Parasternal Long Axis View

Parasternal Long Axis View

Technique

  • The ultrasound probe should be placed immediately patient left of the sternum at the level of the 3rd or 4th intercostal space 
  • To obtain a longitudinal view of the heart, the probe marker points towards the right shoulder (Figure 1) 
  • Depth should be adjusted to ensure the posterior pericardium and descending aorta are visible in the far field 
  • Gain should be adjusted so that the myocardium appears grey and blood appears black 
  • The probe should be adjusted using small movements of sliding, sweeping and rotation to optimize the view, ensuring visualization of the mitral valve, aortic outflow and the left ventricle with the septum visualized horizontally across the screen 

 

Figure 1. External landmarking for PSL image generation. 

Scanning Tips: 

  • Sometimes it is necessary to slide the probe to different intercostal spaces to find the best window to view the heart, especially mechanically ventilated patients. If struggling, try each intercostal space starting from below the clavicle 
  • If struggling to find a window, lying the patient in the left lateral decubitus position will aid in pulling the heart against the chest wall and the lung away from it 
  • An adequate view should have the ultrasound beam directed at the mid-left ventricle to mitral valve region. Both the AV and MV should be visualized as a “double barrel” and the septum should lie as flat as possible across the screen. 
  • Once a window is found, slight fanning movements should maximize the mitral valve opening and LV cavity, ideally the papillary muscles should be out of view. 
  • Finally, adjust the probe through small rotational adjustments to view the ventricle in its entire length to the apex. It should appear elongated and bullet-shaped. Foreshortening the LV cavity can lead to overestimation of wall thickening and LV function. 

 

Note: Emergency vs Cardiology convention: 

The parasternal long axis view will vary in appearance on the screen whether you are using emergency or cardiology convention. With the probe marker directed to the patient’s right shoulder the images on screen will appear as mirror images of each other depending on whether your screen marker is on the left, as in emergency convention or on the right as in cardiology convention. In the emergency convention, the apex of the heart will appear screen right and in cardiology convention, it will appear screen left (Figure 2B). 

Figure 2. Parasternal Long Axis View. Cardiology convention (A) vs Emergency Medicine convention (B)

 

What Am I Looking At?

In this view a cross section of the long axis of the heart is obtained (figure 3). In the near field just below the probe a small portion of the right ventricle is visible. Below that, the interventricular septum runs across the screen. Deep to the septum lies the left ventricular cavity. In the far field the posterior wall of the ventricle is viewed along with the posterior pericardium. Finally, a cross section of the descending aorta can be appreciated at the bottom of the screen deep to the left atrium. Also visualized in this view are the left ventricular outflow tract and aortic valve just adjacent to the interventricular septum. The mitral valve and its attachments are seen deep to the aortic valve. 

Try to follow the “Rule-of thirds.” This suggests the right ventricle, aortic root, and left atrium should each generally take up 1/3 of the screen unless one is enlarged. Interpret this cautiously if slice is off-axis  

Figure 3: Parasternal long axis cross section. Retrieved from Retrieved from Wikimedia Commons: CardioNetworks ECHOpedia

Figure 4: Parasternal Long View Cardiology Convention Labeled  

Figure 5: Parasternal Long View Emergency Medicine Convention Labeled

Clinical Utility

While pathology is out of the scope of this module, the parasternal long axis view is mainly used to assess left ventricular function. It also is a good window to view pericardial effusions when the subxiphoid view is difficult to obtain.