parasternal short axis basal

As a starting point the aortic valve annulus should be visible. This is the so-called Mercedes benz sign, though it is upside down. This view is also known as the right ventricular inflow/ outflow view as the right side can be seen to wrap around the aortic annulus.

parasternal short axis basal

Starting on the lower left side of the screen, the right atrium is visible leading to the tricuspid valve and then the right ventricle at the top of the screen (most anteriorly). Right ventricular free wall diastolic collapse may be assessed if tamponade is suspected. Blood flow here is parallel to the ultrasound beam and accurate measurement of flow velocities can be made. From the right ventricle, blood flows out into the pulmonary artery through the pulmonary valve. The interatrial septum is visible between the right and left atria. This allows for assessment of septal defects.

parasternal short axis basal

The aortic valve is seen at the centre of the image. All three leaflets should be visible. The structure of the valve may be assessed noting that posterior portions of the valve may not be visible in situations where there is heavy calcification. Function however cannot be reliable assessed as blood flow is perpendicular to the ultrasound beam. Despite this cloud doppler is sometimes placed across the valve to asses for severe regurgitant jets. Structure and function of the tricuspid valve may be assessed here. This is also a view from which tricuspid regurgitation is assessed,. The velocity of the regurgitant jet is used in the estimation of pulmonary artery systolic pressures. Pulmonary valve structure and function may also be assessed here.

Mitral

parasternal short axis mitral

This view is accomplished by inferior and lateral angulation of the ultrasound probe from the basal imaging plane.

parasternal short axis mitral

The relationship of the left and right ventricle are visible here allowing comparison of size and function.

parasternal short axis mitral

Six of the seventeen left ventricular segments are visible here. This view is of particular utility in the assessment of regional wall motion abnormalities.

parasternal short axis mitral

Both leaflets of the mitral valve are visible here, with the appearance of a fish’s mouth. The leaflets should be thin and mobile, the anterior leaflet appearing particularly large and mobile. Colour doppler across the valve is sometimes done to assess for mitral regurgitation.

Mid Papillary

parasternal short axis mid papillary

This view is accomplished by further inferior and lateral angulation of the ultrasound probe from the mitral imaging plane.

parasternal short axis mid papillary

The relationship of the left and right ventricle are visible here allowing comparison of size and function.

parasternal short axis mid papillary

Six of the seventeen left ventricular segments are visible here. This view is of particular utility in the assessment of regional wall motion abnormalities.

parasternal short axis mid papillary

Both the anterolateral and posterior medial papillary muscles are visible here. The pericardium is visible anteriorly and posteriorly.

Apical

parasternal short axis apical

Lastly the apical portion of the left ventricle is achieved by further inferior and lateral angulation of the ultrasound probe from the mid papillary plane.

parasternal short axis apical

Note that the right ventricle is not visible here.

parasternal short axis apical

This portion of the left ventricle is divided into 4 segments.