Learning Ultrasound – 5 – Scanning Technique For The Parasternal Long Axis Cardiac View

All of the posts of the series Learning Ultrasound are excerpts from the book Point-Of-Care Ultrasound for Emergency Physicians — “The EDE Book”. I purchased the e book two years ago. The e book is only available on Apple devices. The e book is only about $15 and it is simply the best there is on learning  to perform point of care ultrasound (POCUS). You need to buy it now.

There are two skills that need to be developed to become a successful point-of-care ultrasonographer:

  1. The ability to obtain adequate (meaning interpretable) scans. And this is, by far, the most difficult part of learning POCUS. And it is at teaching this critical skill that the book, Point-Of-Care Ultrasound for Emergency Physicians — “The EDE Book”, excels. There is no better ultrasound book for teaching the difficult skill of image acquisiton. The first part of this post is concerned with learning image acquisition.
  2. The ability to interpret ultrasound scans. [This link jumps to the part of this post where cardiac ultrasound interpretation is reviewed if you are already skilled at image acquisition.]

I have posted these Learning Ultrasound series, temporarily, for a friend who does not currently have access to an Apple device.

First we’ll watch two excellent YouTube videos on what you will see in a well performed parasternal long axis cardiac scan from Sonosite.

Then we will go over the often difficult technical points of conducting the exam with help from Point-Of-Care Ultrasound for Emergency Physicians — “The EDE Book”.

Here are the YouTube videos:

What follows are some excerpts from Point-Of-Care Ultrasound for Emergency Physicians — “The EDE Book”. There is an inexpensive ebook available for Apple devices and I strongly recommend you purchase it right away if you have an Apple device.

Obtaining The Parasternal Long Axis View

Because cardiologists follow a different image orientation scheme than all other sonographers we need to understand the following before getting started:

Echocardiography [meaning cardiologists] have taken a different path from all the rest of the sonography world. Cardiologists perform echo with a phased array probe and the cardiac preset activated. The cardiac preset flips the image [so that the parasternal long axis view points in the opposite direction to what we (meaning POCUS scanners) do – See Learning Ultrasound -5- The Parasternal Long Axis Scan]. However, they perform the SC [subcostal] and the A4C [apical 4 chamber] views with the probe indicator pointed to patient left. In effect, this echo equivalent of a “double negative” means they see the same image that we do when performing the SC and 4AC. In contrast, when they perform a PSL (parasternal long axis), they do so with the indicator pointed to the right as we do. But the echo presets have flipped the image. The result is a mirror image PSL of what we see on the screen in [our cardiac ultrasound scans].

All of the above is well discussed in the article Current issues with emergency cardiac ultrasound probe and image conventions [PubMed Abstract] [Full Text HTML] [Full Text PDF]. Acad Emerg Med. 2008 Mar;15(3):278-84. doi: 10.1111/j.1553-2712.2008.00052.x.

Now on to the scanning technique:

Step 1

The parasternal long axis view begins with the probe being placed immediately adjacent to the left sternal border (i.e., parasternal) with the indicator pointed to the right shoulder. Aim the beam straight toward the back.

The best view in any one patient may be from the 3rd to the 6th intercostal space. Nipple level is the best place to start.

Step 2

Note the view of the heart that you obtained in Step 1. Is it a perfect view? If the answer is yes, then you can skip to Step 3. But if the answer is no, then proceed with Step 2 by sliding the probe between intercostal spaces to compare the views obtained in each of these spaces. The intercaustal space caudad to nipple level is is the next one to choose. It will have a higher yield than sliding cephalad, in good part because the lung is less likely to interfere with your view. If you still do not see the heart well, slide caudad another intercostal space or move to the intercostal space cephalad to the nipple. After having tried more than one intercostal space, return to the space that gave you the best view and then carry on with Step 3.

You may recall that when an echocardiographer performs a PSL view the image is flipped. The apex is pointed to screen left. For this reason, if you select the cardiac preset setting on your ultrasound machine, you may find the image reversed. Just locate and hit a “reverse” or “orient” button on your machine and precede with your scan with the same orientation as all your other scans. Occasionally, you will want to show some pathology to a cardiologist at the bedside.hit the same button so that the image reverses itself again and is more familiar to them.

 

Step 3

Once you have located the best view of the heart at Step 2, you will need to center your Areas of Interest. Although the pericardium is usually centered once the best view is found, the same is not true of the LV and RV. You may need to center differently for each of these Areas of Interest. When the LV is centered, the RV may be cut off on screen left. In this case, you would need to heel the probe medially, aiming the beam under the the sternum to center the RV (Figure 5).

When the RV is centered, too much of the apex can be located beyond screen right. Slide (Figure 6) or the heel (Figure 7) the probe laterally to center the LV.

Step 4

Step 5


Interpretation Of The Cardiac POCUS scans

YouTube has a number of excellent videos that you can review for examples of normal and of depressed left ventricular dysfunction.

 

Resources:

(1) Point-Of-Care Ultrasound for Emergency Physicians — “The EDE Book”; “The clearest and most concise approach to emergency ultrasound.” There is an inexpensive ebook available for Apple devices and I strongly recommend you purchase it right away.

(2) Current issues with emergency cardiac ultrasound probe and image conventions [PubMed Abstract] [Full Text HTML] [Full Text PDF].  2008 Mar;15(3):278-84. doi: 10.1111/j.1553-2712.2008.00052.x.

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