The subxiphoid view of the heart gets a lot of love from scanning protocols such as the FAST exam, but a good parasternal long axis view (PSL) can also yield a large amount of helpful info in just a few seconds.
A good starting point for the PSL is to place the transducer in the fourth intercostal space, just to the left of the patient's sternum. (Image 1.) A cardiac or phased array transducer is best, but you can use any low-frequency probe in a pinch. The direction of the indicator is somewhat a point of contention. I prefer to point the indicator toward the patient's right shoulder. Placing the patient on his left side and moving the transducer in enlarging clockwise circles can also assist with getting a view.
In a “perfect” PSL, the septum should appear almost horizontal, and the apex should not be visible. (Image 2 shown; see video at http://bit.ly/VideosSound.) The chamber of the left ventricle should be full, without papillary muscles or chordae tendineae visible. Shortening the ventricle (viewing it off-axis) can cause a misinterpretation of the contractility. Slightly tilting the transducer toward the right hip or the left shoulder can make a big change in how the chamber looks.
I usually begin by looking for anything that jumps out at me. After looking at enough normal hearts, your eyes will be drawn to something out of place—an enlarged chamber, for example. I look at the left ventricle next. There are two components to normal contractility: The myocardium should thicken by 50 percent in systole, and the chamber should decrease by at least a third. This is usually evident, but bradycardia and tachycardia can fool the eye into thinking the contractility is better or worse than it really is. Pausing your view, scrolling through it frame by frame, and focusing on these components can keep you from being fooled. The excursion, or opening of the valve, is another factor to assess. The anterior mitral leaflet in a normal heart is able to open fully and will often nearly touch the septum. This motion is restricted when the end diastolic volume is increased due to decreased forward flow.
The right ventricle, aortic root, and left atrium should each be about one-third of the area on the right of the image. This is a quick way to look for enlargement of these. Other views offer more information, but this is often a good starting point when right ventricle enlargement is suspected.
Your PSL should have enough depth to see the descending aorta deep to the heart. It is a key marker in assessing the pericardium and differentiating pericardial and pleural fluid collections.
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Dr. Buttsis the director of the division of emergency ultrasound and a clinical associate professor of emergency medicine at Louisiana State University at New Orleans. Follow her on Twitter@EMNSpeedofSound, and read her past columns athttp://bit.ly/EMN-SpeedofSound.